source: draft-ietf-httpbis/latest/p5-range.html @ 2143

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(editorial) move status codes to where they are used; no text changes

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469</style><link rel="Contents" href="#rfc.toc">
470      <link rel="Author" href="#rfc.authors">
471      <link rel="Copyright" href="#rfc.copyrightnotice">
472      <link rel="Index" href="#rfc.index">
473      <link rel="Chapter" title="1 Introduction" href="#rfc.section.1">
474      <link rel="Chapter" title="2 Range Units" href="#rfc.section.2">
475      <link rel="Chapter" title="3 Range Requests" href="#rfc.section.3">
476      <link rel="Chapter" title="4 Responses to a Range Request" href="#rfc.section.4">
477      <link rel="Chapter" title="5 IANA Considerations" href="#rfc.section.5">
478      <link rel="Chapter" title="6 Security Considerations" href="#rfc.section.6">
479      <link rel="Chapter" title="7 Acknowledgments" href="#rfc.section.7">
480      <link rel="Chapter" href="#rfc.section.8" title="8 References">
481      <link rel="Appendix" title="A Internet Media Type multipart/byteranges" href="#rfc.section.A">
482      <link rel="Appendix" title="B Changes from RFC 2616" href="#rfc.section.B">
483      <link rel="Appendix" title="C Imported ABNF" href="#rfc.section.C">
484      <link rel="Appendix" title="D Collected ABNF" href="#rfc.section.D">
485      <link rel="Appendix" title="E Change Log (to be removed by RFC Editor before publication)" href="#rfc.section.E">
486      <link href="p4-conditional.html" rel="prev">
487      <link href="p6-cache.html" rel="next">
488      <meta name="generator" content=", Revision 1.589, 2012-11-30 14:23:31, XSLT vendor: SAXON 8.9 from Saxonica">
489      <link rel="schema.dct" href="">
490      <meta name="dct.creator" content="Fielding, R.">
491      <meta name="dct.creator" content="Lafon, Y.">
492      <meta name="dct.creator" content="Reschke, J. F.">
493      <meta name="dct.identifier" content="urn:ietf:id:draft-ietf-httpbis-p5-range-latest">
494      <meta name="dct.issued" scheme="ISO8601" content="2013-01-20">
495      <meta name="dct.replaces" content="urn:ietf:rfc:2616">
496      <meta name="dct.abstract" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypertext information systems. This document defines range requests and the rules for constructing and combining responses to those requests.">
497      <meta name="description" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypertext information systems. This document defines range requests and the rules for constructing and combining responses to those requests.">
498   </head>
499   <body onload="init();">
500      <table class="header">
501         <tbody>
502            <tr>
503               <td class="left">HTTPbis Working Group</td>
504               <td class="right">R. Fielding, Editor</td>
505            </tr>
506            <tr>
507               <td class="left">Internet-Draft</td>
508               <td class="right">Adobe</td>
509            </tr>
510            <tr>
511               <td class="left">Obsoletes: <a href="">2616</a> (if approved)
512               </td>
513               <td class="right">Y. Lafon, Editor</td>
514            </tr>
515            <tr>
516               <td class="left">Intended status: Standards Track</td>
517               <td class="right">W3C</td>
518            </tr>
519            <tr>
520               <td class="left">Expires: July 24, 2013</td>
521               <td class="right">J. Reschke, Editor</td>
522            </tr>
523            <tr>
524               <td class="left"></td>
525               <td class="right">greenbytes</td>
526            </tr>
527            <tr>
528               <td class="left"></td>
529               <td class="right">January 20, 2013</td>
530            </tr>
531         </tbody>
532      </table>
533      <p class="title">Hypertext Transfer Protocol (HTTP/1.1): Range Requests<br><span class="filename">draft-ietf-httpbis-p5-range-latest</span></p>
534      <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
535      <p>The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypertext information
536         systems. This document defines range requests and the rules for constructing and combining responses to those requests.
537      </p>
538      <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor)</a></h1>
539      <p>Discussion of this draft takes place on the HTTPBIS working group mailing list (, which is archived at &lt;<a href=""></a>&gt;.
540      </p> 
541      <p>The current issues list is at &lt;<a href=""></a>&gt; and related documents (including fancy diffs) can be found at &lt;<a href=""></a>&gt;.
