source: draft-ietf-httpbis/01/p5-range.xml @ 165

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set date and version for draft 01

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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "01">
15  <!ENTITY ID-MONTH "January">
16  <!ENTITY ID-YEAR "2008">
17  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY weak-and-strong-validators "<xref target='Part4' x:rel='#weak.and.strong.validators' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19]>
20<?rfc toc="yes" ?>
21<?rfc symrefs="yes" ?>
22<?rfc sortrefs="yes" ?>
23<?rfc compact="yes"?>
24<?rfc subcompact="no" ?>
25<?rfc linkmailto="no" ?>
26<?rfc editing="no" ?>
27<?rfc-ext allow-markup-in-artwork="yes" ?>
28<?rfc-ext include-references-in-index="yes" ?>
29<rfc obsoletes="2616" category="std"
30     ipr="full3978" docName="draft-ietf-httpbis-p5-range-&ID-VERSION;"
31     xmlns:x='http://purl.org/net/xml2rfc/ext'>
32<front>
33
34  <title abbrev="HTTP/1.1, Part 5">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
35
36  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
37    <organization abbrev="Day Software">Day Software</organization>
38    <address>
39      <postal>
40        <street>23 Corporate Plaza DR, Suite 280</street>
41        <city>Newport Beach</city>
42        <region>CA</region>
43        <code>92660</code>
44        <country>USA</country>
45      </postal>
46      <phone>+1-949-706-5300</phone>
47      <facsimile>+1-949-706-5305</facsimile>
48      <email>fielding@gbiv.com</email>
49      <uri>http://roy.gbiv.com/</uri>
50    </address>
51  </author>
52
53  <author initials="J." surname="Gettys" fullname="Jim Gettys">
54    <organization>One Laptop per Child</organization>
55    <address>
56      <postal>
57        <street>21 Oak Knoll Road</street>
58        <city>Carlisle</city>
59        <region>MA</region>
60        <code>01741</code>
61        <country>USA</country>
62      </postal>
63      <email>jg@laptop.org</email>
64      <uri>http://www.laptop.org/</uri>
65    </address>
66  </author>
67 
68  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
69    <organization abbrev="HP">Hewlett-Packard Company</organization>
70    <address>
71      <postal>
72        <street>HP Labs, Large Scale Systems Group</street>
73        <street>1501 Page Mill Road, MS 1177</street>
74        <city>Palo Alto</city>
75        <region>CA</region>
76        <code>94304</code>
77        <country>USA</country>
78      </postal>
79      <email>JeffMogul@acm.org</email>
80    </address>
81  </author>
82
83  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
84    <organization abbrev="Microsoft">Microsoft Corporation</organization>
85    <address>
86      <postal>
87        <street>1 Microsoft Way</street>
88        <city>Redmond</city>
89        <region>WA</region>
90        <code>98052</code>
91        <country>USA</country>
92      </postal>
93      <email>henrikn@microsoft.com</email>
94    </address>
95  </author>
96
97  <author initials="L." surname="Masinter" fullname="Larry Masinter">
98    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
99    <address>
100      <postal>
101        <street>345 Park Ave</street>
102        <city>San Jose</city>
103        <region>CA</region>
104        <code>95110</code>
105        <country>USA</country>
106      </postal>
107      <email>LMM@acm.org</email>
108      <uri>http://larry.masinter.net/</uri>
109    </address>
110  </author>
111 
112  <author initials="P." surname="Leach" fullname="Paul J. Leach">
113    <organization abbrev="Microsoft">Microsoft Corporation</organization>
114    <address>
115      <postal>
116        <street>1 Microsoft Way</street>
117        <city>Redmond</city>
118        <region>WA</region>
119        <code>98052</code>
120      </postal>
121      <email>paulle@microsoft.com</email>
122    </address>
123  </author>
124   
125  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
126    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
127    <address>
128      <postal>
129        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
130        <street>The Stata Center, Building 32</street>
131        <street>32 Vassar Street</street>
132        <city>Cambridge</city>
133        <region>MA</region>
134        <code>02139</code>
135        <country>USA</country>
136      </postal>
137      <email>timbl@w3.org</email>
138      <uri>http://www.w3.org/People/Berners-Lee/</uri>
139    </address>
140  </author>
141
142  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
143    <organization abbrev="W3C">World Wide Web Consortium</organization>
144    <address>
145      <postal>
146        <street>W3C / ERCIM</street>
147        <street>2004, rte des Lucioles</street>
148        <city>Sophia-Antipolis</city>
149        <region>AM</region>
150        <code>06902</code>
151        <country>France</country>
152      </postal>
153      <email>ylafon@w3.org</email>
154      <uri>http://www.raubacapeu.net/people/yves/</uri>
155    </address>
156  </author>
157
158  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
159    <organization abbrev="greenbytes">greenbytes GmbH</organization>
160    <address>
161      <postal>
162        <street>Hafenweg 16</street>
163        <city>Muenster</city><region>NW</region><code>48155</code>
164        <country>Germany</country>
165      </postal>
166      <phone>+49 251 2807760</phone>   
167      <facsimile>+49 251 2807761</facsimile>   
168      <email>julian.reschke@greenbytes.de</email>       
169      <uri>http://greenbytes.de/tech/webdav/</uri>     
170    </address>
171  </author>
172
173  <date month="&ID-MONTH;" year="&ID-YEAR;" day="12"/>
174
175<abstract>
176<t>
177   The Hypertext Transfer Protocol (HTTP) is an application-level
178   protocol for distributed, collaborative, hypermedia information
179   systems. HTTP has been in use by the World Wide Web global information
180   initiative since 1990. This document is Part 5 of the seven-part specification
181   that defines the protocol referred to as "HTTP/1.1" and, taken together,
182   obsoletes RFC 2616.  Part 5 defines range-specific requests and
183   the rules for constructing and combining responses to those requests.
