source: draft-ietf-httpbis/latest/p5-range.xml @ 363

Last change on this file since 363 was 363, checked in by julian.reschke@…, 11 years ago

Rewrite header ABNFs to spell out whitespace rules, factor out value format definitions. (related to #36)

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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "November">
16  <!ENTITY ID-YEAR "2008">
17  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY full-date                  "<xref target='Part1' x:rel='#full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY entity-tags                "<xref target='Part4' x:rel='#entity.tags' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY weak-and-strong-validators "<xref target='Part4' x:rel='#weak.and.strong.validators' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23]>
24<?rfc toc="yes" ?>
25<?rfc symrefs="yes" ?>
26<?rfc sortrefs="yes" ?>
27<?rfc compact="yes"?>
28<?rfc subcompact="no" ?>
29<?rfc linkmailto="no" ?>
30<?rfc editing="no" ?>
31<?rfc comments="yes"?>
32<?rfc inline="yes"?>
33<?rfc-ext allow-markup-in-artwork="yes" ?>
34<?rfc-ext include-references-in-index="yes" ?>
35<rfc obsoletes="2616" category="std" x:maturity-level="draft"
36     ipr="full3978" docName="draft-ietf-httpbis-p5-range-&ID-VERSION;"
37     xmlns:x='http://purl.org/net/xml2rfc/ext'>
38<front>
39
40  <title abbrev="HTTP/1.1, Part 5">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
41
42  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
43    <organization abbrev="Day Software">Day Software</organization>
44    <address>
45      <postal>
46        <street>23 Corporate Plaza DR, Suite 280</street>
47        <city>Newport Beach</city>
48        <region>CA</region>
49        <code>92660</code>
50        <country>USA</country>
51      </postal>
52      <phone>+1-949-706-5300</phone>
53      <facsimile>+1-949-706-5305</facsimile>
54      <email>fielding@gbiv.com</email>
55      <uri>http://roy.gbiv.com/</uri>
56    </address>
57  </author>
58
59  <author initials="J." surname="Gettys" fullname="Jim Gettys">
60    <organization>One Laptop per Child</organization>
61    <address>
62      <postal>
63        <street>21 Oak Knoll Road</street>
64        <city>Carlisle</city>
65        <region>MA</region>
66        <code>01741</code>
67        <country>USA</country>
68      </postal>
69      <email>jg@laptop.org</email>
70      <uri>http://www.laptop.org/</uri>
71    </address>
72  </author>
73 
74  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
75    <organization abbrev="HP">Hewlett-Packard Company</organization>
76    <address>
77      <postal>
78        <street>HP Labs, Large Scale Systems Group</street>
79        <street>1501 Page Mill Road, MS 1177</street>
80        <city>Palo Alto</city>
81        <region>CA</region>
82        <code>94304</code>
83        <country>USA</country>
84      </postal>
85      <email>JeffMogul@acm.org</email>
86    </address>
87  </author>
88
89  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
90    <organization abbrev="Microsoft">Microsoft Corporation</organization>
91    <address>
92      <postal>
93        <street>1 Microsoft Way</street>
94        <city>Redmond</city>
95        <region>WA</region>
96        <code>98052</code>
97        <country>USA</country>
98      </postal>
99      <email>henrikn@microsoft.com</email>
100    </address>
101  </author>
102
103  <author initials="L." surname="Masinter" fullname="Larry Masinter">
104    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
105    <address>
106      <postal>
107        <street>345 Park Ave</street>
108        <city>San Jose</city>
109        <region>CA</region>
110        <code>95110</code>
111        <country>USA</country>
112      </postal>
113      <email>LMM@acm.org</email>
114      <uri>http://larry.masinter.net/</uri>
115    </address>
116  </author>
117 
118  <author initials="P." surname="Leach" fullname="Paul J. Leach">
119    <organization abbrev="Microsoft">Microsoft Corporation</organization>
120    <address>
121      <postal>
122        <street>1 Microsoft Way</street>
123        <city>Redmond</city>
124        <region>WA</region>
125        <code>98052</code>
126      </postal>
127      <email>paulle@microsoft.com</email>
128    </address>
129  </author>
130   
131  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
132    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
133    <address>
134      <postal>
135        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
136        <street>The Stata Center, Building 32</street>
137        <street>32 Vassar Street</street>
138        <city>Cambridge</city>
139        <region>MA</region>
140        <code>02139</code>
141        <country>USA</country>
142      </postal>
143      <email>timbl@w3.org</email>
144      <uri>http://www.w3.org/People/Berners-Lee/</uri>
145    </address>
146  </author>
147
148  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
149    <organization abbrev="W3C">World Wide Web Consortium</organization>
150    <address>
151      <postal>
152        <street>W3C / ERCIM</street>
153        <street>2004, rte des Lucioles</street>
154        <city>Sophia-Antipolis</city>
155        <region>AM</region>
156        <code>06902</code>
157        <country>France</country>
158      </postal>
159      <email>ylafon@w3.org</email>
160      <uri>http://www.raubacapeu.net/people/yves/</uri>
161    </address>
162  </author>
163
164  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
165    <organization abbrev="greenbytes">greenbytes GmbH</organization>
166    <address>
167      <postal>
168        <street>Hafenweg 16</street>
169        <city>Muenster</city><region>NW</region><code>48155</code>
170        <country>Germany</country>
171      </postal>
172      <phone>+49 251 2807760</phone>   
173      <facsimile>+49 251 2807761</facsimile>   
174      <email>julian.reschke@greenbytes.de</email>       
175      <uri>http://greenbytes.de/tech/webdav/</uri>     
176    </address>
177  </author>
178
179  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
180
181<abstract>
182<t>
183   The Hypertext Transfer Protocol (HTTP) is an application-level
184   protocol for distributed, collaborative, hypermedia information
185   systems. HTTP has been in use by the World Wide Web global information
186   initiative since 1990. This document is Part 5 of the seven-part specification
187   that defines the protocol referred to as "HTTP/1.1" and, taken together,
188   obsoletes RFC 2616.  Part 5 defines range-specific requests and
189   the rules for constructing and combining responses to those requests.
190</t>
191</abstract>
192
193<note title="Editorial Note (To be removed by RFC Editor)">
194  <t>
195    Discussion of this draft should take place on the HTTPBIS working group
196    mailing list (ietf-http-wg@w3.org). The current issues list is
197    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
198    and related documents (including fancy diffs) can be found at
199    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
200  </t>
201  <t>
202    The changes in this draft are summarized in <xref target="changes.since.04"/>.
203  </t>
204</note>
205</front>
206<middle>
207<section title="Introduction" anchor="introduction">
208<t>
209   HTTP clients often encounter interrupted data transfers as a result
210   of cancelled requests or dropped connections.  When a cache has stored
211   a partial representation, it is desirable to request the remainder
212   of that representation in a subsequent request rather than transfer
213   the entire representation.
