source: draft-ietf-httpbis/latest/p5-range.xml @ 1397

Last change on this file since 1397 was 1397, checked in by julian.reschke@…, 8 years ago

ABNF consistency

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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 "August">
16  <!ENTITY ID-YEAR "2011">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY acks                       "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY field-rules                "<xref target='Part1' x:rel='#field.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY entity-tags                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY weak-and-strong-validators "<xref target='Part4' x:rel='#weak.and.strong.validators' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY lastmod-comparison         "<xref target='Part4' x:rel='#lastmod.comparison' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27]>
28<?rfc toc="yes" ?>
29<?rfc symrefs="yes" ?>
30<?rfc sortrefs="yes" ?>
31<?rfc compact="yes"?>
32<?rfc subcompact="no" ?>
33<?rfc linkmailto="no" ?>
34<?rfc editing="no" ?>
35<?rfc comments="yes"?>
36<?rfc inline="yes"?>
37<?rfc rfcedstyle="yes"?>
38<?rfc-ext allow-markup-in-artwork="yes" ?>
39<?rfc-ext include-references-in-index="yes" ?>
40<rfc obsoletes="2616" category="std" x:maturity-level="draft"
41     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p5-range-&ID-VERSION;"     xmlns:x='http://purl.org/net/xml2rfc/ext'>
42<front>
43
44  <title abbrev="HTTP/1.1, Part 5">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
45
46  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
47    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
48    <address>
49      <postal>
50        <street>345 Park Ave</street>
51        <city>San Jose</city>
52        <region>CA</region>
53        <code>95110</code>
54        <country>USA</country>
55      </postal>
56      <email>fielding@gbiv.com</email>
57      <uri>http://roy.gbiv.com/</uri>
58    </address>
59  </author>
60
61  <author initials="J." surname="Gettys" fullname="Jim Gettys">
62    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
63    <address>
64      <postal>
65        <street>21 Oak Knoll Road</street>
66        <city>Carlisle</city>
67        <region>MA</region>
68        <code>01741</code>
69        <country>USA</country>
70      </postal>
71      <email>jg@freedesktop.org</email>
72      <uri>http://gettys.wordpress.com/</uri>
73    </address>
74  </author>
75 
76  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
77    <organization abbrev="HP">Hewlett-Packard Company</organization>
78    <address>
79      <postal>
80        <street>HP Labs, Large Scale Systems Group</street>
81        <street>1501 Page Mill Road, MS 1177</street>
82        <city>Palo Alto</city>
83        <region>CA</region>
84        <code>94304</code>
85        <country>USA</country>
86      </postal>
87      <email>JeffMogul@acm.org</email>
88    </address>
89  </author>
90
91  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
92    <organization abbrev="Microsoft">Microsoft Corporation</organization>
93    <address>
94      <postal>
95        <street>1 Microsoft Way</street>
96        <city>Redmond</city>
97        <region>WA</region>
98        <code>98052</code>
99        <country>USA</country>
100      </postal>
101      <email>henrikn@microsoft.com</email>
102    </address>
103  </author>
104
105  <author initials="L." surname="Masinter" fullname="Larry Masinter">
106    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
107    <address>
108      <postal>
109        <street>345 Park Ave</street>
110        <city>San Jose</city>
111        <region>CA</region>
112        <code>95110</code>
113        <country>USA</country>
114      </postal>
115      <email>LMM@acm.org</email>
116      <uri>http://larry.masinter.net/</uri>
117    </address>
118  </author>
119 
120  <author initials="P." surname="Leach" fullname="Paul J. Leach">
121    <organization abbrev="Microsoft">Microsoft Corporation</organization>
122    <address>
123      <postal>
124        <street>1 Microsoft Way</street>
125        <city>Redmond</city>
126        <region>WA</region>
127        <code>98052</code>
128      </postal>
129      <email>paulle@microsoft.com</email>
130    </address>
131  </author>
132   
133  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
134    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
135    <address>
136      <postal>
137        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
138        <street>The Stata Center, Building 32</street>
139        <street>32 Vassar Street</street>
140        <city>Cambridge</city>
141        <region>MA</region>
142        <code>02139</code>
143        <country>USA</country>
144      </postal>
145      <email>timbl@w3.org</email>
146      <uri>http://www.w3.org/People/Berners-Lee/</uri>
147    </address>
148  </author>
149
150  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
151    <organization abbrev="W3C">World Wide Web Consortium</organization>
152    <address>
153      <postal>
154        <street>W3C / ERCIM</street>
155        <street>2004, rte des Lucioles</street>
156        <city>Sophia-Antipolis</city>
157        <region>AM</region>
158        <code>06902</code>
159        <country>France</country>
160      </postal>
161      <email>ylafon@w3.org</email>
162      <uri>http://www.raubacapeu.net/people/yves/</uri>
163    </address>
164  </author>
165
166  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
167    <organization abbrev="greenbytes">greenbytes GmbH</organization>
168    <address>
169      <postal>
170        <street>Hafenweg 16</street>
171        <city>Muenster</city><region>NW</region><code>48155</code>
172        <country>Germany</country>
173      </postal>
174      <phone>+49 251 2807760</phone>
175      <facsimile>+49 251 2807761</facsimile>
176      <email>julian.reschke@greenbytes.de</email>
177      <uri>http://greenbytes.de/tech/webdav/</uri>
178    </address>
179  </author>
180
181  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
182  <workgroup>HTTPbis Working Group</workgroup>
183
184<abstract>
185<t>
186   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
187   distributed, collaborative, hypertext information systems. HTTP has been in
188   use by the World Wide Web global information initiative since 1990. This
189   document is Part 5 of the seven-part specification that defines the protocol
190   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
191</t>
192<t>
193   Part 5 defines range-specific requests and the rules for constructing and
194   combining responses to those requests.
195</t>
196</abstract>
197
198<note title="Editorial Note (To be removed by RFC Editor)">
199  <t>
200    Discussion of this draft should take place on the HTTPBIS working group
201    mailing list (ietf-http-wg@w3.org), which is archived at
202    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
203  </t>
204  <t>
205    The current issues list is at
206    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
207    documents (including fancy diffs) can be found at
208    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
209  </t>
210  <t>
211    The changes in this draft are summarized in <xref target="changes.since.15"/>.
212  </t>
213</note>
214</front>
215<middle>
216<section title="Introduction" anchor="introduction">
217<t>
218   HTTP clients often encounter interrupted data transfers as a result
219   of cancelled requests or dropped connections.  When a client has stored
220   a partial representation, it is desirable to request the remainder
221   of that representation in a subsequent request rather than transfer
222   the entire representation.
223   There are also a number of Web applications that benefit from being
224   able to request only a subset of a larger representation, such as a
225   single page of a very large document or only part of an image to be
226   rendered by a device with limited local storage.
227</t>
228<t>
229   This document defines HTTP/1.1 range requests,
230   partial responses, and the multipart/byteranges media type.
231   The protocol for range requests is an &OPTIONAL; feature of HTTP,
232   designed so resources or recipients that do not implement this feature
233   can respond as if it is a normal GET request without impacting
234   interoperability.  Partial responses are indicated by a distinct status
235   code to not be mistaken for full responses by intermediate caches
236   that might not implement the feature.
237</t>
238<t>
239   Although the HTTP range request mechanism is designed to allow for
240   extensible range types, this specification only defines requests for
241   byte ranges.
242</t>
243
244<section title="Requirements" anchor="intro.requirements">
245<t>
246   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
247   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
248   document are to be interpreted as described in <xref target="RFC2119"/>.