542      </p> 
543      <p>The changes in this draft are summarized in <a href="#changes.since.21" title="Since draft-ietf-httpbis-p5-range-21">Appendix&nbsp;E.3</a>.
544      </p>
545      <h1><a id="rfc.status" href="#rfc.status">Status of This Memo</a></h1>
546      <p>This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.</p>
547      <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute
548         working documents as Internet-Drafts. The list of current Internet-Drafts is at <a href=""></a>.
549      </p>
550      <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
551         documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
552         in progress”.
553      </p>
554      <p>This Internet-Draft will expire on July 24, 2013.</p>
555      <h1><a id="rfc.copyrightnotice" href="#rfc.copyrightnotice">Copyright Notice</a></h1>
556      <p>Copyright © 2013 IETF Trust and the persons identified as the document authors. All rights reserved.</p>
557      <p>This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (<a href=""></a>) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights
558         and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License
559         text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified
560         BSD License.
561      </p>
562      <p>This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November
563         10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to
564         allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s)
565         controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative
566         works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate
567         it into languages other than English.
568      </p>
569      <hr class="noprint">
570      <h1 class="np" id="rfc.toc"><a href="#rfc.toc">Table of Contents</a></h1>
571      <ul class="toc">
572         <li><a href="#rfc.section.1">1.</a>&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a><ul>
573               <li><a href="#rfc.section.1.1">1.1</a>&nbsp;&nbsp;&nbsp;<a href="#conformance">Conformance and Error Handling</a></li>
574               <li><a href="#rfc.section.1.2">1.2</a>&nbsp;&nbsp;&nbsp;<a href="#notation">Syntax Notation</a></li>
575            </ul>
576         </li>
577         <li><a href="#rfc.section.2">2.</a>&nbsp;&nbsp;&nbsp;<a href="#range.units">Range Units</a><ul>
578               <li><a href="#rfc.section.2.1">2.1</a>&nbsp;&nbsp;&nbsp;<a href="#byte.ranges">Byte Ranges</a></li>
579               <li><a href="#rfc.section.2.2">2.2</a>&nbsp;&nbsp;&nbsp;<a href="#range.units.other">Other Range Units</a></li>
580               <li><a href="#rfc.section.2.3">2.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.accept-ranges">Accept-Ranges</a></li>
581            </ul>
582         </li>
583         <li><a href="#rfc.section.3">3.</a>&nbsp;&nbsp;&nbsp;<a href="#range.requests">Range Requests</a><ul>
584               <li><a href="#rfc.section.3.1">3.1</a>&nbsp;&nbsp;&nbsp;<a href="#header.range">Range</a></li>
585               <li><a href="#rfc.section.3.2">3.2</a>&nbsp;&nbsp;&nbsp;<a href="#header.if-range">If-Range</a></li>
586            </ul>
587         </li>
588         <li><a href="#rfc.section.4">4.</a>&nbsp;&nbsp;&nbsp;<a href="#range.response">Responses to a Range Request</a><ul>
589               <li><a href="#rfc.section.4.1">4.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.4.1">Response to a Single and Multiple Ranges Request</a></li>
590               <li><a href="#rfc.section.4.2">4.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.206">206 Partial Content</a></li>
591               <li><a href="#rfc.section.4.3">4.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.416">416 Range Not Satisfiable</a></li>
592               <li><a href="#rfc.section.4.4">4.4</a>&nbsp;&nbsp;&nbsp;<a href="#header.content-range">Content-Range</a></li>
593               <li><a href="#rfc.section.4.5">4.5</a>&nbsp;&nbsp;&nbsp;<a href="#combining.byte.ranges">Combining Ranges</a></li>
594            </ul>
595         </li>
596         <li><a href="#rfc.section.5">5.</a>&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a><ul>
597               <li><a href="#rfc.section.5.1">5.1</a>&nbsp;&nbsp;&nbsp;<a href="#range.unit.registry">Range Unit Registry</a><ul>
598                     <li><a href="#rfc.section.5.1.1">5.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#range.unit.registry.procedure">Procedure</a></li>
599                     <li><a href="#rfc.section.5.1.2">5.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#range.unit.registration">Registrations</a></li>
600                  </ul>
601               </li>
602               <li><a href="#rfc.section.5.2">5.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.registration">Status Code Registration</a></li>
603               <li><a href="#rfc.section.5.3">5.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.field.registration">Header Field Registration</a></li>