214   There are also a number of Web applications that benefit from being
215   able to request only a subset of a larger representation, such as a
216   single page of a very large document or only part of an image to be
217   rendered by a device with limited local storage.
218</t>
219<t>
220   This document defines HTTP/1.1 range requests,
221   partial responses, and the multipart/byteranges media type.
222   The protocol for range requests is an &OPTIONAL; feature of HTTP,
223   designed so resources or recipients that do not implement this feature
224   can respond as if it is a normal GET request without impacting
225   interoperability.  Partial responses are indicated by a distinct status
226   code to not be mistaken for full responses by intermediate caches
227   that might not implement the feature.
228</t>
229<t>
230   Although the HTTP range request mechanism is designed to allow for
231   extensible range types, this specification only defines requests for
232   byte ranges.
233</t>
234
235<section title="Requirements" anchor="intro.requirements">
236<t>
237   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
238   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
239   document are to be interpreted as described in <xref target="RFC2119"/>.
240</t>
241<t>
242   An implementation is not compliant if it fails to satisfy one or more
243   of the &MUST; or &REQUIRED; level requirements for the protocols it
244   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
245   level and all the &SHOULD; level requirements for its protocols is said
246   to be "unconditionally compliant"; one that satisfies all the &MUST;
247   level requirements but not all the &SHOULD; level requirements for its
248   protocols is said to be "conditionally compliant."
249</t>
250</section>
251</section>
252
253<section title="Notational Conventions and Generic Grammar" anchor="notation">
254  <x:anchor-alias value="DIGIT"/>
255  <x:anchor-alias value="SP"/>
256  <x:anchor-alias value="token"/>
257  <x:anchor-alias value="BWS"/>
258  <x:anchor-alias value="OWS"/>
259  <x:anchor-alias value="RWS"/>
260<t>
261  This specification uses the ABNF syntax defined in &notation-abnf; and
262  the core rules defined in &basic-rules;:
263  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
264  <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>.</cref>
265</t>
266<figure><artwork type="abnf2616">
267  <x:ref>DIGIT</x:ref>      = &lt;DIGIT, defined in &basic-rules;&gt;
268  <x:ref>SP</x:ref>         = &lt;SP, defined in &basic-rules;&gt;
269</artwork></figure>
270<figure><artwork type="abnf2616">
271  <x:ref>token</x:ref>      = &lt;token, defined in &basic-rules;&gt;
272  <x:ref>BWS</x:ref>        = &lt;BWS, defined in &basic-rules;&gt;
273  <x:ref>OWS</x:ref>        = &lt;OWS, defined in &basic-rules;&gt;
274  <x:ref>RWS</x:ref>        = &lt;RWS, defined in &basic-rules;&gt;
275</artwork></figure>
276<t anchor="abnf.dependencies">
277  <x:anchor-alias value="entity-tag"/>
278  <x:anchor-alias value="HTTP-date"/>
279  The ABNF rules below are defined in other parts:
280</t>
281<figure><!--Part1--><artwork type="abnf2616">
282  <x:ref>HTTP-date</x:ref>  = &lt;HTTP-date, defined in &full-date;&gt;
283</artwork></figure>
284<figure><!--Part4--><artwork type="abnf2616">
285  <x:ref>entity-tag</x:ref> = &lt;entity-tag, defined in &entity-tags;&gt;
286</artwork></figure>
287</section>
288
289<section title="Range Units" anchor="range.units">
290  <x:anchor-alias value="bytes-unit"/>
291  <x:anchor-alias value="other-range-unit"/>
292  <x:anchor-alias value="range-unit"/>
293<t>
294   HTTP/1.1 allows a client to request that only part (a range of) the
295   response entity be included within the response. HTTP/1.1 uses range
296   units in the Range (<xref target="header.range"/>) and Content-Range (<xref target="header.content-range"/>)
297   header fields. An entity can be broken down into subranges according
298   to various structural units.
299</t>
300<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"/>
301  <x:ref>range-unit</x:ref>       = <x:ref>bytes-unit</x:ref> / <x:ref>other-range-unit</x:ref>
302  <x:ref>bytes-unit</x:ref>       = "bytes"
303  <x:ref>other-range-unit</x:ref> = <x:ref>token</x:ref>
304</artwork></figure>
305<t>
306   The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1
307   implementations &MAY; ignore ranges specified using other units.
308</t>
309<t>
310   HTTP/1.1 has been designed to allow implementations of applications
311   that do not depend on knowledge of ranges.
312</t>
313</section>
314
315<section title="Status Code Definitions">
316<section title="206 Partial Content" anchor="status.206">
317  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
318  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
319<t>
320   The server has fulfilled the partial GET request for the resource.
321   The request &MUST; have included a Range header field (<xref target="header.range"/>)
322   indicating the desired range, and &MAY; have included an If-Range
323   header field (<xref target="header.if-range"/>) to make the request conditional.
324</t>
325<t>
326   The response &MUST; include the following header fields:
327  <list style="symbols">
328    <t>
329        Either a Content-Range header field (<xref target="header.content-range"/>) indicating
330        the range included with this response, or a multipart/byteranges
331        Content-Type including Content-Range fields for each part. If a
332        Content-Length header field is present in the response, its
333        value &MUST; match the actual number of OCTETs transmitted in the
334        message-body.
335    </t>
336    <t>
337        Date
338    </t>
339    <t>
340        ETag and/or Content-Location, if the header would have been sent
341        in a 200 response to the same request
342    </t>
343    <t>
344        Expires, Cache-Control, and/or Vary, if the field-value might
345        differ from that sent in any previous response for the same
346        variant
347    </t>
348  </list>
349</t>
350<t>
351   If the 206 response is the result of an If-Range request, the response
352   &SHOULD-NOT; include other entity-headers. Otherwise, the response
353   &MUST; include all of the entity-headers that would have been returned
354   with a 200 (OK) response to the same request.
355</t>
356<t>
357   A cache &MUST-NOT; combine a 206 response with other previously cached
358   content if the ETag or Last-Modified headers do not match exactly,
359   see <xref target="combining.byte.ranges"/>.
360</t>
361<t>
362   A cache that does not support the Range and Content-Range headers
363   &MUST-NOT; cache 206 (Partial Content) responses.