249</t>
250<t>
251   An implementation is not compliant if it fails to satisfy one or more
252   of the "MUST" or "REQUIRED" level requirements for the protocols it
253   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
254   level and all the "SHOULD" level requirements for its protocols is said
255   to be "unconditionally compliant"; one that satisfies all the "MUST"
256   level requirements but not all the "SHOULD" level requirements for its
257   protocols is said to be "conditionally compliant".
258</t>
259</section>
260
261<section title="Syntax Notation" anchor="notation">
262  <x:anchor-alias value="ALPHA"/>
263  <x:anchor-alias value="CHAR"/>
264  <x:anchor-alias value="CR"/>
265  <x:anchor-alias value="DIGIT"/>
266  <x:anchor-alias value="LF"/>
267  <x:anchor-alias value="OCTET"/>
268  <x:anchor-alias value="SP"/>
269  <x:anchor-alias value="VCHAR"/>
270  <x:anchor-alias value="WSP"/>
271<t>
272  This specification uses the ABNF syntax defined in &notation; (which
273  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
274  <xref target="collected.abnf"/> shows the collected ABNF, with the list
275  rule expanded.
276</t>
277<t>
278  The following core rules are included by
279  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
280  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
281  DIGIT (decimal 0-9), DQUOTE (double quote),
282  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
283  OCTET (any 8-bit sequence of data), SP (space),
284  VCHAR (any visible USASCII character),
285  and WSP (whitespace).
286</t>
287
288<section title="Core Rules" anchor="core.rules">
289  <x:anchor-alias value="token"/>
290  <x:anchor-alias value="OWS"/>
291  <x:anchor-alias value="HTTP-date"/>
292<t>
293  The core rules below are defined in <xref target="Part1"/>:
294</t>
295<figure><artwork type="abnf2616">
296  <x:ref>OWS</x:ref>        = &lt;OWS, defined in &basic-rules;&gt;
297  <x:ref>token</x:ref>      = &lt;token, defined in &field-rules;&gt;
298  <x:ref>HTTP-date</x:ref>  = &lt;HTTP-date, defined in &full-date;&gt;
299</artwork></figure>
300</section>
301
302<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
303  <x:anchor-alias value="entity-tag"/>
304<t>
305  The ABNF rules below are defined in other parts:
306</t>
307<figure><!--Part4--><artwork type="abnf2616">
308  <x:ref>entity-tag</x:ref> = &lt;entity-tag, defined in &entity-tags;&gt;
309</artwork></figure>
310</section>
311
312</section>
313
314</section>
315
316
317<section title="Range Units" anchor="range.units">
318  <x:anchor-alias value="bytes-unit"/>
319  <x:anchor-alias value="other-range-unit"/>
320  <x:anchor-alias value="range-unit"/>
321<t>
322   HTTP/1.1 allows a client to request that only part (a range) of the
323   representation be included within the response. HTTP/1.1 uses range
324   units in the Range (<xref target="header.range"/>) and Content-Range (<xref target="header.content-range"/>)
325   header fields. A representation can be broken down into subranges according
326   to various structural units.
327</t>
328<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"/>
329  <x:ref>range-unit</x:ref>       = <x:ref>bytes-unit</x:ref> / <x:ref>other-range-unit</x:ref>
330  <x:ref>bytes-unit</x:ref>       = "bytes"
331  <x:ref>other-range-unit</x:ref> = <x:ref>token</x:ref>
332</artwork></figure>
333<t>
334  HTTP/1.1 has been designed to allow implementations of applications
335  that do not depend on knowledge of ranges. The only range unit defined
336  by HTTP/1.1 is "bytes". Additional specifiers can be defined as described
337  in <xref target="range.specifier.registry"/>.
338</t>
339<t>
340  If a range unit is not understood in a request, a server &MUST; ignore
341  the whole Range header field (<xref target="header.range"/>).
342  If a range unit is not understood in a response, an intermediary
343  &SHOULD; pass the response to the client; a client &MUST; fail.
344</t>
345
346<section title="Range Specifier Registry" anchor="range.specifier.registry">
347<t>
348   The HTTP Range Specifier Registry defines the name space for the range
349   specifier names.
350</t>
351<t>
352   Registrations &MUST; include the following fields:
353   <list style="symbols">
354     <t>Name</t>
355     <t>Description</t>
356     <t>Pointer to specification text</t>
357   </list>
358</t>
359<t>
360  Values to be added to this name space are subject to IETF review
361  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
362</t>
363<t>
364   The registry itself is maintained at
365   <eref target="http://www.iana.org/assignments/http-range-specifiers"/>.
366</t>
367</section>
368
369</section>
370
371<section title="Status Code Definitions" anchor="status.code.definitions">
372<section title="206 Partial Content" anchor="status.206">
373  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
374  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
375<t>
376   The server has fulfilled the partial GET request for the resource.
377   The request &MUST; have included a Range header field (<xref target="header.range"/>)
378   indicating the desired range, and &MAY; have included an If-Range
379   header field (<xref target="header.if-range"/>) to make the request conditional.
380</t>
381<t>
382   The response &MUST; include the following header fields:
383  <list style="symbols">
384    <t>
385        Either a Content-Range header field (<xref target="header.content-range"/>) indicating
386        the range included with this response, or a multipart/byteranges
387        Content-Type including Content-Range fields for each part. If a
388        Content-Length header field is present in the response, its
389        value &MUST; match the actual number of octets transmitted in the
390        message-body.
391    </t>
392    <t>
393        Date
394    </t>
395    <t>
396        Cache-Control, ETag, Expires, Content-Location, Last-Modified,
397        and/or Vary, if the header field would have been sent in a 200
398        response to the same request
399    </t>
400  </list>
401</t>
402<t>
403   If the 206 response is the result of an If-Range request, the response
404   &SHOULD-NOT; include other representation header fields. Otherwise, the response
405   &MUST; include all of the representation header fields that would have been returned
406   with a 200 (OK) response to the same request.
407</t>
408</section>
409
410<section title="416 Requested Range Not Satisfiable" anchor="status.416">
411  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
412  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
413<t>
414   A server &SHOULD; return a response with this status code if a request
415   included a Range header field (<xref target="header.range"/>), and none of
416   the ranges-specifier values in this field overlap the current extent
417   of the selected resource, and the request did not include an If-Range
418   header field (<xref target="header.if-range"/>). (For byte-ranges,
419   this means that the first-byte-pos of all of the byte-range-spec values were
420   greater than the current length of the selected resource.)
421</t>
422<t>
423   When this status code is returned for a byte-range request, the
424   response &SHOULD; include a Content-Range header field
425   specifying the current length of the representation (see <xref target="header.content-range"/>).
426   This response &MUST-NOT; use the multipart/byteranges content-type.
427</t>
428</section>
429</section>
430
431<section title="Combining Ranges" anchor="combining.byte.ranges">
432<t>
433   A response might transfer only a subrange of a representation if the
434   connection closed prematurely or if the request used one or more Range
435   specifications.  After several such transfers, a client might have
436   received several ranges of the same representation.  These ranges can only
437   be safely combined if they all have in common the same strong validator,
438   where "strong validator" is defined to be either an entity-tag that is
439   not marked as weak (&entity-tags;) or, if no entity-tag is provided, a
440   Last-Modified value that is strong in the sense defined by
441   &lastmod-comparison;.
442</t>
443<t>
444   When a client receives an incomplete 200 (OK) or 206 (Partial Content)
445   response and already has one or more stored responses for the same method
446   and effective request URI, all of the stored responses with the same
447   strong validator &MAY; be combined with the partial content in this new
448   response.  If none of the stored responses contain the same strong
449   validator, then this new response corresponds to a new representation
450   and &MUST-NOT; be combined with the existing stored responses.