184</t>
185</abstract>
186
187<note title="Editorial Note (To be removed by RFC Editor)">
188  <t>
189    Discussion of this draft should take place on the HTTPBIS working group
190    mailing list (ietf-http-wg@w3.org). The current issues list is
191    at <eref target="http://www.tools.ietf.org/wg/httpbis/trac/report/11"/>
192    and related documents (including fancy diffs) can be found at
193    <eref target="http://www.tools.ietf.org/wg/httpbis/"/>.
194  </t>
195  <t>
196    This draft incorporates those issue resolutions that were either
197    collected in the original RFC2616 errata list (<eref target="http://purl.org/NET/http-errata"/>),
198    or which were agreed upon on the mailing list between October 2006 and
199    November 2007 (as published in "draft-lafon-rfc2616bis-03").
200  </t>
201</note>
202</front>
203<middle>
204<section title="Introduction" anchor="introduction">
205<t>
206   HTTP clients often encounter interrupted data transfers as a result
207   of cancelled requests or dropped connections.  When a cache has stored
208   a partial representation, it is desirable to request the remainder
209   of that representation in a subsequent request rather than transfer
210   the entire representation.
211   There are also a number of Web applications that benefit from being
212   able to request only a subset of a larger representation, such as a
213   single page of a very large document or only part of an image to be
214   rendered by a device with limited local storage.
215</t>
216<t>
217   This document defines HTTP/1.1 range requests,
218   partial responses, and the multipart/byteranges media type.
219   The protocol for range requests is an &OPTIONAL; feature of HTTP,
220   designed so resources or recipients that do not implement this feature
221   can respond as if it is a normal GET request without impacting
222   interoperability.  Partial responses are indicated by a distinct status
223   code to not be mistaken for full responses by intermediate caches
224   that might not implement the feature.
225</t>
226<t>
227   Although the HTTP range request mechanism is designed to allow for
228   extensible range types, this specification only defines requests for
229   byte ranges.
230</t>
231
232<section title="Requirements" anchor="intro.requirements">
233<t>
234   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
235   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
236   document are to be interpreted as described in <xref target="RFC2119"/>.
237</t>
238<t>
239   An implementation is not compliant if it fails to satisfy one or more
240   of the &MUST; or &REQUIRED; level requirements for the protocols it
241   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
242   level and all the &SHOULD; level requirements for its protocols is said
243   to be "unconditionally compliant"; one that satisfies all the &MUST;
244   level requirements but not all the &SHOULD; level requirements for its
245   protocols is said to be "conditionally compliant."
246</t>
247</section>
248</section>
249
250<section title="Range Units" anchor="range.units">
251<t>
252   HTTP/1.1 allows a client to request that only part (a range of) the
253   response entity be included within the response. HTTP/1.1 uses range
254   units in the Range (<xref target="header.range"/>) and Content-Range (<xref target="header.content-range"/>)
255   header fields. An entity can be broken down into subranges according
256   to various structural units.
257</t>
258<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"/>
259  range-unit       = bytes-unit | other-range-unit
260  bytes-unit       = "bytes"
261  other-range-unit = token
262</artwork></figure>
263<t>
264   The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1
265   implementations &MAY; ignore ranges specified using other units.
266</t>
267<t>
268   HTTP/1.1 has been designed to allow implementations of applications
269   that do not depend on knowledge of ranges.
270</t>
271</section>
272
273<section title="Status Code Definitions">
274<section title="206 Partial Content" anchor="status.206">
275  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
276  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
277<t>
278   The server has fulfilled the partial GET request for the resource.
279   The request &MUST; have included a Range header field (<xref target="header.range"/>)
280   indicating the desired range, and &MAY; have included an If-Range
281   header field (<xref target="header.if-range"/>) to make the request conditional.
282</t>
283<t>
284   The response &MUST; include the following header fields:
285  <list style="symbols">
286    <t>
287        Either a Content-Range header field (<xref target="header.content-range"/>) indicating
288        the range included with this response, or a multipart/byteranges
289        Content-Type including Content-Range fields for each part. If a
290        Content-Length header field is present in the response, its
291        value &MUST; match the actual number of OCTETs transmitted in the
292        message-body.
293    </t>
294    <t>
295        Date
296    </t>
297    <t>
298        ETag and/or Content-Location, if the header would have been sent
299        in a 200 response to the same request
300    </t>
301    <t>
302        Expires, Cache-Control, and/or Vary, if the field-value might
303        differ from that sent in any previous response for the same
304        variant
305    </t>
306  </list>
307</t>
308<t>
309   If the 206 response is the result of an If-Range request, the response
310   &SHOULD-NOT; include other entity-headers. Otherwise, the response
311   &MUST; include all of the entity-headers that would have been returned
312   with a 200 (OK) response to the same request.