364</t>
365</section>
366
367<section title="416 Requested Range Not Satisfiable" anchor="status.416">
368  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
369  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
370<t>
371   A server &SHOULD; return a response with this status code if a request
372   included a Range request-header field (<xref target="header.range"/>), and none of
373   the ranges-specifier values in this field overlap the current extent
374   of the selected resource, and the request did not include an If-Range
375   request-header field. (For byte-ranges, this means that the first-byte-pos
376   of all of the byte-range-spec values were greater than the
377   current length of the selected resource.)
378</t>
379<t>
380   When this status code is returned for a byte-range request, the
381   response &SHOULD; include a Content-Range entity-header field
382   specifying the current length of the selected resource (see <xref target="header.content-range"/>).
383   This response &MUST-NOT; use the multipart/byteranges content-type.
384</t>
385</section>
386</section>
387
388<section title="Combining Byte Ranges" anchor="combining.byte.ranges">
389<t>
390   A response might transfer only a subrange of the bytes of an entity-body,
391   either because the request included one or more Range
392   specifications, or because a connection was broken prematurely. After
393   several such transfers, a cache might have received several ranges of
394   the same entity-body.
395</t>
396<t>
397   If a cache has a stored non-empty set of subranges for an entity, and
398   an incoming response transfers another subrange, the cache &MAY;
399   combine the new subrange with the existing set if both the following
400   conditions are met:
401  <list style="symbols">
402    <t>Both the incoming response and the cache entry have a cache
403        validator.</t>
404    <t>The two cache validators match using the strong comparison
405        function (see &weak-and-strong-validators;).</t>
406  </list>
407</t>
408<t>
409   If either requirement is not met, the cache &MUST; use only the most
410   recent partial response (based on the Date values transmitted with
411   every response, and using the incoming response if these values are
412   equal or missing), and &MUST; discard the other partial information.
413</t>
414</section>
415
416<section title="Header Field Definitions" anchor="header.fields">
417<t>
418   This section defines the syntax and semantics of HTTP/1.1 header fields
419   related to range requests and partial responses.
420</t>
421<t>
422   For entity-header fields, both sender and recipient refer to either the
423   client or the server, depending on who sends and who receives the entity.
424</t>
425
426<section title="Accept-Ranges" anchor="header.accept-ranges">
427  <iref primary="true" item="Accept-Ranges header" x:for-anchor=""/>
428  <iref primary="true" item="Headers" subitem="Accept-Ranges" x:for-anchor=""/>
429  <x:anchor-alias value="Accept-Ranges"/>
430  <x:anchor-alias value="Accept-Ranges-v"/>
431  <x:anchor-alias value="acceptable-ranges"/>
432<t>
433      The response-header "Accept-Ranges" field allows the server to
434      indicate its acceptance of range requests for a resource:
435</t>
436<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Ranges"/><iref primary="true" item="Grammar" subitem="Accept-Ranges-v"/><iref primary="true" item="Grammar" subitem="acceptable-ranges"/>
437  <x:ref>Accept-Ranges</x:ref>     = "Accept-Ranges" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Accept-Ranges-v</x:ref>
438  <x:ref>Accept-Ranges-v</x:ref>   = <x:ref>acceptable-ranges</x:ref>
439  <x:ref>acceptable-ranges</x:ref> = 1#<x:ref>range-unit</x:ref> / "none"
440</artwork></figure>
441<t>
442      Origin servers that accept byte-range requests &MAY; send
443</t>
444<figure><artwork type="example">
445  Accept-Ranges: bytes
446</artwork></figure>
447<t>
448      but are not required to do so. Clients &MAY; generate byte-range
449      requests without having received this header for the resource
450      involved. Range units are defined in <xref target="range.units"/>.
451</t>
452<t>
453      Servers that do not accept any kind of range request for a
454      resource &MAY; send
455</t>
456<figure><artwork type="example">
457  Accept-Ranges: none
458</artwork></figure>
459<t>
460      to advise the client not to attempt a range request.
461</t>
462</section>
463
464<section title="Content-Range" anchor="header.content-range">
465  <iref primary="true" item="Content-Range header" x:for-anchor=""/>
466  <iref primary="true" item="Headers" subitem="Content-Range" x:for-anchor=""/>
467  <x:anchor-alias value="byte-content-range-spec"/>
468  <x:anchor-alias value="byte-range-resp-spec"/>
469  <x:anchor-alias value="Content-Range"/>
470  <x:anchor-alias value="Content-Range-v"/>
471  <x:anchor-alias value="content-range-spec"/>
472  <x:anchor-alias value="instance-length"/>
473<t>
474   The entity-header "Content-Range" is sent with a partial entity-body to
475   specify where in the full entity-body the partial body should be
476   applied. Range units are defined in <xref target="range.units"/>.
477</t>
478<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Range"/><iref primary="true" item="Grammar" subitem="Content-Range-v"/><iref primary="true" item="Grammar" subitem="content-range-spec"/><iref primary="true" item="Grammar" subitem="byte-content-range-spec"/><iref primary="true" item="Grammar" subitem="byte-range-resp-spec"/><iref primary="true" item="Grammar" subitem="instance-length"/>
479  <x:ref>Content-Range</x:ref> = "Content-Range" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Content-Range-v</x:ref>
480  <x:ref>Content-Range-v</x:ref> = <x:ref>content-range-spec</x:ref>
481 
482  <x:ref>content-range-spec</x:ref>      = <x:ref>byte-content-range-spec</x:ref>
483  <x:ref>byte-content-range-spec</x:ref> = <x:ref>bytes-unit</x:ref> <x:ref>SP</x:ref>
484                            <x:ref>byte-range-resp-spec</x:ref> "/"
485                            ( <x:ref>instance-length</x:ref> / "*" )
486 
487  <x:ref>byte-range-resp-spec</x:ref>    = (<x:ref>first-byte-pos</x:ref> "-" <x:ref>last-byte-pos</x:ref>)
488                          / "*"
489                         
490  <x:ref>instance-length</x:ref>         = 1*<x:ref>DIGIT</x:ref>
491</artwork></figure>
492<t>
493   The header &SHOULD; indicate the total length of the full entity-body,
494   unless this length is unknown or difficult to determine. The asterisk
495   "*" character means that the instance-length is unknown at the time
496   when the response was generated.
497</t>
498<t>
499   Unlike byte-ranges-specifier values (see <xref target="byte.ranges"/>), a byte-range-resp-spec
500   &MUST; only specify one range, and &MUST; contain
501   absolute byte positions for both the first and last byte of the
502   range.
503</t>
504<t>
505   A byte-content-range-spec with a byte-range-resp-spec whose last-byte-pos
506   value is less than its first-byte-pos value, or whose
507   instance-length value is less than or equal to its last-byte-pos
508   value, is invalid. The recipient of an invalid byte-content-range-spec
509   &MUST; ignore it and any content transferred along with it.