451</t>
452<t>
453   If the new response is an incomplete 200 (OK) response, then the header
454   fields of that new response are used for any combined response and replace
455   those of the matching stored responses.
456</t>
457<t>
458   If the new response is a 206 (Partial Content) response and at least one
459   of the matching stored responses is a 200 (OK), then the combined response
460   header fields consist of the most recent 200 response's header fields.
461   If all of the matching stored responses are 206 responses, then the
462   stored response with the most header fields is used as the source of
463   header fields for the combined response, except that the client &MUST;
464   use other header fields provided in the new response, aside from
465   Content-Range, to replace all instances of the corresponding header
466   fields in the stored response.
467</t>
468<t>
469   The combined response message-body consists of the union of partial
470   content ranges in the new response and each of the selected responses.
471   If the union consists of the entire range of the representation, then the
472   combined response &MUST; be recorded as a complete 200 (OK) response
473   with a Content-Length header field that reflects the complete length.
474   Otherwise, the combined response(s) &MUST; include a Content-Range
475   header field describing the included range(s) and be recorded as
476   incomplete.  If the union consists of a discontinuous range of the
477   representation, then the client &MAY; store it as either a multipart range
478   response or as multiple 206 responses with one continuous range each.
479</t>
480</section>
481
482<section title="Header Field Definitions" anchor="header.fields">
483<t>
484   This section defines the syntax and semantics of HTTP/1.1 header fields
485   related to range requests and partial responses.
486</t>
487
488<section title="Accept-Ranges" anchor="header.accept-ranges">
489  <iref primary="true" item="Accept-Ranges header field" x:for-anchor=""/>
490  <iref primary="true" item="Header Fields" subitem="Accept-Ranges" x:for-anchor=""/>
491  <x:anchor-alias value="Accept-Ranges"/>
492  <x:anchor-alias value="acceptable-ranges"/>
493<t>
494   The "Accept-Ranges" header field allows a resource to indicate
495   its acceptance of range requests.
496</t>
497<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Ranges"/><iref primary="true" item="Grammar" subitem="acceptable-ranges"/>
498  <x:ref>Accept-Ranges</x:ref>     = <x:ref>acceptable-ranges</x:ref>
499  <x:ref>acceptable-ranges</x:ref> = 1#<x:ref>range-unit</x:ref> / "none"
500</artwork></figure>
501<t>
502      Origin servers that accept byte-range requests &MAY; send
503</t>
504<figure><artwork type="example">
505  Accept-Ranges: bytes
506</artwork></figure>
507<t>
508      but are not required to do so. Clients &MAY; generate range
509      requests without having received this header field for the resource
510      involved. Range units are defined in <xref target="range.units"/>.
511</t>
512<t>
513      Servers that do not accept any kind of range request for a
514      resource &MAY; send
515</t>
516<figure><artwork type="example">
517  Accept-Ranges: none
518</artwork></figure>
519<t>
520      to advise the client not to attempt a range request.
521</t>
522</section>
523
524<section title="Content-Range" anchor="header.content-range">
525  <iref primary="true" item="Content-Range header field" x:for-anchor=""/>
526  <iref primary="true" item="Header Fields" subitem="Content-Range" x:for-anchor=""/>
527  <x:anchor-alias value="byte-content-range-spec"/>
528  <x:anchor-alias value="byte-range-resp-spec"/>
529  <x:anchor-alias value="Content-Range"/>
530  <x:anchor-alias value="content-range-spec"/>
531  <x:anchor-alias value="instance-length"/>
532  <x:anchor-alias value="other-content-range-spec"/>
533  <x:anchor-alias value="other-range-resp-spec"/>
534<t>
535   The "Content-Range" header field is sent with a partial representation to
536   specify where in the full representation the payload body is intended to be
537   applied.
538</t>
539<t>   
540   Range units are defined in <xref target="range.units"/>.
541</t>
542<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"/>
543  <x:ref>Content-Range</x:ref> = <x:ref>content-range-spec</x:ref>
544 
545  <x:ref>content-range-spec</x:ref>      = <x:ref>byte-content-range-spec</x:ref>
546                          / <x:ref>other-content-range-spec</x:ref>
547  <x:ref>byte-content-range-spec</x:ref> = <x:ref>bytes-unit</x:ref> <x:ref>SP</x:ref>
548                            <x:ref>byte-range-resp-spec</x:ref> "/"
549                            ( <x:ref>instance-length</x:ref> / "*" )
550 
551  <x:ref>byte-range-resp-spec</x:ref>    = (<x:ref>first-byte-pos</x:ref> "-" <x:ref>last-byte-pos</x:ref>)
552                          / "*"
553                         
554  <x:ref>instance-length</x:ref>         = 1*<x:ref>DIGIT</x:ref>
555 
556  <x:ref>other-content-range-spec</x:ref> = <x:ref>other-range-unit</x:ref> <x:ref>SP</x:ref>
557                             <x:ref>other-range-resp-spec</x:ref>
558  <x:ref>other-range-resp-spec</x:ref>    = *<x:ref>CHAR</x:ref>
559</artwork></figure>
560<t>
561   The header field &SHOULD; indicate the total length of the full representation,
562   unless this length is unknown or difficult to determine. The asterisk
563   "*" character means that the instance-length is unknown at the time
564   when the response was generated.
565</t>
566<t>
567   Unlike byte-ranges-specifier values (see <xref target="byte.ranges"/>), a byte-range-resp-spec
568   &MUST; only specify one range, and &MUST; contain
569   absolute byte positions for both the first and last byte of the
570   range.
571</t>
572<t>
573   A byte-content-range-spec with a byte-range-resp-spec whose last-byte-pos
574   value is less than its first-byte-pos value, or whose
575   instance-length value is less than or equal to its last-byte-pos
576   value, is invalid. The recipient of an invalid byte-content-range-spec
577   &MUST; ignore it and any content transferred along with it.
578</t>
579<t>
580   In the case of a byte range request:
581   A server sending a response with status code 416 (Requested range not
582   satisfiable) &SHOULD; include a Content-Range field with a byte-range-resp-spec
583   of "*". The instance-length specifies the current length of
584   the selected resource. A response with status code 206 (Partial
585   Content) &MUST-NOT; include a Content-Range field with a byte-range-resp-spec of "*".
586</t>
587<t>
588   Examples of byte-content-range-spec values, assuming that the representation
589   contains a total of 1234 bytes:
590   <list style="symbols">
591      <t>
592        The first 500 bytes:
593<figure><artwork type="example" x:indent-with="   ">
594  bytes 0-499/1234
595</artwork></figure>
596      </t>   
597      <t>
598        The second 500 bytes:
599<figure><artwork type="example" x:indent-with="   ">
600  bytes 500-999/1234
601</artwork></figure>
602      </t>   
603      <t>
604        All except for the first 500 bytes:
605<figure><artwork type="example" x:indent-with="   ">
606  bytes 500-1233/1234
607</artwork></figure>
608      </t>   
609      <t>
610        The last 500 bytes:
611<figure><artwork type="example" x:indent-with="   ">
612  bytes 734-1233/1234
613</artwork></figure>
614      </t>   
615   </list>
616</t>
617<t>
618   When an HTTP message includes the content of a single range (for
619   example, a response to a request for a single range, or to a request
620   for a set of ranges that overlap without any holes), this content is
621   transmitted with a Content-Range header field, and a Content-Length header
622   field showing the number of bytes actually transferred. For example,
623</t>
624<figure><artwork type="example">
625  HTTP/1.1 206 Partial Content
626  Date: Wed, 15 Nov 1995 06:25:24 GMT
627  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
628  Content-Range: bytes 21010-47021/47022
629  Content-Length: 26012
630  Content-Type: image/gif
631</artwork></figure>
632<t>
633   When an HTTP message includes the content of multiple ranges (for
634   example, a response to a request for multiple non-overlapping
635   ranges), these are transmitted as a multipart message. The multipart
636   media type used for this purpose is "multipart/byteranges" as defined
637   in <xref target="internet.media.type.multipart.byteranges"/>.