313</t>
314<t>
315   A cache &MUST-NOT; combine a 206 response with other previously cached
316   content if the ETag or Last-Modified headers do not match exactly,
317   see <xref target="combining.byte.ranges"/>.
318</t>
319<t>
320   A cache that does not support the Range and Content-Range headers
321   &MUST-NOT; cache 206 (Partial Content) responses.
322</t>
323</section>
324
325<section title="416 Requested Range Not Satisfiable" anchor="status.416">
326  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
327  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
328<t>
329   A server &SHOULD; return a response with this status code if a request
330   included a Range request-header field (<xref target="header.range"/>), and none of
331   the range-specifier values in this field overlap the current extent
332   of the selected resource, and the request did not include an If-Range
333   request-header field. (For byte-ranges, this means that the first-byte-pos
334   of all of the byte-range-spec values were greater than the
335   current length of the selected resource.)
336</t>
337<t>
338   When this status code is returned for a byte-range request, the
339   response &SHOULD; include a Content-Range entity-header field
340   specifying the current length of the selected resource (see <xref target="header.content-range"/>).
341   This response &MUST-NOT; use the multipart/byteranges content-type.
342</t>
343</section>
344</section>
345
346<section title="Combining Byte Ranges" anchor="combining.byte.ranges">
347<t>
348   A response might transfer only a subrange of the bytes of an entity-body,
349   either because the request included one or more Range
350   specifications, or because a connection was broken prematurely. After
351   several such transfers, a cache might have received several ranges of
352   the same entity-body.
353</t>
354<t>
355   If a cache has a stored non-empty set of subranges for an entity, and
356   an incoming response transfers another subrange, the cache &MAY;
357   combine the new subrange with the existing set if both the following
358   conditions are met:
359  <list style="symbols">
360    <t>Both the incoming response and the cache entry have a cache
361        validator.</t>
362    <t>The two cache validators match using the strong comparison
363        function (see &weak-and-strong-validators;).</t>
364  </list>
365</t>
366<t>
367   If either requirement is not met, the cache &MUST; use only the most
368   recent partial response (based on the Date values transmitted with
369   every response, and using the incoming response if these values are
370   equal or missing), and &MUST; discard the other partial information.
371</t>
372</section>
373
374<section title="Header Field Definitions" anchor="header.fields">
375<t>
376   This section defines the syntax and semantics of HTTP/1.1 header fields
377   related to range requests and partial responses.
378</t>
379<t>
380   For entity-header fields, both sender and recipient refer to either the
381   client or the server, depending on who sends and who receives the entity.
382</t>
383
384<section title="Accept-Ranges" anchor="header.accept-ranges">
385  <iref primary="true" item="Accept-Ranges header" x:for-anchor=""/>
386  <iref primary="true" item="Headers" subitem="Accept-Ranges" x:for-anchor=""/>
387<t>
388      The Accept-Ranges response-header field allows the server to
389      indicate its acceptance of range requests for a resource:
390</t>
391<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Ranges"/><iref primary="true" item="Grammar" subitem="acceptable-ranges"/>
392  Accept-Ranges     = "Accept-Ranges" ":" acceptable-ranges
393  acceptable-ranges = 1#range-unit | "none"
394</artwork></figure>
395<t>
396      Origin servers that accept byte-range requests &MAY; send
397</t>
398<figure><artwork type="example">
399       Accept-Ranges: bytes
400</artwork></figure>
401<t>
402      but are not required to do so. Clients &MAY; generate byte-range
403      requests without having received this header for the resource
404      involved. Range units are defined in <xref target="range.units"/>.
405</t>
406<t>
407      Servers that do not accept any kind of range request for a
408      resource &MAY; send
409</t>
410<figure><artwork type="example">
411       Accept-Ranges: none
412</artwork></figure>
413<t>
414      to advise the client not to attempt a range request.
415</t>
416</section>
417
418<section title="Content-Range" anchor="header.content-range">
419  <iref primary="true" item="Content-Range header" x:for-anchor=""/>
420  <iref primary="true" item="Headers" subitem="Content-Range" x:for-anchor=""/>
421<t>
422   The Content-Range entity-header is sent with a partial entity-body to
423   specify where in the full entity-body the partial body should be
424   applied. Range units are defined in <xref target="range.units"/>.
425</t>
426<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Range"/><iref primary="true" item="Grammar" subitem="content-range-spec"/><iref primary="true" item="Grammar" subitem="byte-content-range-spec"/><iref primary="true" item="Grammar" subitem="byte-range-resp-spec"/><iref primary="true" item="Grammar" subitem="instance-length"/>
427  Content-Range = "Content-Range" ":" content-range-spec
428 
429  content-range-spec      = byte-content-range-spec
430  byte-content-range-spec = bytes-unit SP
431                            byte-range-resp-spec "/"
432                            ( instance-length | "*" )
433 
434  byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)
435                                 | "*"
436  instance-length           = 1*DIGIT
437</artwork></figure>
438<t>
439   The header &SHOULD; indicate the total length of the full entity-body,
440   unless this length is unknown or difficult to determine. The asterisk
441   "*" character means that the instance-length is unknown at the time
442   when the response was generated.
443</t>
444<t>
445   Unlike byte-ranges-specifier values (see <xref target="byte.ranges"/>), a byte-range-resp-spec
446   &MUST; only specify one range, and &MUST; contain
447   absolute byte positions for both the first and last byte of the
448   range.