510</t>
511<t>
512   A server sending a response with status code 416 (Requested range not
513   satisfiable) &SHOULD; include a Content-Range field with a byte-range-resp-spec
514   of "*". The instance-length specifies the current length of
515   the selected resource. A response with status code 206 (Partial
516   Content) &MUST-NOT; include a Content-Range field with a byte-range-resp-spec of "*".
517</t>
518<t>
519   Examples of byte-content-range-spec values, assuming that the entity
520   contains a total of 1234 bytes:
521   <list style="symbols">
522      <t>
523        The first 500 bytes:
524<figure><artwork type="text/plain">
525   bytes 0-499/1234
526</artwork></figure>
527      </t>   
528      <t>
529        The second 500 bytes:
530<figure><artwork type="text/plain">
531   bytes 500-999/1234
532</artwork></figure>
533      </t>   
534      <t>
535        All except for the first 500 bytes:
536<figure><artwork type="text/plain">
537   bytes 500-1233/1234
538</artwork></figure>
539      </t>   
540      <t>
541        The last 500 bytes:
542<figure><artwork type="text/plain">
543   bytes 734-1233/1234
544</artwork></figure>
545      </t>   
546   </list>
547</t>
548<t>
549   When an HTTP message includes the content of a single range (for
550   example, a response to a request for a single range, or to a request
551   for a set of ranges that overlap without any holes), this content is
552   transmitted with a Content-Range header, and a Content-Length header
553   showing the number of bytes actually transferred. For example,
554</t>
555<figure><artwork type="example">
556  HTTP/1.1 206 Partial Content
557  Date: Wed, 15 Nov 1995 06:25:24 GMT
558  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
559  Content-Range: bytes 21010-47021/47022
560  Content-Length: 26012
561  Content-Type: image/gif
562</artwork></figure>
563<t>
564   When an HTTP message includes the content of multiple ranges (for
565   example, a response to a request for multiple non-overlapping
566   ranges), these are transmitted as a multipart message. The multipart
567   media type used for this purpose is "multipart/byteranges" as defined
568   in <xref target="internet.media.type.multipart.byteranges"/>. See <xref target="changes.from.rfc.2068"/> for a compatibility issue.
569</t>
570<t>
571   A response to a request for a single range &MUST-NOT; be sent using the
572   multipart/byteranges media type.  A response to a request for
573   multiple ranges, whose result is a single range, &MAY; be sent as a
574   multipart/byteranges media type with one part. A client that cannot
575   decode a multipart/byteranges message &MUST-NOT; ask for multiple
576   byte-ranges in a single request.
577</t>
578<t>
579   When a client requests multiple byte-ranges in one request, the
580   server &SHOULD; return them in the order that they appeared in the
581   request.
582</t>
583<t>
584   If the server ignores a byte-range-spec because it is syntactically
585   invalid, the server &SHOULD; treat the request as if the invalid Range
586   header field did not exist. (Normally, this means return a 200
587   response containing the full entity).
588</t>
589<t>
590   If the server receives a request (other than one including an If-Range
591   request-header field) with an unsatisfiable Range request-header
592   field (that is, all of whose byte-range-spec values have a
593   first-byte-pos value greater than the current length of the selected
594   resource), it &SHOULD; return a response code of 416 (Requested range
595   not satisfiable) (<xref target="status.416"/>).
596  <list><t>
597      <x:h>Note:</x:h> clients cannot depend on servers to send a 416 (Requested
598      range not satisfiable) response instead of a 200 (OK) response for
599      an unsatisfiable Range request-header, since not all servers
600      implement this request-header.
601  </t></list>
602</t>
603</section>
604
605<section title="If-Range" anchor="header.if-range">
606  <iref primary="true" item="If-Range header" x:for-anchor=""/>
607  <iref primary="true" item="Headers" subitem="If-Range" x:for-anchor=""/>
608  <x:anchor-alias value="If-Range"/>
609  <x:anchor-alias value="If-Range-v"/>
610<t>
611   If a client has a partial copy of an entity in its cache, and wishes
612   to have an up-to-date copy of the entire entity in its cache, it
613   could use the Range request-header with a conditional GET (using
614   either or both of If-Unmodified-Since and If-Match.) However, if the
615   condition fails because the entity has been modified, the client
616   would then have to make a second request to obtain the entire current
617   entity-body.
618</t>
619<t>
620   The request header "If-Range" allows a client to "short-circuit" the second
621   request. Informally, its meaning is `if the entity is unchanged, send
622   me the part(s) that I am missing; otherwise, send me the entire new
623   entity'.
624</t>
625<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-Range"/><iref primary="true" item="Grammar" subitem="If-Range-v"/>
626  <x:ref>If-Range</x:ref>   = "If-Range" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>If-Range-v</x:ref>
627  <x:ref>If-Range-v</x:ref> = <x:ref>entity-tag</x:ref> / <x:ref>HTTP-date</x:ref>
628</artwork></figure>
629<t>
630   If the client has no entity tag for an entity, but does have a Last-Modified
631   date, it &MAY; use that date in an If-Range header. (The
632   server can distinguish between a valid HTTP-date and any form of
633   entity-tag by examining no more than two characters.) The If-Range
634   header &SHOULD; only be used together with a Range header, and &MUST; be
635   ignored if the request does not include a Range header, or if the
636   server does not support the sub-range operation.
637</t>
638<t>
639   If the entity tag given in the If-Range header matches the current
640   entity tag for the entity, then the server &SHOULD; provide the
641   specified sub-range of the entity using a 206 (Partial Content)
642   response. If the entity tag does not match, then the server &SHOULD;
643   return the entire entity using a 200 (OK) response.
644</t>
645</section>
646
647<section title="Range" anchor="header.range">
648  <iref primary="true" item="Range header" x:for-anchor=""/>
649  <iref primary="true" item="Headers" subitem="Range" x:for-anchor=""/>
650
651<section title="Byte Ranges" anchor="byte.ranges">
652<t>
653   Since all HTTP entities are represented in HTTP messages as sequences
654   of bytes, the concept of a byte range is meaningful for any HTTP
655   entity. (However, not all clients and servers need to support byte-range
656   operations.)
657</t>
658<t>
659   Byte range specifications in HTTP apply to the sequence of bytes in
660   the entity-body (not necessarily the same as the message-body).