638</t>
639<t>
640   A response to a request for a single range &MUST-NOT; be sent using the
641   multipart/byteranges media type.  A response to a request for
642   multiple ranges, whose result is a single range, &MAY; be sent as a
643   multipart/byteranges media type with one part. A client that cannot
644   decode a multipart/byteranges message &MUST-NOT; ask for multiple
645   ranges in a single request.
646</t>
647<t>
648   When a client requests multiple ranges in one request, the
649   server &SHOULD; return them in the order that they appeared in the
650   request.
651</t>
652<t>
653   If the server ignores a byte-range-spec because it is syntactically
654   invalid, the server &SHOULD; treat the request as if the invalid Range
655   header field did not exist. (Normally, this means return a 200
656   response containing the full representation).
657</t>
658<t>
659   If the server receives a request (other than one including an If-Range
660   header field) with an unsatisfiable Range header
661   field (that is, all of whose byte-range-spec values have a
662   first-byte-pos value greater than the current length of the selected
663   resource), it &SHOULD; return a response code of 416 (Requested range
664   not satisfiable) (<xref target="status.416"/>).
665</t>
666<x:note>
667  <t>
668    <x:h>Note:</x:h> Clients cannot depend on servers to send a 416 (Requested
669    range not satisfiable) response instead of a 200 (OK) response for
670    an unsatisfiable Range header field, since not all servers
671    implement this header field.
672  </t>
673</x:note>
674</section>
675
676<section title="If-Range" anchor="header.if-range">
677  <iref primary="true" item="If-Range header field" x:for-anchor=""/>
678  <iref primary="true" item="Header Fields" subitem="If-Range" x:for-anchor=""/>
679  <x:anchor-alias value="If-Range"/>
680<t>
681   If a client has a partial copy of a representation and wishes
682   to have an up-to-date copy of the entire representation, it
683   could use the Range header field with a conditional GET (using
684   either or both of If-Unmodified-Since and If-Match.) However, if the
685   condition fails because the representation has been modified, the client
686   would then have to make a second request to obtain the entire current
687   representation.
688</t>
689<t>
690   The "If-Range" header field allows a client to "short-circuit" the second
691   request. Informally, its meaning is "if the representation is unchanged, send
692   me the part(s) that I am missing; otherwise, send me the entire new
693   representation".
694</t>
695<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-Range"/>
696  <x:ref>If-Range</x:ref> = <x:ref>entity-tag</x:ref> / <x:ref>HTTP-date</x:ref>
697</artwork></figure>
698<t>
699   Clients &MUST-NOT; use an entity-tag marked as weak in an If-Range
700   field value and &MUST-NOT; use a Last-Modified date in an If-Range
701   field value unless it has no entity-tag for the representation and
702   the Last-Modified date it does have for the representation is strong
703   in the sense defined by &lastmod-comparison;.
704</t>
705<t>
706   A server that evaluates a conditional range request that is applicable
707   to one of its representations &MUST; evaluate the condition as false if
708   the entity-tag used as a validator is marked as weak or, when an HTTP-date
709   is used as the validator, if the date value is not strong in the sense
710   defined by &lastmod-comparison;. (A server can distinguish between a
711   valid HTTP-date and any form of entity-tag by examining the first
712   two characters.)
713</t>
714<t>
715   The If-Range header field &SHOULD; only be sent by clients together with
716   a Range header field.  The If-Range header field &MUST; be ignored if it
717   is received in a request that does not include a Range header field.
718   The If-Range header field &MUST; be ignored by a server that does not
719   support the sub-range operation.
720</t>
721<t>
722   If the validator given in the If-Range header field matches the current
723   validator for the selected representation of the target resource, then
724   the server &SHOULD; send the specified sub-range of the representation
725   using a 206 (Partial Content) response. If the validator does not match,
726   then the server &SHOULD; send the entire representation using a 200 (OK)
727   response.
728</t>
729</section>
730
731<section title="Range" anchor="header.range">
732  <iref primary="true" item="Range header field" x:for-anchor=""/>
733  <iref primary="true" item="Header Fields" subitem="Range" x:for-anchor=""/>
734
735<section title="Byte Ranges" anchor="byte.ranges">
736<t>
737   Since all HTTP representations are transferred as sequences
738   of bytes, the concept of a byte range is meaningful for any HTTP
739   representation. (However, not all clients and servers need to support byte-range
740   operations.)
741</t>
742<t>
743   Byte range specifications in HTTP apply to the sequence of bytes in
744   the representation body (not necessarily the same as the message-body).
745</t>
746<t anchor="rule.ranges-specifier">
747  <x:anchor-alias value="byte-range-set"/>
748  <x:anchor-alias value="byte-range-spec"/>
749  <x:anchor-alias value="byte-ranges-specifier"/>
750  <x:anchor-alias value="first-byte-pos"/>
751  <x:anchor-alias value="last-byte-pos"/>
752  <x:anchor-alias value="ranges-specifier"/>
753  <x:anchor-alias value="suffix-byte-range-spec"/>
754  <x:anchor-alias value="suffix-length"/>
755
756   A byte range operation &MAY; specify a single range of bytes, or a set
757   of ranges within a single representation.
758</t>
759<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"/>
760  <x:ref>byte-ranges-specifier</x:ref> = <x:ref>bytes-unit</x:ref> "=" <x:ref>byte-range-set</x:ref>
761  <x:ref>byte-range-set</x:ref>  = 1#( <x:ref>byte-range-spec</x:ref> / <x:ref>suffix-byte-range-spec</x:ref> )
762  <x:ref>byte-range-spec</x:ref> = <x:ref>first-byte-pos</x:ref> "-" [ <x:ref>last-byte-pos</x:ref> ]
763  <x:ref>first-byte-pos</x:ref>  = 1*<x:ref>DIGIT</x:ref>
764  <x:ref>last-byte-pos</x:ref>   = 1*<x:ref>DIGIT</x:ref>
765</artwork></figure>
766<t>
767   The first-byte-pos value in a byte-range-spec gives the byte-offset
768   of the first byte in a range. The last-byte-pos value gives the
769   byte-offset of the last byte in the range; that is, the byte
770   positions specified are inclusive. Byte offsets start at zero.
771</t>
772<t>
773   If the last-byte-pos value is present, it &MUST; be greater than or
774   equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec
775   is syntactically invalid. The recipient of a byte-range-set
776   that includes one or more syntactically invalid byte-range-spec
777   values &MUST; ignore the header field that includes that byte-range-set.
778</t>
779<t>
780   If the last-byte-pos value is absent, or if the value is greater than
781   or equal to the current length of the representation body, last-byte-pos is
782   taken to be equal to one less than the current length of the representation
783   in bytes.
784</t>
785<t>
786   By its choice of last-byte-pos, a client can limit the number of
787   bytes retrieved without knowing the size of the representation.
788</t>
789<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="suffix-byte-range-spec"/><iref primary="true" item="Grammar" subitem="suffix-length"/>
790  <x:ref>suffix-byte-range-spec</x:ref> = "-" <x:ref>suffix-length</x:ref>
791  <x:ref>suffix-length</x:ref> = 1*<x:ref>DIGIT</x:ref>
792</artwork></figure>
793<t>
794   A suffix-byte-range-spec is used to specify the suffix of the
795   representation body, of a length given by the suffix-length value. (That is,
796   this form specifies the last N bytes of a representation.) If the
797   representation is shorter than the specified suffix-length, the entire
798   representation is used.