449</t>
450<t>
451   A byte-content-range-spec with a byte-range-resp-spec whose last-byte-pos
452   value is less than its first-byte-pos value, or whose
453   instance-length value is less than or equal to its last-byte-pos
454   value, is invalid. The recipient of an invalid byte-content-range-spec
455   &MUST; ignore it and any content transferred along with it.
456</t>
457<t>
458   A server sending a response with status code 416 (Requested range not
459   satisfiable) &SHOULD; include a Content-Range field with a byte-range-resp-spec
460   of "*". The instance-length specifies the current length of
461   the selected resource. A response with status code 206 (Partial
462   Content) &MUST-NOT; include a Content-Range field with a byte-range-resp-spec of "*".
463</t>
464<t>
465   Examples of byte-content-range-spec values, assuming that the entity
466   contains a total of 1234 bytes:
467   <list style="symbols">
468      <t>
469        The first 500 bytes:
470<figure><artwork type="text/plain">
471   bytes 0-499/1234
472</artwork></figure>
473      </t>   
474      <t>
475        The second 500 bytes:
476<figure><artwork type="text/plain">
477   bytes 500-999/1234
478</artwork></figure>
479      </t>   
480      <t>
481        All except for the first 500 bytes:
482<figure><artwork type="text/plain">
483   bytes 500-1233/1234
484</artwork></figure>
485      </t>   
486      <t>
487        The last 500 bytes:
488<figure><artwork type="text/plain">
489   bytes 734-1233/1234
490</artwork></figure>
491      </t>   
492   </list>
493</t>
494<t>
495   When an HTTP message includes the content of a single range (for
496   example, a response to a request for a single range, or to a request
497   for a set of ranges that overlap without any holes), this content is
498   transmitted with a Content-Range header, and a Content-Length header
499   showing the number of bytes actually transferred. For example,
500</t>
501<figure><artwork type="example">
502    HTTP/1.1 206 Partial Content
503    Date: Wed, 15 Nov 1995 06:25:24 GMT
504    Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
505    Content-Range: bytes 21010-47021/47022
506    Content-Length: 26012
507    Content-Type: image/gif
508</artwork></figure>
509<t>
510   When an HTTP message includes the content of multiple ranges (for
511   example, a response to a request for multiple non-overlapping
512   ranges), these are transmitted as a multipart message. The multipart
513   media type used for this purpose is "multipart/byteranges" as defined
514   in <xref target="internet.media.type.multipart.byteranges"/>. See <xref target="changes.from.rfc.2068"/> for a compatibility issue.
515</t>
516<t>
517   A response to a request for a single range &MUST-NOT; be sent using the
518   multipart/byteranges media type.  A response to a request for
519   multiple ranges, whose result is a single range, &MAY; be sent as a
520   multipart/byteranges media type with one part. A client that cannot
521   decode a multipart/byteranges message &MUST-NOT; ask for multiple
522   byte-ranges in a single request.
523</t>
524<t>
525   When a client requests multiple byte-ranges in one request, the
526   server &SHOULD; return them in the order that they appeared in the
527   request.
528</t>
529<t>
530   If the server ignores a byte-range-spec because it is syntactically
531   invalid, the server &SHOULD; treat the request as if the invalid Range
532   header field did not exist. (Normally, this means return a 200
533   response containing the full entity).
534</t>
535<t>
536   If the server receives a request (other than one including an If-Range
537   request-header field) with an unsatisfiable Range request-header
538   field (that is, all of whose byte-range-spec values have a
539   first-byte-pos value greater than the current length of the selected
540   resource), it &SHOULD; return a response code of 416 (Requested range
541   not satisfiable) (<xref target="status.416"/>).
542  <list><t>
543      <x:h>Note:</x:h> clients cannot depend on servers to send a 416 (Requested
544      range not satisfiable) response instead of a 200 (OK) response for
545      an unsatisfiable Range request-header, since not all servers
546      implement this request-header.
547  </t></list>
548</t>
549</section>
550
551<section title="If-Range" anchor="header.if-range">
552  <iref primary="true" item="If-Range header" x:for-anchor=""/>
553  <iref primary="true" item="Headers" subitem="If-Range" x:for-anchor=""/>
554<t>
555   If a client has a partial copy of an entity in its cache, and wishes
556   to have an up-to-date copy of the entire entity in its cache, it
557   could use the Range request-header with a conditional GET (using
558   either or both of If-Unmodified-Since and If-Match.) However, if the
559   condition fails because the entity has been modified, the client
560   would then have to make a second request to obtain the entire current
561   entity-body.
562</t>
563<t>
564   The If-Range header allows a client to "short-circuit" the second
565   request. Informally, its meaning is `if the entity is unchanged, send
566   me the part(s) that I am missing; otherwise, send me the entire new
567   entity'.
568</t>
569<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-Range"/>
570  If-Range = "If-Range" ":" ( entity-tag | HTTP-date )
571</artwork></figure>
572<t>
573   If the client has no entity tag for an entity, but does have a Last-Modified
574   date, it &MAY; use that date in an If-Range header. (The
575   server can distinguish between a valid HTTP-date and any form of
576   entity-tag by examining no more than two characters.) The If-Range
577   header &SHOULD; only be used together with a Range header, and &MUST; be
578   ignored if the request does not include a Range header, or if the
579   server does not support the sub-range operation.