661</t>
662<t anchor="rule.ranges-specifier">
663  <x:anchor-alias value="byte-range-set"/>
664  <x:anchor-alias value="byte-range-spec"/>
665  <x:anchor-alias value="byte-ranges-specifier"/>
666  <x:anchor-alias value="first-byte-pos"/>
667  <x:anchor-alias value="last-byte-pos"/>
668  <x:anchor-alias value="ranges-specifier"/>
669  <x:anchor-alias value="suffix-byte-range-spec"/>
670  <x:anchor-alias value="suffix-length"/>
671   A byte range operation &MAY; specify a single range of bytes, or a set
672   of ranges within a single entity.
673</t>
674<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"/>
675  <x:ref>ranges-specifier</x:ref> = <x:ref>byte-ranges-specifier</x:ref>
676  <x:ref>byte-ranges-specifier</x:ref> = <x:ref>bytes-unit</x:ref> "=" <x:ref>byte-range-set</x:ref>
677  <x:ref>byte-range-set</x:ref>  = 1#( <x:ref>byte-range-spec</x:ref> / <x:ref>suffix-byte-range-spec</x:ref> )
678  <x:ref>byte-range-spec</x:ref> = <x:ref>first-byte-pos</x:ref> "-" [<x:ref>last-byte-pos</x:ref>]
679  <x:ref>first-byte-pos</x:ref>  = 1*<x:ref>DIGIT</x:ref>
680  <x:ref>last-byte-pos</x:ref>   = 1*<x:ref>DIGIT</x:ref>
681</artwork></figure>
682<t>
683   The first-byte-pos value in a byte-range-spec gives the byte-offset
684   of the first byte in a range. The last-byte-pos value gives the
685   byte-offset of the last byte in the range; that is, the byte
686   positions specified are inclusive. Byte offsets start at zero.
687</t>
688<t>
689   If the last-byte-pos value is present, it &MUST; be greater than or
690   equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec
691   is syntactically invalid. The recipient of a byte-range-set
692   that includes one or more syntactically invalid byte-range-spec
693   values &MUST; ignore the header field that includes that byte-range-set.
694</t>
695<t>
696   If the last-byte-pos value is absent, or if the value is greater than
697   or equal to the current length of the entity-body, last-byte-pos is
698   taken to be equal to one less than the current length of the entity-body
699   in bytes.
700</t>
701<t>
702   By its choice of last-byte-pos, a client can limit the number of
703   bytes retrieved without knowing the size of the entity.
704</t>
705<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="suffix-byte-range-spec"/><iref primary="true" item="Grammar" subitem="suffix-length"/>
706  <x:ref>suffix-byte-range-spec</x:ref> = "-" <x:ref>suffix-length</x:ref>
707  <x:ref>suffix-length</x:ref> = 1*<x:ref>DIGIT</x:ref>
708</artwork></figure>
709<t>
710   A suffix-byte-range-spec is used to specify the suffix of the
711   entity-body, of a length given by the suffix-length value. (That is,
712   this form specifies the last N bytes of an entity-body.) If the
713   entity is shorter than the specified suffix-length, the entire
714   entity-body is used.
715</t>
716<t>
717   If a syntactically valid byte-range-set includes at least one byte-range-spec
718   whose first-byte-pos is less than the current length of
719   the entity-body, or at least one suffix-byte-range-spec with a non-zero
720   suffix-length, then the byte-range-set is satisfiable.
721   Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set
722   is unsatisfiable, the server &SHOULD; return a response with a status
723   of 416 (Requested range not satisfiable). Otherwise, the server
724   &SHOULD; return a response with a status of 206 (Partial Content)
725   containing the satisfiable ranges of the entity-body.
726</t>
727<t>
728   Examples of byte-ranges-specifier values (assuming an entity-body of
729   length 10000):
730  <list style="symbols">
731     <t>The first 500 bytes (byte offsets 0-499, inclusive):  bytes=0-499</t>
732
733     <t>The second 500 bytes (byte offsets 500-999, inclusive):
734        bytes=500-999</t>
735
736     <t>The final 500 bytes (byte offsets 9500-9999, inclusive):
737        bytes=-500</t>
738
739     <t>Or bytes=9500-</t>
740
741     <t>The first and last bytes only (bytes 0 and 9999):  bytes=0-0,-1</t>
742
743     <t>Several legal but not canonical specifications of the second 500
744        bytes (byte offsets 500-999, inclusive):
745        <vspace/>
746         bytes=500-600,601-999<vspace/>
747         bytes=500-700,601-999</t>
748  </list>
749</t>
750</section>
751
752<section title="Range Retrieval Requests" anchor="range.retrieval.requests">
753  <x:anchor-alias value="Range"/>
754  <x:anchor-alias value="Range-v"/>
755<t>
756   HTTP retrieval requests using conditional or unconditional GET
757   methods &MAY; request one or more sub-ranges of the entity, instead of
758   the entire entity, using the Range request header, which applies to
759   the entity returned as the result of the request:
760</t>
761<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Range"/><iref primary="true" item="Grammar" subitem="Range-v"/>
762  <x:ref>Range</x:ref>   = "Range" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Range-v</x:ref>
763  <x:ref>Range-v</x:ref> = <x:ref>ranges-specifier</x:ref>
764</artwork></figure>
765<t>
766   A server &MAY; ignore the Range header. However, HTTP/1.1 origin
767   servers and intermediate caches ought to support byte ranges when
768   possible, since Range supports efficient recovery from partially
769   failed transfers, and supports efficient partial retrieval of large
770   entities.
771</t>
772<t>
773   If the server supports the Range header and the specified range or
774   ranges are appropriate for the entity:
775  <list style="symbols">
776     <t>The presence of a Range header in an unconditional GET modifies
777        what is returned if the GET is otherwise successful. In other
778        words, the response carries a status code of 206 (Partial
779        Content) instead of 200 (OK).</t>
780
781     <t>The presence of a Range header in a conditional GET (a request
782        using one or both of If-Modified-Since and If-None-Match, or
783        one or both of If-Unmodified-Since and If-Match) modifies what
784        is returned if the GET is otherwise successful and the
785        condition is true. It does not affect the 304 (Not Modified)
786        response returned if the conditional is false.</t>
787  </list>
788</t>
789<t>
790   In some cases, it might be more appropriate to use the If-Range
791   header (see <xref target="header.if-range"/>) in addition to the Range header.
792</t>
793<t>
794   If a proxy that supports ranges receives a Range request, forwards
795   the request to an inbound server, and receives an entire entity in
796   reply, it &SHOULD; only return the requested range to its client. It
797   &SHOULD; store the entire received response in its cache if that is
798   consistent with its cache allocation policies.