799</t>
800<t>
801   If a syntactically valid byte-range-set includes at least one byte-range-spec
802   whose first-byte-pos is less than the current length of
803   the representation, or at least one suffix-byte-range-spec with a non-zero
804   suffix-length, then the byte-range-set is satisfiable.
805   Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set
806   is unsatisfiable, the server &SHOULD; return a response with a
807   416 (Requested range not satisfiable) status code. Otherwise, the server
808   &SHOULD; return a response with a 206 (Partial Content) status code
809   containing the satisfiable ranges of the representation.
810</t>
811<t>
812   Examples of byte-ranges-specifier values (assuming a representation of
813   length 10000):
814  <list style="symbols">
815     <t>The first 500 bytes (byte offsets 0-499, inclusive):
816<figure><artwork type="example" x:indent-with="   ">
817  bytes=0-499
818</artwork></figure>
819    </t>
820     <t>The second 500 bytes (byte offsets 500-999, inclusive):
821<figure><artwork type="example" x:indent-with="   ">
822  bytes=500-999
823</artwork></figure>
824    </t>
825     <t>The final 500 bytes (byte offsets 9500-9999, inclusive):
826<figure><artwork type="example" x:indent-with="   ">
827  bytes=-500
828</artwork></figure>
829    Or:
830<figure><artwork type="example" x:indent-with="   ">
831  bytes=9500-
832</artwork></figure>
833    </t>
834     <t>The first and last bytes only (bytes 0 and 9999):
835<figure><artwork type="example" x:indent-with="   ">
836  bytes=0-0,-1
837</artwork></figure>
838     </t>
839     <t>Several legal but not canonical specifications of the second 500
840        bytes (byte offsets 500-999, inclusive):
841<figure><artwork type="example" x:indent-with="   ">
842  bytes=500-600,601-999
843  bytes=500-700,601-999
844</artwork></figure>
845     </t>
846  </list>
847</t>
848</section>
849
850<section title="Range Retrieval Requests" anchor="range.retrieval.requests">
851  <x:anchor-alias value="Range"/>
852  <x:anchor-alias value="other-ranges-specifier"/>
853  <x:anchor-alias value="other-range-set"/>
854<t>
855   The "Range" header field defines the GET method (conditional or
856   not) to request one or more sub-ranges of the response representation body, instead
857   of the entire representation body.
858</t>
859<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Range"/>
860  <x:ref>Range</x:ref> = <x:ref>byte-ranges-specifier</x:ref> / <x:ref>other-ranges-specifier</x:ref>
861  <x:ref>other-ranges-specifier</x:ref> = <x:ref>other-range-unit</x:ref> "=" <x:ref>other-range-set</x:ref>
862  <x:ref>other-range-set</x:ref> = 1*<x:ref>CHAR</x:ref>
863</artwork></figure>
864<t>
865   A server &MAY; ignore the Range header field. However, origin
866   servers and intermediate caches ought to support byte ranges when
867   possible, since Range supports efficient recovery from partially
868   failed transfers, and supports efficient partial retrieval of large
869   representations.
870</t>
871<t>
872   If the server supports the Range header field and the specified range or
873   ranges are appropriate for the representation:
874  <list style="symbols">
875     <t>The presence of a Range header field in an unconditional GET modifies
876        what is returned if the GET is otherwise successful. In other
877        words, the response carries a status code of 206 (Partial
878        Content) instead of 200 (OK).</t>
879
880     <t>The presence of a Range header field in a conditional GET (a request
881        using one or both of If-Modified-Since and If-None-Match, or
882        one or both of If-Unmodified-Since and If-Match) modifies what
883        is returned if the GET is otherwise successful and the
884        condition is true. It does not affect the 304 (Not Modified)
885        response returned if the conditional is false.</t>
886  </list>
887</t>
888<t>
889   In some cases, it might be more appropriate to use the If-Range
890   header field (see <xref target="header.if-range"/>) in addition to the Range
891   header field.
892</t>
893<t>
894   If a proxy that supports ranges receives a Range request, forwards
895   the request to an inbound server, and receives an entire representation in
896   reply, it &MAY; only return the requested range to its client.
897</t>
898</section>
899</section>
900</section>
901
902<section title="IANA Considerations" anchor="IANA.considerations">
903
904<section title="Status Code Registration" anchor="status.code.registration">
905<t>
906   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
907   shall be updated with the registrations below:
908</t>
909<?BEGININC p5-range.iana-status-codes ?>
910<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
911<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
912   <ttcol>Value</ttcol>
913   <ttcol>Description</ttcol>
914   <ttcol>Reference</ttcol>
915   <c>206</c>
916   <c>Partial Content</c>
917   <c>
918      <xref target="status.206"/>
919   </c>
920   <c>416</c>
921   <c>Requested Range Not Satisfiable</c>
922   <c>
923      <xref target="status.416"/>
924   </c>
925</texttable>
926<!--(END)-->
927<?ENDINC p5-range.iana-status-codes ?>
928</section>
929
930<section title="Header Field Registration" anchor="header.field.registration">
931<t>
932   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
933   with the permanent registrations below (see <xref target="RFC3864"/>):
934</t>
935<?BEGININC p5-range.iana-headers ?>
936<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
937<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
938   <ttcol>Header Field Name</ttcol>
939   <ttcol>Protocol</ttcol>
940   <ttcol>Status</ttcol>
941   <ttcol>Reference</ttcol>
942
943   <c>Accept-Ranges</c>
944   <c>http</c>
945   <c>standard</c>
946   <c>
947      <xref target="header.accept-ranges"/>
948   </c>
949   <c>Content-Range</c>
950   <c>http</c>
951   <c>standard</c>
952   <c>
953      <xref target="header.content-range"/>
954   </c>
955   <c>If-Range</c>
956   <c>http</c>
957   <c>standard</c>
958   <c>
959      <xref target="header.if-range"/>
960   </c>
961   <c>Range</c>
962   <c>http</c>
963   <c>standard</c>
964   <c>
965      <xref target="header.range"/>
966   </c>
967</texttable>
968<!--(END)-->
969<?ENDINC p5-range.iana-headers ?>
970<t>
971   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
972</t>
973</section>
974
975<section title="Range Specifier Registration" anchor="range.specifier.registration">
976<t>
977  The registration procedure for HTTP Range Specifiers is defined by
978  <xref target="range.specifier.registry"/> of this document.
979</t>
980<t>
981   The HTTP Range Specifier Registry shall be created at <eref target="http://www.iana.org/assignments/http-range-specifiers"/>
982   and be populated with the registrations below:
983</t>
984<texttable align="left" suppress-title="true" anchor="iana.range.specifiers.table">
985   <ttcol>Range Specifier Name</ttcol>
986   <ttcol>Description</ttcol>
987   <ttcol>Reference</ttcol>
988
989   <c>bytes</c>
990   <c>a range of octets</c>
991   <c>(this specification)</c>
992</texttable>
993<t>
994   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
995</t>
996</section>
997</section>
998
999<section title="Security Considerations" anchor="security.considerations">
1000<t>
1001   This section is meant to inform application developers, information
1002   providers, and users of the security limitations in HTTP/1.1 as
1003   described by this document. The discussion does not include
1004   definitive solutions to the problems revealed, though it does make
1005   some suggestions for reducing security risks.
1006</t>
1007<section title="Overlapping Ranges" anchor="overlapping.ranges">
1008<t>
1009   Range requests containing overlapping ranges may lead to the situation
1010   where a server is sending far more data than the size of the complete
1011   resource representation.