580</t>
581<t>
582   If the entity tag given in the If-Range header matches the current
583   entity tag for the entity, then the server &SHOULD; provide the
584   specified sub-range of the entity using a 206 (Partial Content)
585   response. If the entity tag does not match, then the server &SHOULD;
586   return the entire entity using a 200 (OK) response.
587</t>
588</section>
589
590<section title="Range" anchor="header.range">
591  <iref primary="true" item="Range header" x:for-anchor=""/>
592  <iref primary="true" item="Headers" subitem="Range" x:for-anchor=""/>
593
594<section title="Byte Ranges" anchor="byte.ranges">
595<t>
596   Since all HTTP entities are represented in HTTP messages as sequences
597   of bytes, the concept of a byte range is meaningful for any HTTP
598   entity. (However, not all clients and servers need to support byte-range
599   operations.)
600</t>
601<t>
602   Byte range specifications in HTTP apply to the sequence of bytes in
603   the entity-body (not necessarily the same as the message-body).
604</t>
605<t>
606   A byte range operation &MAY; specify a single range of bytes, or a set
607   of ranges within a single entity.
608</t>
609<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"/>
610  ranges-specifier = byte-ranges-specifier
611  byte-ranges-specifier = bytes-unit "=" byte-range-set
612  byte-range-set  = 1#( byte-range-spec | suffix-byte-range-spec )
613  byte-range-spec = first-byte-pos "-" [last-byte-pos]
614  first-byte-pos  = 1*DIGIT
615  last-byte-pos   = 1*DIGIT
616</artwork></figure>
617<t>
618   The first-byte-pos value in a byte-range-spec gives the byte-offset
619   of the first byte in a range. The last-byte-pos value gives the
620   byte-offset of the last byte in the range; that is, the byte
621   positions specified are inclusive. Byte offsets start at zero.
622</t>
623<t>
624   If the last-byte-pos value is present, it &MUST; be greater than or
625   equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec
626   is syntactically invalid. The recipient of a byte-range-set
627   that includes one or more syntactically invalid byte-range-spec
628   values &MUST; ignore the header field that includes that byte-range-set.
629</t>
630<t>
631   If the last-byte-pos value is absent, or if the value is greater than
632   or equal to the current length of the entity-body, last-byte-pos is
633   taken to be equal to one less than the current length of the entity-body
634   in bytes.
635</t>
636<t>
637   By its choice of last-byte-pos, a client can limit the number of
638   bytes retrieved without knowing the size of the entity.
639</t>
640<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="suffix-byte-range-spec"/><iref primary="true" item="Grammar" subitem="suffix-length"/>
641  suffix-byte-range-spec = "-" suffix-length
642  suffix-length = 1*DIGIT
643</artwork></figure>
644<t>
645   A suffix-byte-range-spec is used to specify the suffix of the
646   entity-body, of a length given by the suffix-length value. (That is,
647   this form specifies the last N bytes of an entity-body.) If the
648   entity is shorter than the specified suffix-length, the entire
649   entity-body is used.
650</t>
651<t>
652   If a syntactically valid byte-range-set includes at least one byte-range-spec
653   whose first-byte-pos is less than the current length of
654   the entity-body, or at least one suffix-byte-range-spec with a non-zero
655   suffix-length, then the byte-range-set is satisfiable.
656   Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set
657   is unsatisfiable, the server &SHOULD; return a response with a status
658   of 416 (Requested range not satisfiable). Otherwise, the server
659   &SHOULD; return a response with a status of 206 (Partial Content)
660   containing the satisfiable ranges of the entity-body.
661</t>
662<t>
663   Examples of byte-ranges-specifier values (assuming an entity-body of
664   length 10000):
665  <list style="symbols">
666     <t>The first 500 bytes (byte offsets 0-499, inclusive):  bytes=0-499</t>
667
668     <t>The second 500 bytes (byte offsets 500-999, inclusive):
669        bytes=500-999</t>
670
671     <t>The final 500 bytes (byte offsets 9500-9999, inclusive):
672        bytes=-500</t>
673
674     <t>Or bytes=9500-</t>
675
676     <t>The first and last bytes only (bytes 0 and 9999):  bytes=0-0,-1</t>
677
678     <t>Several legal but not canonical specifications of the second 500
679        bytes (byte offsets 500-999, inclusive):
680        <vspace/>
681         bytes=500-600,601-999<vspace/>
682         bytes=500-700,601-999</t>
683  </list>
684</t>
685</section>
686
687<section title="Range Retrieval Requests" anchor="range.retrieval.requests">
688<t>
689   HTTP retrieval requests using conditional or unconditional GET
690   methods &MAY; request one or more sub-ranges of the entity, instead of
691   the entire entity, using the Range request header, which applies to
692   the entity returned as the result of the request:
693</t>
694<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Range"/>
695  Range = "Range" ":" ranges-specifier
696</artwork></figure>
697<t>
698   A server &MAY; ignore the Range header. However, HTTP/1.1 origin
699   servers and intermediate caches ought to support byte ranges when
700   possible, since Range supports efficient recovery from partially
701   failed transfers, and supports efficient partial retrieval of large
702   entities.