799</t>
800</section>
801</section>
802</section>
803
804<section title="IANA Considerations" anchor="IANA.considerations">
805<section title="Message Header Registration" anchor="message.header.registration">
806<t>
807   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
808   with the permanent registrations below (see <xref target="RFC3864"/>):
809</t>
810<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
811<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
812   <ttcol>Header Field Name</ttcol>
813   <ttcol>Protocol</ttcol>
814   <ttcol>Status</ttcol>
815   <ttcol>Reference</ttcol>
816
817   <c>Accept-Ranges</c>
818   <c>http</c>
819   <c>standard</c>
820   <c>
821      <xref target="header.accept-ranges"/>
822   </c>
823   <c>Content-Range</c>
824   <c>http</c>
825   <c>standard</c>
826   <c>
827      <xref target="header.content-range"/>
828   </c>
829   <c>If-Range</c>
830   <c>http</c>
831   <c>standard</c>
832   <c>
833      <xref target="header.if-range"/>
834   </c>
835   <c>Range</c>
836   <c>http</c>
837   <c>standard</c>
838   <c>
839      <xref target="header.range"/>
840   </c>
841</texttable>
842<!--(END)-->
843<t>
844   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
845</t>
846</section>
847</section>
848
849<section title="Security Considerations" anchor="security.considerations">
850<t>
851   No additional security considerations have been identified beyond
852   those applicable to HTTP in general &messaging;.
853</t>
854</section>
855
856<section title="Acknowledgments" anchor="ack">
857<t>
858   Most of the specification of ranges is based on work originally done
859   by Ari Luotonen and John Franks, with additional input from Steve
860   Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin Hamilton,
861   Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz, Larry Masinter,
862   Jeff Mogul, Lou Montulli, David W. Morris, Luigi Rizzo, and Bill Weihl.
863</t>
864</section>
865</middle>
866<back>
867
868<references title="Normative References">
869
870<reference anchor="Part1">
871  <front>
872    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
873    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
874      <organization abbrev="Day Software">Day Software</organization>
875      <address><email>fielding@gbiv.com</email></address>
876    </author>
877    <author initials="J." surname="Gettys" fullname="Jim Gettys">
878      <organization>One Laptop per Child</organization>
879      <address><email>jg@laptop.org</email></address>
880    </author>
881    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
882      <organization abbrev="HP">Hewlett-Packard Company</organization>
883      <address><email>JeffMogul@acm.org</email></address>
884    </author>
885    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
886      <organization abbrev="Microsoft">Microsoft Corporation</organization>
887      <address><email>henrikn@microsoft.com</email></address>
888    </author>
889    <author initials="L." surname="Masinter" fullname="Larry Masinter">
890      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
891      <address><email>LMM@acm.org</email></address>
892    </author>
893    <author initials="P." surname="Leach" fullname="Paul J. Leach">
894      <organization abbrev="Microsoft">Microsoft Corporation</organization>
895      <address><email>paulle@microsoft.com</email></address>
896    </author>
897    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
898      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
899      <address><email>timbl@w3.org</email></address>
900    </author>
901    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
902      <organization abbrev="W3C">World Wide Web Consortium</organization>
903      <address><email>ylafon@w3.org</email></address>
904    </author>
905    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
906      <organization abbrev="greenbytes">greenbytes GmbH</organization>
907      <address><email>julian.reschke@greenbytes.de</email></address>
908    </author>
909    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
910  </front>
911  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
912  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
913</reference>
914
915<reference anchor="Part3">
916  <front>
917    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
918    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
919      <organization abbrev="Day Software">Day Software</organization>
920      <address><email>fielding@gbiv.com</email></address>
921    </author>
922    <author initials="J." surname="Gettys" fullname="Jim Gettys">
923      <organization>One Laptop per Child</organization>
924      <address><email>jg@laptop.org</email></address>
925    </author>
926    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
927      <organization abbrev="HP">Hewlett-Packard Company</organization>
928      <address><email>JeffMogul@acm.org</email></address>
929    </author>
930    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
931      <organization abbrev="Microsoft">Microsoft Corporation</organization>
932      <address><email>henrikn@microsoft.com</email></address>
933    </author>
934    <author initials="L." surname="Masinter" fullname="Larry Masinter">
935      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
936      <address><email>LMM@acm.org</email></address>
937    </author>
938    <author initials="P." surname="Leach" fullname="Paul J. Leach">
939      <organization abbrev="Microsoft">Microsoft Corporation</organization>
940      <address><email>paulle@microsoft.com</email></address>
941    </author>
942    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
943      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
944      <address><email>timbl@w3.org</email></address>
945    </author>
946    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
947      <organization abbrev="W3C">World Wide Web Consortium</organization>
948      <address><email>ylafon@w3.org</email></address>
949    </author>
950    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
951      <organization abbrev="greenbytes">greenbytes GmbH</organization>
952      <address><email>julian.reschke@greenbytes.de</email></address>
953    </author>
954    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
955  </front>
956  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
957  <x:source href="p3-payload.xml" basename="p3-payload"/>
958</reference>
959
960<reference anchor="Part4">
961  <front>
962    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
963    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
964      <organization abbrev="Day Software">Day Software</organization>
965      <address><email>fielding@gbiv.com</email></address>
966    </author>
967    <author initials="J." surname="Gettys" fullname="Jim Gettys">
968      <organization>One Laptop per Child</organization>
969      <address><email>jg@laptop.org</email></address>
970    </author>
971    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
972      <organization abbrev="HP">Hewlett-Packard Company</organization>
973      <address><email>JeffMogul@acm.org</email></address>
974    </author>
975    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
976      <organization abbrev="Microsoft">Microsoft Corporation</organization>
977      <address><email>henrikn@microsoft.com</email></address>
978    </author>
979    <author initials="L." surname="Masinter" fullname="Larry Masinter">
980      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
981      <address><email>LMM@acm.org</email></address>
982    </author>
983    <author initials="P." surname="Leach" fullname="Paul J. Leach">
984      <organization abbrev="Microsoft">Microsoft Corporation</organization>
985      <address><email>paulle@microsoft.com</email></address>
986    </author>
987    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
988      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
989      <address><email>timbl@w3.org</email></address>
990    </author>
991    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