1012</t>
1013</section>
1014</section>
1015
1016<section title="Acknowledgments" anchor="acks">
1017<t>
1018  See &acks;.
1019</t>
1020</section>
1021</middle>
1022<back>
1023
1024<references title="Normative References">
1025
1026<reference anchor="Part1">
1027  <front>
1028    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1029    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1030      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1031      <address><email>fielding@gbiv.com</email></address>
1032    </author>
1033    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1034      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1035      <address><email>jg@freedesktop.org</email></address>
1036    </author>
1037    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1038      <organization abbrev="HP">Hewlett-Packard Company</organization>
1039      <address><email>JeffMogul@acm.org</email></address>
1040    </author>
1041    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1042      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1043      <address><email>henrikn@microsoft.com</email></address>
1044    </author>
1045    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1046      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1047      <address><email>LMM@acm.org</email></address>
1048    </author>
1049    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1050      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1051      <address><email>paulle@microsoft.com</email></address>
1052    </author>
1053    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1054      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1055      <address><email>timbl@w3.org</email></address>
1056    </author>
1057    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1058      <organization abbrev="W3C">World Wide Web Consortium</organization>
1059      <address><email>ylafon@w3.org</email></address>
1060    </author>
1061    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1062      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1063      <address><email>julian.reschke@greenbytes.de</email></address>
1064    </author>
1065    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1066  </front>
1067  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1068  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1069</reference>
1070
1071<reference anchor="Part4">
1072  <front>
1073    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1074    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1075      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1076      <address><email>fielding@gbiv.com</email></address>
1077    </author>
1078    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1079      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1080      <address><email>jg@freedesktop.org</email></address>
1081    </author>
1082    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1083      <organization abbrev="HP">Hewlett-Packard Company</organization>
1084      <address><email>JeffMogul@acm.org</email></address>
1085    </author>
1086    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1087      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1088      <address><email>henrikn@microsoft.com</email></address>
1089    </author>
1090    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1091      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
1092      <address><email>LMM@acm.org</email></address>
1093    </author>
1094    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1095      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1096      <address><email>paulle@microsoft.com</email></address>
1097    </author>
1098    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1099      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1100      <address><email>timbl@w3.org</email></address>
1101    </author>
1102    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1103      <organization abbrev="W3C">World Wide Web Consortium</organization>
1104      <address><email>ylafon@w3.org</email></address>
1105    </author>
1106    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1107      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1108      <address><email>julian.reschke@greenbytes.de</email></address>
1109    </author>
1110    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1111  </front>
1112  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1113  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1114</reference>
1115
1116<reference anchor="RFC2046">
1117  <front>
1118    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1119    <author initials="N." surname="Freed" fullname="Ned Freed">
1120      <organization>Innosoft International, Inc.</organization>
1121      <address><email>ned@innosoft.com</email></address>
1122    </author>
1123    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1124      <organization>First Virtual Holdings</organization>
1125      <address><email>nsb@nsb.fv.com</email></address>
1126    </author>
1127    <date month="November" year="1996"/>
1128  </front>
1129  <seriesInfo name="RFC" value="2046"/>
1130</reference>
1131
1132<reference anchor="RFC2119">
1133  <front>
1134    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1135    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1136      <organization>Harvard University</organization>
1137      <address><email>sob@harvard.edu</email></address>
1138    </author>
1139    <date month="March" year="1997"/>
1140  </front>
1141  <seriesInfo name="BCP" value="14"/>
1142  <seriesInfo name="RFC" value="2119"/>
1143</reference>
1144
1145<reference anchor="RFC5234">
1146  <front>
1147    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
1148    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
1149      <organization>Brandenburg InternetWorking</organization>
1150      <address>
1151        <email>dcrocker@bbiw.net</email>
1152      </address> 
1153    </author>
1154    <author initials="P." surname="Overell" fullname="Paul Overell">
1155      <organization>THUS plc.</organization>
1156      <address>
1157        <email>paul.overell@thus.net</email>
1158      </address>
1159    </author>
1160    <date month="January" year="2008"/>
1161  </front>
1162  <seriesInfo name="STD" value="68"/>
1163  <seriesInfo name="RFC" value="5234"/>
1164</reference>
1165
1166</references>
1167
1168<references title="Informative References">
1169
1170<reference anchor="RFC2616">
1171  <front>
1172    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
1173    <author initials="R." surname="Fielding" fullname="R. Fielding">
1174      <organization>University of California, Irvine</organization>
1175      <address><email>fielding@ics.uci.edu</email></address>
1176    </author>
1177    <author initials="J." surname="Gettys" fullname="J. Gettys">
1178      <organization>W3C</organization>
1179      <address><email>jg@w3.org</email></address>
1180    </author>
1181    <author initials="J." surname="Mogul" fullname="J. Mogul">
1182      <organization>Compaq Computer Corporation</organization>
1183      <address><email>mogul@wrl.dec.com</email></address>
1184    </author>
1185    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
1186      <organization>MIT Laboratory for Computer Science</organization>
1187      <address><email>frystyk@w3.org</email></address>
1188    </author>
1189    <author initials="L." surname="Masinter" fullname="L. Masinter">
1190      <organization>Xerox Corporation</organization>
1191      <address><email>masinter@parc.xerox.com</email></address>
1192    </author>
1193    <author initials="P." surname="Leach" fullname="P. Leach">
1194      <organization>Microsoft Corporation</organization>
1195      <address><email>paulle@microsoft.com</email></address>
1196    </author>
1197    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
1198      <organization>W3C</organization>
1199      <address><email>timbl@w3.org</email></address>
1200    </author>
1201    <date month="June" year="1999"/>
1202  </front>
1203  <seriesInfo name="RFC" value="2616"/>
1204</reference>
1205
1206<reference anchor='RFC3864'>
1207  <front>
1208    <title>Registration Procedures for Message Header Fields</title>
1209    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
1210      <organization>Nine by Nine</organization>
1211      <address><email>GK-IETF@ninebynine.org</email></address>
1212    </author>
1213    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
1214      <organization>BEA Systems</organization>
1215      <address><email>mnot@pobox.com</email></address>
1216    </author>
1217    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
1218      <organization>HP Labs</organization>
1219      <address><email>JeffMogul@acm.org</email></address>
1220    </author>
1221    <date year='2004' month='September' />
1222  </front>
1223  <seriesInfo name='BCP' value='90' />
1224  <seriesInfo name='RFC' value='3864' />
1225</reference>
1226
1227<reference anchor="RFC4288">
1228  <front>
1229    <title>Media Type Specifications and Registration Procedures</title>
1230    <author initials="N." surname="Freed" fullname="N. Freed">
1231      <organization>Sun Microsystems</organization>
1232      <address>
1233        <email>ned.freed@mrochek.com</email>
1234      </address>
1235    </author>
1236    <author initials="J." surname="Klensin" fullname="J. Klensin">
1237      <address>
1238        <email>klensin+ietf@jck.com</email>
1239      </address>
1240    </author>
1241    <date year="2005" month="December"/>
1242  </front>
1243  <seriesInfo name="BCP" value="13"/>
1244  <seriesInfo name="RFC" value="4288"/>
1245</reference>
1246
1247<reference anchor='RFC5226'>
1248  <front>
1249    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
1250    <author initials='T.' surname='Narten' fullname='T. Narten'>
1251      <organization>IBM</organization>
1252      <address><email>narten@us.ibm.com</email></address>
1253    </author>
1254    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
1255      <organization>Google</organization>
1256      <address><email>Harald@Alvestrand.no</email></address>
1257    </author>
1258    <date year='2008' month='May' />
1259  </front>
1260  <seriesInfo name='BCP' value='26' />
1261  <seriesInfo name='RFC' value='5226' />
1262</reference>
1263
1264</references>
1265
1266<section title="Internet Media Type multipart/byteranges" anchor="internet.media.type.multipart.byteranges">
1267<iref item="Media Type" subitem="multipart/byteranges" primary="true"/>
1268<iref item="multipart/byteranges Media Type" primary="true"/>
1269<t>
1270   When an HTTP 206 (Partial Content) response message includes the
1271   content of multiple ranges (a response to a request for multiple
1272   non-overlapping ranges), these are transmitted as a multipart
1273   message-body (<xref target="RFC2046" x:fmt="," x:sec="5.1"/>). The media type for this purpose is called
1274   "multipart/byteranges".  The following is to be registered with IANA <xref target="RFC4288"/>.