703</t>
704<t>
705   If the server supports the Range header and the specified range or
706   ranges are appropriate for the entity:
707  <list style="symbols">
708     <t>The presence of a Range header in an unconditional GET modifies
709        what is returned if the GET is otherwise successful. In other
710        words, the response carries a status code of 206 (Partial
711        Content) instead of 200 (OK).</t>
712
713     <t>The presence of a Range header in a conditional GET (a request
714        using one or both of If-Modified-Since and If-None-Match, or
715        one or both of If-Unmodified-Since and If-Match) modifies what
716        is returned if the GET is otherwise successful and the
717        condition is true. It does not affect the 304 (Not Modified)
718        response returned if the conditional is false.</t>
719  </list>
720</t>
721<t>
722   In some cases, it might be more appropriate to use the If-Range
723   header (see <xref target="header.if-range"/>) in addition to the Range header.
724</t>
725<t>
726   If a proxy that supports ranges receives a Range request, forwards
727   the request to an inbound server, and receives an entire entity in
728   reply, it &SHOULD; only return the requested range to its client. It
729   &SHOULD; store the entire received response in its cache if that is
730   consistent with its cache allocation policies.
731</t>
732</section>
733</section>
734</section>
735
736<section title="IANA Considerations" anchor="IANA.considerations">
737<t>
738   TBD.
739</t>
740</section>
741
742<section title="Security Considerations" anchor="security.considerations">
743<t>
744   No additional security considerations have been identified beyond
745   those applicable to HTTP in general &messaging;.
746</t>
747</section>
748
749<section title="Acknowledgments" anchor="ack">
750<t>
751   Most of the specification of ranges is based on work originally done
752   by Ari Luotonen and John Franks, with additional input from Steve
753   Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin Hamilton,
754   Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz, Larry Masinter,
755   Jeff Mogul, Lou Montulli, David W. Morris, Luigi Rizzo, and Bill Weihl.
756</t>
757</section>
758</middle>
759<back>
760
761<references title="Normative References">
762
763<reference anchor="Part1">
764  <front>
765    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
766    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
767      <organization abbrev="Day Software">Day Software</organization>
768      <address><email>fielding@gbiv.com</email></address>
769    </author>
770    <author initials="J." surname="Gettys" fullname="Jim Gettys">
771      <organization>One Laptop per Child</organization>
772      <address><email>jg@laptop.org</email></address>
773    </author>
774    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
775      <organization abbrev="HP">Hewlett-Packard Company</organization>
776      <address><email>JeffMogul@acm.org</email></address>
777    </author>
778    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
779      <organization abbrev="Microsoft">Microsoft Corporation</organization>
780      <address><email>henrikn@microsoft.com</email></address>
781    </author>
782    <author initials="L." surname="Masinter" fullname="Larry Masinter">
783      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
784      <address><email>LMM@acm.org</email></address>
785    </author>
786    <author initials="P." surname="Leach" fullname="Paul J. Leach">
787      <organization abbrev="Microsoft">Microsoft Corporation</organization>
788      <address><email>paulle@microsoft.com</email></address>
789    </author>
790    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
791      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
792      <address><email>timbl@w3.org</email></address>
793    </author>
794    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
795      <organization abbrev="W3C">World Wide Web Consortium</organization>
796      <address><email>ylafon@w3.org</email></address>
797    </author>
798    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
799      <organization abbrev="greenbytes">greenbytes GmbH</organization>
800      <address><email>julian.reschke@greenbytes.de</email></address>
801    </author>
802    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
803  </front>
804  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
805  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
806</reference>
807
808<reference anchor="Part3">
809  <front>
810    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
811    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
812      <organization abbrev="Day Software">Day Software</organization>
813      <address><email>fielding@gbiv.com</email></address>
814    </author>
815    <author initials="J." surname="Gettys" fullname="Jim Gettys">
816      <organization>One Laptop per Child</organization>
817      <address><email>jg@laptop.org</email></address>
818    </author>
819    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
820      <organization abbrev="HP">Hewlett-Packard Company</organization>
821      <address><email>JeffMogul@acm.org</email></address>
822    </author>
823    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
824      <organization abbrev="Microsoft">Microsoft Corporation</organization>
825      <address><email>henrikn@microsoft.com</email></address>
826    </author>
827    <author initials="L." surname="Masinter" fullname="Larry Masinter">
828      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
829      <address><email>LMM@acm.org</email></address>
830    </author>
831    <author initials="P." surname="Leach" fullname="Paul J. Leach">
832      <organization abbrev="Microsoft">Microsoft Corporation</organization>
833      <address><email>paulle@microsoft.com</email></address>
834    </author>
835    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
836      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
837      <address><email>timbl@w3.org</email></address>
838    </author>
839    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
840      <organization abbrev="W3C">World Wide Web Consortium</organization>
841      <address><email>ylafon@w3.org</email></address>
842    </author>
843    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
844      <organization abbrev="greenbytes">greenbytes GmbH</organization>
845      <address><email>julian.reschke@greenbytes.de</email></address>
846    </author>
847    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
848  </front>
849  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
850  <x:source href="p3-payload.xml" basename="p3-payload"/>
851</reference>
852
853<reference anchor="Part4">
854  <front>
855    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
856    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
857      <organization abbrev="Day Software">Day Software</organization>
858      <address><email>fielding@gbiv.com</email></address>
859    </author>
860    <author initials="J." surname="Gettys" fullname="Jim Gettys">
861      <organization>One Laptop per Child</organization>
862      <address><email>jg@laptop.org</email></address>
863    </author>