992      <organization abbrev="W3C">World Wide Web Consortium</organization>
993      <address><email>ylafon@w3.org</email></address>
994    </author>
995    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
996      <organization abbrev="greenbytes">greenbytes GmbH</organization>
997      <address><email>julian.reschke@greenbytes.de</email></address>
998    </author>
999    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1000  </front>
1001  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1002  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1003</reference>
1004
1005<reference anchor="Part6">
1006  <front>
1007    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1008    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1009      <organization abbrev="Day Software">Day Software</organization>
1010      <address><email>fielding@gbiv.com</email></address>
1011    </author>
1012    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1013      <organization>One Laptop per Child</organization>
1014      <address><email>jg@laptop.org</email></address>
1015    </author>
1016    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1017      <organization abbrev="HP">Hewlett-Packard Company</organization>
1018      <address><email>JeffMogul@acm.org</email></address>
1019    </author>
1020    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1021      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1022      <address><email>henrikn@microsoft.com</email></address>
1023    </author>
1024    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1025      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1026      <address><email>LMM@acm.org</email></address>
1027    </author>
1028    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1029      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1030      <address><email>paulle@microsoft.com</email></address>
1031    </author>
1032    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1033      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1034      <address><email>timbl@w3.org</email></address>
1035    </author>
1036    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1037      <organization abbrev="W3C">World Wide Web Consortium</organization>
1038      <address><email>ylafon@w3.org</email></address>
1039    </author>
1040    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1041      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1042      <address><email>julian.reschke@greenbytes.de</email></address>
1043    </author>
1044    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1045  </front>
1046  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
1047  <x:source href="p6-cache.xml" basename="p6-cache"/>
1048</reference>
1049
1050<reference anchor="RFC2046">
1051  <front>
1052    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1053    <author initials="N." surname="Freed" fullname="Ned Freed">
1054      <organization>Innosoft International, Inc.</organization>
1055      <address><email>ned@innosoft.com</email></address>
1056    </author>
1057    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1058      <organization>First Virtual Holdings</organization>
1059      <address><email>nsb@nsb.fv.com</email></address>
1060    </author>
1061    <date month="November" year="1996"/>
1062  </front>
1063  <seriesInfo name="RFC" value="2046"/>
1064</reference>
1065
1066<reference anchor="RFC2119">
1067  <front>
1068    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1069    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1070      <organization>Harvard University</organization>
1071      <address><email>sob@harvard.edu</email></address>
1072    </author>
1073    <date month="March" year="1997"/>
1074  </front>
1075  <seriesInfo name="BCP" value="14"/>
1076  <seriesInfo name="RFC" value="2119"/>
1077</reference>
1078
1079</references>
1080
1081<references title="Informative References">
1082
1083<reference anchor="RFC2616">
1084  <front>
1085    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
1086    <author initials="R." surname="Fielding" fullname="R. Fielding">
1087      <organization>University of California, Irvine</organization>
1088      <address><email>fielding@ics.uci.edu</email></address>
1089    </author>
1090    <author initials="J." surname="Gettys" fullname="J. Gettys">
1091      <organization>W3C</organization>
1092      <address><email>jg@w3.org</email></address>
1093    </author>
1094    <author initials="J." surname="Mogul" fullname="J. Mogul">
1095      <organization>Compaq Computer Corporation</organization>
1096      <address><email>mogul@wrl.dec.com</email></address>
1097    </author>
1098    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
1099      <organization>MIT Laboratory for Computer Science</organization>
1100      <address><email>frystyk@w3.org</email></address>
1101    </author>
1102    <author initials="L." surname="Masinter" fullname="L. Masinter">
1103      <organization>Xerox Corporation</organization>
1104      <address><email>masinter@parc.xerox.com</email></address>
1105    </author>
1106    <author initials="P." surname="Leach" fullname="P. Leach">
1107      <organization>Microsoft Corporation</organization>
1108      <address><email>paulle@microsoft.com</email></address>
1109    </author>
1110    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
1111      <organization>W3C</organization>
1112      <address><email>timbl@w3.org</email></address>
1113    </author>
1114    <date month="June" year="1999"/>
1115  </front>
1116  <seriesInfo name="RFC" value="2616"/>
1117</reference>
1118
1119<reference anchor='RFC3864'>
1120  <front>
1121    <title>Registration Procedures for Message Header Fields</title>
1122    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
1123      <organization>Nine by Nine</organization>
1124      <address><email>GK-IETF@ninebynine.org</email></address>
1125    </author>
1126    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
1127      <organization>BEA Systems</organization>
1128      <address><email>mnot@pobox.com</email></address>
1129    </author>
1130    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
1131      <organization>HP Labs</organization>
1132      <address><email>JeffMogul@acm.org</email></address>
1133    </author>
1134    <date year='2004' month='September' />
1135  </front>
1136  <seriesInfo name='BCP' value='90' />
1137  <seriesInfo name='RFC' value='3864' />
1138</reference>
1139
1140<reference anchor="RFC4288">
1141  <front>
1142    <title>Media Type Specifications and Registration Procedures</title>
1143    <author initials="N." surname="Freed" fullname="N. Freed">
1144      <organization>Sun Microsystems</organization>
1145      <address>
1146        <email>ned.freed@mrochek.com</email>
1147      </address>
1148    </author>
1149    <author initials="J." surname="Klensin" fullname="J. Klensin">
1150      <organization/>
1151      <address>
1152        <email>klensin+ietf@jck.com</email>
1153      </address>
1154    </author>
1155    <date year="2005" month="December"/>
1156  </front>
1157  <seriesInfo name="BCP" value="13"/>
1158  <seriesInfo name="RFC" value="4288"/>
1159</reference>
1160
1161</references>
1162
1163<section title="Internet Media Type multipart/byteranges" anchor="internet.media.type.multipart.byteranges">
1164<iref item="Media Type" subitem="multipart/byteranges" primary="true"/>
1165<iref item="multipart/byteranges Media Type" primary="true"/>
1166<t>
1167   When an HTTP 206 (Partial Content) response message includes the
1168   content of multiple ranges (a response to a request for multiple
1169   non-overlapping ranges), these are transmitted as a multipart
1170   message-body (<xref target="RFC2046" x:fmt="," x:sec="5.1"/>). The media type for this purpose is called
1171   "multipart/byteranges".  The following is to be registered with IANA <xref target="RFC4288"/>.
1172</t><t>
1173   The multipart/byteranges media type includes one or more parts, each
1174   with its own Content-Type and Content-Range fields. The required
1175   boundary parameter specifies the boundary string used to separate
1176   each body-part.