1275</t>
1276<x:note>
1277  <t>
1278    <x:h>Note:</x:h> Despite the name "multipart/byteranges" is not limited to the byte ranges only.
1279  </t>
1280</x:note>
1281<t>
1282   The multipart/byteranges media type includes one or more parts, each
1283   with its own Content-Type and Content-Range fields. The required
1284   boundary parameter specifies the boundary string used to separate
1285   each body-part.
1286</t>
1287<t>
1288  <list style="hanging" x:indent="12em">
1289    <t hangText="Type name:">
1290      multipart
1291    </t>
1292    <t hangText="Subtype name:">
1293      byteranges
1294    </t>
1295    <t hangText="Required parameters:">
1296      boundary
1297    </t>
1298    <t hangText="Optional parameters:">
1299      none
1300    </t>
1301    <t hangText="Encoding considerations:">
1302      only "7bit", "8bit", or "binary" are permitted
1303    </t>
1304    <t hangText="Security considerations:">
1305      none
1306    </t>
1307    <t hangText="Interoperability considerations:">
1308      none
1309    </t>
1310    <t hangText="Published specification:">
1311      This specification (see <xref target="internet.media.type.multipart.byteranges"/>).
1312    </t>
1313    <t hangText="Applications that use this media type:">
1314    </t>
1315    <t hangText="Additional information:">
1316      <list style="hanging">
1317        <t hangText="Magic number(s):">none</t>
1318        <t hangText="File extension(s):">none</t>
1319        <t hangText="Macintosh file type code(s):">none</t>
1320      </list>
1321    </t>
1322    <t hangText="Person and email address to contact for further information:">
1323      See Authors Section.
1324    </t>
1325    <t hangText="Intended usage:">
1326      COMMON
1327    </t>
1328    <t hangText="Restrictions on usage:">
1329      none
1330    </t>
1331    <t hangText="Author/Change controller:">
1332      IESG
1333    </t>
1334  </list>
1335</t>
1336<figure><preamble>
1337   For example:
1338</preamble><artwork type="example">
1339  HTTP/1.1 206 Partial Content
1340  Date: Wed, 15 Nov 1995 06:25:24 GMT
1341  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1342  Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1343 
1344  --THIS_STRING_SEPARATES
1345  Content-type: application/pdf
1346  Content-range: bytes 500-999/8000
1347 
1348  ...the first range...
1349  --THIS_STRING_SEPARATES
1350  Content-type: application/pdf
1351  Content-range: bytes 7000-7999/8000
1352 
1353  ...the second range
1354  --THIS_STRING_SEPARATES--
1355</artwork></figure>
1356<figure><preamble>
1357   Other example:
1358</preamble>
1359<artwork type="example">
1360  HTTP/1.1 206 Partial Content
1361  Date: Tue, 14 Nov 1995 06:25:24 GMT
1362  Last-Modified: Tue, 14 July 04:58:08 GMT
1363  Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1364 
1365  --THIS_STRING_SEPARATES
1366  Content-type: video/example
1367  Content-range: exampleunit 1.2-4.3/25
1368 
1369  ...the first range...
1370  --THIS_STRING_SEPARATES
1371  Content-type: video/example
1372  Content-range: exampleunit 11.2-14.3/25
1373 
1374  ...the second range
1375  --THIS_STRING_SEPARATES--
1376</artwork>
1377</figure>
1378<t>
1379      Notes:
1380  <list style="numbers">
1381      <t>Additional CRLFs &MAY; precede the first boundary string in the body.</t>
1382
1383      <t>Although <xref target="RFC2046"/> permits the boundary string to be
1384         quoted, some existing implementations handle a quoted boundary
1385         string incorrectly.</t>
1386
1387      <t>A number of browsers and servers were coded to an early draft
1388         of the byteranges specification to use a media type of
1389         multipart/x-byteranges<iref item="multipart/x-byteranges Media Type"/><iref item="Media Type" subitem="multipart/x-byteranges"/>, which is almost, but not quite
1390         compatible with the version documented in HTTP/1.1.</t>
1391  </list>
1392</t>
1393</section>
1394
1395<section title="Compatibility with Previous Versions" anchor="compatibility">
1396<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
1397<t>
1398  Clarify that it is not ok to use a weak validator in a 206 response.
1399  (<xref target="status.206"/>)
1400</t>
1401<t>
1402  Change ABNF productions for header fields to only define the field value.
1403  (<xref target="header.fields"/>)
1404</t>
1405<t>
1406  Clarify that multipart/byteranges can consist of a single part.
1407  (<xref target="internet.media.type.multipart.byteranges"/>)
1408</t>
1409</section>
1410
1411</section>
1412
1413<?BEGININC p5-range.abnf-appendix ?>
1414<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
1415<figure>
1416<artwork type="abnf" name="p5-range.parsed-abnf">
1417<x:ref>Accept-Ranges</x:ref> = acceptable-ranges
1418
1419<x:ref>Content-Range</x:ref> = content-range-spec
1420
1421<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
1422
1423<x:ref>If-Range</x:ref> = entity-tag / HTTP-date
1424
1425<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
1426
1427<x:ref>Range</x:ref> = byte-ranges-specifier / other-ranges-specifier
1428
1429<x:ref>acceptable-ranges</x:ref> = ( *( "," OWS ) range-unit *( OWS "," [ OWS
1430 range-unit ] ) ) / "none"
1431
1432<x:ref>byte-content-range-spec</x:ref> = bytes-unit SP byte-range-resp-spec "/" (
1433 instance-length / "*" )
1434<x:ref>byte-range-resp-spec</x:ref> = ( first-byte-pos "-" last-byte-pos ) / "*"
1435<x:ref>byte-range-set</x:ref> = ( *( "," OWS ) byte-range-spec ) / (
1436 suffix-byte-range-spec *( OWS "," [ ( OWS byte-range-spec ) /
1437 suffix-byte-range-spec ] ) )
1438<x:ref>byte-range-spec</x:ref> = first-byte-pos "-" [ last-byte-pos ]
1439<x:ref>byte-ranges-specifier</x:ref> = bytes-unit "=" byte-range-set
1440<x:ref>bytes-unit</x:ref> = "bytes"
1441
1442<x:ref>content-range-spec</x:ref> = byte-content-range-spec /
1443 other-content-range-spec
1444
1445<x:ref>entity-tag</x:ref> = &lt;entity-tag, defined in [Part4], Section 2.3&gt;
1446
1447<x:ref>first-byte-pos</x:ref> = 1*DIGIT
1448
1449<x:ref>instance-length</x:ref> = 1*DIGIT
1450
1451<x:ref>last-byte-pos</x:ref> = 1*DIGIT
1452
1453<x:ref>other-content-range-spec</x:ref> = other-range-unit SP other-range-resp-spec