864    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
865      <organization abbrev="HP">Hewlett-Packard Company</organization>
866      <address><email>JeffMogul@acm.org</email></address>
867    </author>
868    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
869      <organization abbrev="Microsoft">Microsoft Corporation</organization>
870      <address><email>henrikn@microsoft.com</email></address>
871    </author>
872    <author initials="L." surname="Masinter" fullname="Larry Masinter">
873      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
874      <address><email>LMM@acm.org</email></address>
875    </author>
876    <author initials="P." surname="Leach" fullname="Paul J. Leach">
877      <organization abbrev="Microsoft">Microsoft Corporation</organization>
878      <address><email>paulle@microsoft.com</email></address>
879    </author>
880    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
881      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
882      <address><email>timbl@w3.org</email></address>
883    </author>
884    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
885      <organization abbrev="W3C">World Wide Web Consortium</organization>
886      <address><email>ylafon@w3.org</email></address>
887    </author>
888    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
889      <organization abbrev="greenbytes">greenbytes GmbH</organization>
890      <address><email>julian.reschke@greenbytes.de</email></address>
891    </author>
892    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
893  </front>
894  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
895  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
896</reference>
897
898<reference anchor="Part6">
899  <front>
900    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
901    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
902      <organization abbrev="Day Software">Day Software</organization>
903      <address><email>fielding@gbiv.com</email></address>
904    </author>
905    <author initials="J." surname="Gettys" fullname="Jim Gettys">
906      <organization>One Laptop per Child</organization>
907      <address><email>jg@laptop.org</email></address>
908    </author>
909    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
910      <organization abbrev="HP">Hewlett-Packard Company</organization>
911      <address><email>JeffMogul@acm.org</email></address>
912    </author>
913    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
914      <organization abbrev="Microsoft">Microsoft Corporation</organization>
915      <address><email>henrikn@microsoft.com</email></address>
916    </author>
917    <author initials="L." surname="Masinter" fullname="Larry Masinter">
918      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
919      <address><email>LMM@acm.org</email></address>
920    </author>
921    <author initials="P." surname="Leach" fullname="Paul J. Leach">
922      <organization abbrev="Microsoft">Microsoft Corporation</organization>
923      <address><email>paulle@microsoft.com</email></address>
924    </author>
925    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
926      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
927      <address><email>timbl@w3.org</email></address>
928    </author>
929    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
930      <organization abbrev="W3C">World Wide Web Consortium</organization>
931      <address><email>ylafon@w3.org</email></address>
932    </author>
933    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
934      <organization abbrev="greenbytes">greenbytes GmbH</organization>
935      <address><email>julian.reschke@greenbytes.de</email></address>
936    </author>
937    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
938  </front>
939  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
940  <x:source href="p6-cache.xml" basename="p6-cache"/>
941</reference>
942
943<reference anchor="RFC2046">
944  <front>
945    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
946    <author initials="N." surname="Freed" fullname="Ned Freed">
947      <organization>Innosoft International, Inc.</organization>
948      <address><email>ned@innosoft.com</email></address>
949    </author>
950    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
951      <organization>First Virtual Holdings</organization>
952      <address><email>nsb@nsb.fv.com</email></address>
953    </author>
954    <date month="November" year="1996"/>
955  </front>
956  <seriesInfo name="RFC" value="2046"/>
957</reference>
958
959<reference anchor="RFC2119">
960  <front>
961    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
962    <author initials="S." surname="Bradner" fullname="Scott Bradner">
963      <organization>Harvard University</organization>
964      <address><email>sob@harvard.edu</email></address>
965    </author>
966    <date month="March" year="1997"/>
967  </front>
968  <seriesInfo name="BCP" value="14"/>
969  <seriesInfo name="RFC" value="2119"/>
970</reference>
971
972</references>
973
974<references title="Informative References">
975
976<reference anchor="RFC2616">
977  <front>
978    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
979    <author initials="R." surname="Fielding" fullname="R. Fielding">
980      <organization>University of California, Irvine</organization>
981      <address><email>fielding@ics.uci.edu</email></address>
982    </author>
983    <author initials="J." surname="Gettys" fullname="J. Gettys">
984      <organization>W3C</organization>
985      <address><email>jg@w3.org</email></address>
986    </author>
987    <author initials="J." surname="Mogul" fullname="J. Mogul">
988      <organization>Compaq Computer Corporation</organization>
989      <address><email>mogul@wrl.dec.com</email></address>
990    </author>
991    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
992      <organization>MIT Laboratory for Computer Science</organization>
993      <address><email>frystyk@w3.org</email></address>
994    </author>
995    <author initials="L." surname="Masinter" fullname="L. Masinter">
996      <organization>Xerox Corporation</organization>
997      <address><email>masinter@parc.xerox.com</email></address>
998    </author>
999    <author initials="P." surname="Leach" fullname="P. Leach">
1000      <organization>Microsoft Corporation</organization>
1001      <address><email>paulle@microsoft.com</email></address>
1002    </author>
1003    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
1004      <organization>W3C</organization>
1005      <address><email>timbl@w3.org</email></address>
1006    </author>
1007    <date month="June" year="1999"/>
1008  </front>
1009  <seriesInfo name="RFC" value="2616"/>
1010</reference>
1011
1012</references>
1013
1014<section title="Internet Media Type multipart/byteranges" anchor="internet.media.type.multipart.byteranges">
1015<iref item="Media Type" subitem="multipart/byteranges" primary="true"/>
1016<iref item="multipart/byteranges Media Type" primary="true"/>
1017<t>
1018   When an HTTP 206 (Partial Content) response message includes the
1019   content of multiple ranges (a response to a request for multiple
1020   non-overlapping ranges), these are transmitted as a multipart
1021   message-body. The media type for this purpose is called
1022   "multipart/byteranges".