1177</t>
1178<t>
1179  <list style="hanging" x:indent="12em">
1180    <t hangText="Type name:">
1181      multipart
1182    </t>
1183    <t hangText="Subtype name:">
1184      byteranges
1185    </t>
1186    <t hangText="Required parameters:">
1187      boundary
1188    </t>
1189    <t hangText="Optional parameters:">
1190      none
1191    </t>
1192    <t hangText="Encoding considerations:">
1193      only "7bit", "8bit", or "binary" are permitted
1194    </t>
1195    <t hangText="Security considerations:">
1196      none
1197    </t>
1198    <t hangText="Interoperability considerations:">
1199      none
1200    </t>
1201    <t hangText="Published specification:">
1202      This specification (see <xref target="internet.media.type.multipart.byteranges"/>).
1203    </t>
1204    <t hangText="Applications that use this media type:">
1205    </t>
1206    <t hangText="Additional information:">
1207      <list style="hanging">
1208        <t hangText="Magic number(s):">none</t>
1209        <t hangText="File extension(s):">none</t>
1210        <t hangText="Macintosh file type code(s):">none</t>
1211      </list>
1212    </t>
1213    <t hangText="Person and email address to contact for further information:">
1214      See Authors Section.
1215    </t>
1216                <t hangText="Intended usage:">
1217                  COMMON
1218    </t>
1219                <t hangText="Restrictions on usage:">
1220                  none
1221    </t>
1222    <t hangText="Author/Change controller:">
1223      IESG
1224    </t>
1225  </list>
1226</t>
1227<figure><preamble>
1228   For example:
1229</preamble><artwork type="example">
1230   HTTP/1.1 206 Partial Content
1231   Date: Wed, 15 Nov 1995 06:25:24 GMT
1232   Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1233   Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1234
1235   --THIS_STRING_SEPARATES
1236   Content-type: application/pdf
1237   Content-range: bytes 500-999/8000
1238
1239   ...the first range...
1240   --THIS_STRING_SEPARATES
1241   Content-type: application/pdf
1242   Content-range: bytes 7000-7999/8000
1243
1244   ...the second range
1245   --THIS_STRING_SEPARATES--
1246</artwork></figure>
1247<t>
1248      Notes:
1249  <list style="numbers">
1250      <t>Additional CRLFs may precede the first boundary string in the
1251         entity.</t>
1252
1253      <t>Although <xref target="RFC2046"/> permits the boundary string to be
1254         quoted, some existing implementations handle a quoted boundary
1255         string incorrectly.</t>
1256
1257      <t>A number of browsers and servers were coded to an early draft
1258         of the byteranges specification to use a media type of
1259         multipart/x-byteranges<iref item="multipart/x-byteranges Media Type"/><iref item="Media Type" subitem="multipart/x-byteranges"/>, which is almost, but not quite
1260         compatible with the version documented in HTTP/1.1.</t>
1261  </list>
1262</t>
1263</section>
1264
1265<section title="Compatibility with Previous Versions" anchor="compatibility">
1266<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
1267<t>
1268   Transfer-coding and message lengths all interact in ways that
1269   required fixing exactly when chunked encoding is used (to allow for
1270   transfer encoding that may not be self delimiting); it was important
1271   to straighten out exactly how message lengths are computed.
1272   (<xref target="header.content-range"/>,
1273   see also <xref target="Part1"/>, <xref target="Part3"/> and <xref target="Part6"/>)
1274</t>
1275<t>
1276   There are situations where a server (especially a proxy) does not
1277   know the full length of a response but is capable of serving a
1278   byterange request. We therefore need a mechanism to allow byteranges
1279   with a content-range not indicating the full length of the message.
1280   (<xref target="header.content-range"/>)
1281</t>
1282<t>
1283   Range request responses would become very verbose if all meta-data
1284   were always returned; by allowing the server to only send needed
1285   headers in a 206 response, this problem can be avoided.
1286   (Section <xref target="status.206" format="counter"/>
1287   and <xref target="header.if-range" format="counter"/>)
1288</t>
1289<t>
1290   Fix problem with unsatisfiable range requests; there are two cases:
1291   syntactic problems, and range doesn't exist in the document. The 416
1292   status code was needed to resolve this ambiguity needed to indicate
1293   an error for a byte range request that falls outside of the actual
1294   contents of a document. (Section <xref target="status.416" format="counter"/>, <xref target="header.content-range" format="counter"/>)
1295</t>
1296</section>
1297
1298<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
1299<t>
1300  Clarify that it is not ok to use a weak cache validator in a 206 response.
1301  (<xref target="status.206"/>)
1302</t>
1303<t>
1304  Clarify that multipart/byteranges can consist of a single part.
1305  (<xref target="internet.media.type.multipart.byteranges"/>)
1306</t>
1307
1308</section>
1309
1310</section>
1311
1312<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
1313
1314<section title="Since RFC2616">
1315<t>
1316  Extracted relevant partitions from <xref target="RFC2616"/>.
1317</t>
1318</section>
1319
1320<section title="Since draft-ietf-httpbis-p5-range-00">
1321<t>
1322  Closed issues:
1323  <list style="symbols"> 
1324    <t>
1325      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/18"/>:
1326      "Cache validators in 206 responses"
1327      (<eref target="http://purl.org/NET/http-errata#ifrange206"/>)
1328    </t>
1329    <t>
1330      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
1331      "Normative and Informative references"
1332    </t>
1333    <t>
1334      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
1335      "Normative up-to-date references"
1336    </t>
1337  </list>
1338</t>
1339</section>
1340
1341<section title="Since draft-ietf-httpbis-p5-range-01">
1342<t>
1343  Closed issues:
1344  <list style="symbols"> 
1345    <t>
1346      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
1347      "Updating to RFC4288"
1348    </t>
1349  </list>
1350</t>
1351<t>
1352  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1353  <list style="symbols"> 
1354    <t>
1355      Add explicit references to BNF syntax and rules imported from other parts of the specification.
1356    </t>
1357  </list>
1358</t>
1359</section>
1360
1361<section title="Since draft-ietf-httpbis-p5-range-02" anchor="changes.since.02">
1362<t>
1363  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
1364  <list style="symbols"> 
1365    <t>
1366      Reference RFC 3984, and update header registrations for headers defined
1367      in this document.
1368    </t>
1369  </list>
1370</t>
1371</section>
1372
1373<section title="Since draft-ietf-httpbis-p5-range-03" anchor="changes.since.03">
1374<t>
1375</t>
1376</section>
1377
1378<section title="Since draft-ietf-httpbis-p5-range-04" anchor="changes.since.04">
1379<t>
1380  Closed issues:
1381  <list style="symbols"> 
1382    <t>
1383      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/133"/>:
1384      "multipart/byteranges minimum number of parts"
1385    </t>
1386  </list>
1387</t>
1388<t>
1389  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1390  <list style="symbols"> 
1391    <t>
1392      Use "/" instead of "|" for alternatives.
1393    </t>
1394    <t>
1395      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
1396      whitespace ("OWS") and required whitespace ("RWS").
1397    </t>
1398    <t>
1399      Rewrite ABNFs to spell out whitespace rules, factor out
1400      header value format definitions.
1401    </t>
1402  </list>
1403</t>
1404</section>
1405
1406</section>
1407
1408</back>
1409</rfc>
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