1454<x:ref>other-range-resp-spec</x:ref> = *CHAR
1455<x:ref>other-range-set</x:ref> = 1*CHAR
1456<x:ref>other-range-unit</x:ref> = token
1457<x:ref>other-ranges-specifier</x:ref> = other-range-unit "=" other-range-set
1458
1459<x:ref>range-unit</x:ref> = bytes-unit / other-range-unit
1460
1461<x:ref>suffix-byte-range-spec</x:ref> = "-" suffix-length
1462<x:ref>suffix-length</x:ref> = 1*DIGIT
1463
1464<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
1465</artwork>
1466</figure>
1467<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
1468; Accept-Ranges defined but not used
1469; Content-Range defined but not used
1470; If-Range defined but not used
1471; Range defined but not used
1472</artwork></figure></section>
1473<?ENDINC p5-range.abnf-appendix ?>
1474
1475
1476<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
1477
1478<section title="Since RFC 2616">
1479<t>
1480  Extracted relevant partitions from <xref target="RFC2616"/>.
1481</t>
1482</section>
1483
1484<section title="Since draft-ietf-httpbis-p5-range-00">
1485<t>
1486  Closed issues:
1487  <list style="symbols"> 
1488    <t>
1489      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/18"/>:
1490      "Cache validators in 206 responses"
1491      (<eref target="http://purl.org/NET/http-errata#ifrange206"/>)
1492    </t>
1493    <t>
1494      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
1495      "Normative and Informative references"
1496    </t>
1497    <t>
1498      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/86"/>:
1499      "Normative up-to-date references"
1500    </t>
1501  </list>
1502</t>
1503</section>
1504
1505<section title="Since draft-ietf-httpbis-p5-range-01">
1506<t>
1507  Closed issues:
1508  <list style="symbols"> 
1509    <t>
1510      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/55"/>:
1511      "Updating to RFC4288"
1512    </t>
1513  </list>
1514</t>
1515<t>
1516  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1517  <list style="symbols"> 
1518    <t>
1519      Add explicit references to BNF syntax and rules imported from other parts of the specification.
1520    </t>
1521  </list>
1522</t>
1523</section>
1524
1525<section title="Since draft-ietf-httpbis-p5-range-02" anchor="changes.since.02">
1526<t>
1527  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
1528  <list style="symbols"> 
1529    <t>
1530      Reference RFC 3984, and update header field registrations for headers defined
1531      in this document.
1532    </t>
1533  </list>
1534</t>
1535</section>
1536
1537<section title="Since draft-ietf-httpbis-p5-range-03" anchor="changes.since.03">
1538<t>
1539  None.
1540</t>
1541</section>
1542
1543<section title="Since draft-ietf-httpbis-p5-range-04" anchor="changes.since.04">
1544<t>
1545  Closed issues:
1546  <list style="symbols"> 
1547    <t>
1548      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/133"/>:
1549      "multipart/byteranges minimum number of parts"
1550    </t>
1551  </list>
1552</t>
1553<t>
1554  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1555  <list style="symbols"> 
1556    <t>
1557      Use "/" instead of "|" for alternatives.
1558    </t>
1559    <t>
1560      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
1561      whitespace ("OWS") and required whitespace ("RWS").
1562    </t>
1563    <t>
1564      Rewrite ABNFs to spell out whitespace rules, factor out
1565      header field value format definitions.
1566    </t>
1567  </list>
1568</t>
1569</section>
1570
1571<section title="Since draft-ietf-httpbis-p5-range-05" anchor="changes.since.05">
1572<t>
1573  Closed issues:
1574  <list style="symbols"> 
1575    <t>
1576      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/142"/>:
1577      "State base for *-byte-pos and suffix-length"
1578    </t>
1579  </list>
1580</t>
1581<t>
1582  Ongoing work on Custom Ranges (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/85"/>):
1583  <list style="symbols"> 
1584    <t>
1585      Remove bias in favor of byte ranges; allow custom ranges in ABNF.
1586    </t>
1587  </list>
1588</t>
1589<t>
1590  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
1591  <list style="symbols"> 
1592    <t>
1593      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
1594    </t>
1595  </list>
1596</t>
1597</section>
1598
1599<section title="Since draft-ietf-httpbis-p5-range-06" anchor="changes.since.06">
1600<t>
1601  Closed issues:
1602  <list style="symbols"> 
1603    <t>
1604      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/161"/>:
1605      "base for numeric protocol elements"
1606    </t>
1607  </list>
1608</t>
1609</section>
1610
1611<section title="Since draft-ietf-httpbis-p5-range-07" anchor="changes.since.07">
1612<t>
1613  Closed issues:
1614  <list style="symbols">
1615    <t>
1616      Fixed discrepancy in the If-Range definition about allowed validators.
1617    </t>
1618    <t>
1619      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/150" />: "multipart/byteranges for custom range units"
1620    </t>
1621    <t>
1622      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/151" />: "range unit missing from other-ranges-specifier in Range header"
1623    </t>
1624    <t>
1625      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
1626      "move IANA registrations for optional status codes"
1627    </t>
1628  </list>
1629</t>
1630</section>
1631
1632<section title="Since draft-ietf-httpbis-p5-range-08" anchor="changes.since.08">
1633<t>
1634  No significant changes.
1635</t>
1636</section>
1637
1638<section title="Since draft-ietf-httpbis-p5-range-09" anchor="changes.since.09">
1639<t>
1640 No significant changes.
1641</t>
1642</section>
1643
1644<section title="Since draft-ietf-httpbis-p5-range-10" anchor="changes.since.10">
1645<t>
1646  Closed issues:
1647  <list style="symbols"> 
1648    <t>
1649      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
1650      "Clarify 'Requested Variant'"
1651    </t>
1652    <t>
1653      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
1654      "Clarify entity / representation / variant terminology"
1655    </t>
1656    <t>
1657      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
1658      "consider removing the 'changes from 2068' sections"
1659    </t>
1660  </list>
1661</t>
1662<t>
1663  Ongoing work on Custom Ranges (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/85"/>):
1664  <list style="symbols"> 
1665    <t>
1666      Add IANA registry.
1667    </t>
1668  </list>
1669</t>
1670</section>
1671
1672<section title="Since draft-ietf-httpbis-p5-range-11" anchor="changes.since.11">
1673<t>
1674  Closed issues:
1675  <list style="symbols"> 
1676    <t>
1677      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/217"/>:
1678      "Caches can't be required to serve ranges"
1679    </t>
1680  </list>
1681</t>
1682</section>
1683
1684<section title="Since draft-ietf-httpbis-p5-range-12" anchor="changes.since.12">
1685<t>
1686  Closed issues:
1687  <list style="symbols"> 
1688    <t>
1689      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
1690      "Header Classification"
1691    </t>
1692  </list>
1693</t>
1694</section>
1695
1696<section title="Since draft-ietf-httpbis-p5-range-13" anchor="changes.since.13">
1697<t>
1698  Closed issues:
1699  <list style="symbols">
1700    <t>
1701      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
1702      "untangle ABNFs for header fields"
1703    </t>
1704  </list>
1705</t>
1706</section>
1707
1708<section title="Since draft-ietf-httpbis-p5-range-14" anchor="changes.since.14">
1709<t>
1710  None.
1711</t>
1712</section>
1713
1714<section title="Since draft-ietf-httpbis-p5-range-15" anchor="changes.since.15">
1715<t>
1716  Closed issues:
1717  <list style="symbols">
1718    <t>
1719      <eref target="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/175"/>:
1720      "Security consideration: range flooding"
1721    </t>
1722  </list>
1723</t>
1724</section>
1725
1726</section>
1727
1728</back>
1729</rfc>
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