1023</t><t>
1024   The multipart/byteranges media type includes two or more parts, each
1025   with its own Content-Type and Content-Range fields. The required
1026   boundary parameter specifies the boundary string used to separate
1027   each body-part.
1028</t>
1029<t>
1030  <list style="hanging" x:indent="12em">
1031    <t hangText="Media Type name:">
1032      multipart
1033    </t>
1034    <t hangText="Media subtype name:">
1035      byteranges
1036    </t>
1037    <t hangText="Required parameters:">
1038      boundary
1039    </t>
1040    <t hangText="Optional parameters:">
1041      none
1042    </t>
1043    <t hangText="Encoding considerations:">
1044      only "7bit", "8bit", or "binary" are permitted
1045    </t>
1046    <t hangText="Security considerations:">
1047      none
1048    </t>
1049  </list>
1050</t>
1051<figure><preamble>
1052   For example:
1053</preamble><artwork type="example">
1054   HTTP/1.1 206 Partial Content
1055   Date: Wed, 15 Nov 1995 06:25:24 GMT
1056   Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1057   Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1058
1059   --THIS_STRING_SEPARATES
1060   Content-type: application/pdf
1061   Content-range: bytes 500-999/8000
1062
1063   ...the first range...
1064   --THIS_STRING_SEPARATES
1065   Content-type: application/pdf
1066   Content-range: bytes 7000-7999/8000
1067
1068   ...the second range
1069   --THIS_STRING_SEPARATES--
1070</artwork></figure>
1071<t>
1072      Notes:
1073  <list style="numbers">
1074      <t>Additional CRLFs may precede the first boundary string in the
1075         entity.</t>
1076
1077      <t>Although <xref target="RFC2046"/> permits the boundary string to be
1078         quoted, some existing implementations handle a quoted boundary
1079         string incorrectly.</t>
1080
1081      <t>A number of browsers and servers were coded to an early draft
1082         of the byteranges specification to use a media type of
1083         multipart/x-byteranges<iref item="multipart/x-byteranges Media Type"/><iref item="Media Type" subitem="multipart/x-byteranges"/>, which is almost, but not quite
1084         compatible with the version documented in HTTP/1.1.</t>
1085  </list>
1086</t>
1087</section>
1088
1089<section title="Compatibility with Previous Versions" anchor="compatibility">
1090<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
1091<t>
1092   Transfer-coding and message lengths all interact in ways that
1093   required fixing exactly when chunked encoding is used (to allow for
1094   transfer encoding that may not be self delimiting); it was important
1095   to straighten out exactly how message lengths are computed.
1096   (<xref target="header.content-range"/>,
1097   see also <xref target="Part1"/>, <xref target="Part3"/> and <xref target="Part6"/>)
1098</t>
1099<t>
1100   There are situations where a server (especially a proxy) does not
1101   know the full length of a response but is capable of serving a
1102   byterange request. We therefore need a mechanism to allow byteranges
1103   with a content-range not indicating the full length of the message.
1104   (<xref target="header.content-range"/>)
1105</t>
1106<t>
1107   Range request responses would become very verbose if all meta-data
1108   were always returned; by allowing the server to only send needed
1109   headers in a 206 response, this problem can be avoided.
1110   (Section <xref target="status.206" format="counter"/>
1111   and <xref target="header.if-range" format="counter"/>)
1112</t>
1113<t>
1114   Fix problem with unsatisfiable range requests; there are two cases:
1115   syntactic problems, and range doesn't exist in the document. The 416
1116   status code was needed to resolve this ambiguity needed to indicate
1117   an error for a byte range request that falls outside of the actual
1118   contents of a document. (Section <xref target="status.416" format="counter"/>, <xref target="header.content-range" format="counter"/>)
1119</t>
1120</section>
1121
1122<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
1123<t>
1124  Clarify that it is not ok to use a weak cache validator in a 206 response.
1125  (<xref target="status.206"/>)
1126</t>
1127</section>
1128
1129</section>
1130
1131<section title="Change Log (to be removed by RFC Editor before publication)">
1132
1133<section title="Since RFC2616">
1134<t>
1135  Extracted relevant partitions from <xref target="RFC2616"/>.
1136</t>
1137</section>
1138
1139<section title="Since draft-ietf-httpbis-p5-range-00">
1140<t>
1141  Closed issues:
1142  <list style="symbols"> 
1143    <t>
1144      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/18"/>:
1145      "Cache validators in 206 responses"
1146      (<eref target="http://purl.org/NET/http-errata#ifrange206"/>)
1147    </t>
1148    <t>
1149      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
1150      "Normative and Informative references"
1151    </t>
1152    <t>
1153      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
1154      "Normative up-to-date references"
1155    </t>
1156  </list>
1157</t>
1158</section>
1159
1160</section>
1161
1162</back>
1163</rfc>
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