604            </ul>
605         </li>
606         <li><a href="#rfc.section.6">6.</a>&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul>
607               <li><a href="#rfc.section.6.1">6.1</a>&nbsp;&nbsp;&nbsp;<a href="#overlapping.ranges">Overlapping Ranges</a></li>
608            </ul>
609         </li>
610         <li><a href="#rfc.section.7">7.</a>&nbsp;&nbsp;&nbsp;<a href="#acks">Acknowledgments</a></li>
611         <li><a href="#rfc.section.8">8.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
612               <li><a href="#rfc.section.8.1">8.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
613               <li><a href="#rfc.section.8.2">8.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
614            </ul>
615         </li>
616         <li><a href="#rfc.authors">Authors' Addresses</a></li>
617         <li><a href="#rfc.section.A">A.</a>&nbsp;&nbsp;&nbsp;<a href="">Internet Media Type multipart/byteranges</a></li>
618         <li><a href="#rfc.section.B">B.</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></li>
619         <li><a href="#rfc.section.C">C.</a>&nbsp;&nbsp;&nbsp;<a href="#imported.abnf">Imported ABNF</a></li>
620         <li><a href="#rfc.section.D">D.</a>&nbsp;&nbsp;&nbsp;<a href="#collected.abnf">Collected ABNF</a></li>
621         <li><a href="#rfc.section.E">E.</a>&nbsp;&nbsp;&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a><ul>
622               <li><a href="#rfc.section.E.1">E.1</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.19">Since draft-ietf-httpbis-p5-range-19</a></li>
623               <li><a href="#rfc.section.E.2">E.2</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.20">Since draft-ietf-httpbis-p5-range-20</a></li>
624               <li><a href="#rfc.section.E.3">E.3</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.21">Since draft-ietf-httpbis-p5-range-21</a></li>
625            </ul>
626         </li>
627         <li><a href="#rfc.index">Index</a></li>
628      </ul>
629      <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a id="introduction" href="#introduction">Introduction</a></h1>
630      <p id="rfc.section.1.p.1">HTTP clients often encounter interrupted data transfers as a result of canceled requests or dropped connections. When a client
631         has stored a partial representation, it is desirable to request the remainder of that representation in a subsequent request
632         rather than transfer the entire representation. There are also a number of Web applications that benefit from being able to
633         request only a subset of a larger representation, such as a single page of a very large document or only part of an image
634         to be rendered by a device with limited local storage.
635      </p>
636      <p id="rfc.section.1.p.2">This document defines HTTP/1.1 range requests, partial responses, and the multipart/byteranges media type. The protocol for
637         range requests is an <em class="bcp14">OPTIONAL</em> feature of HTTP, designed so resources or recipients that do not implement this feature can respond as if it is a normal GET
638         request without impacting interoperability. Partial responses are indicated by a distinct status code to not be mistaken for
639         full responses by intermediate caches that might not implement the feature.
640      </p>
641      <p id="rfc.section.1.p.3">Although the HTTP range request mechanism is designed to allow for extensible range types, this specification only defines
642         requests for byte ranges.
643      </p>
644      <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a>&nbsp;<a id="conformance" href="#conformance">Conformance and Error Handling</a></h2>
645      <p id="rfc.section.1.1.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
646         in this document are to be interpreted as described in <a href="#RFC2119" id="rfc.xref.RFC2119.1"><cite title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</cite></a>.
647      </p>
648      <p id="rfc.section.1.1.p.2">Conformance criteria and considerations regarding error handling are defined in <a href="p1-messaging.html#conformance" title="Conformance and Error Handling">Section 2.5</a> of <a href="#Part1" id="rfc.xref.Part1.1"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>.
649      </p>
650      <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a>&nbsp;<a id="notation" href="#notation">Syntax Notation</a></h2>
651      <p id="rfc.section.1.2.p.1">This specification uses the Augmented Backus-Naur Form (ABNF) notation of <a href="#RFC5234" id="rfc.xref.RFC5234.1"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a> with the list rule extension defined in <a href="p1-messaging.html#notation" title="Syntax Notation">Section 1.2</a> of <a href="#Part1" id="rfc.xref.Part1.2"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>. <a href="#imported.abnf" title="Imported ABNF">Appendix&nbsp;C</a> describes rules imported from other documents. <a href="#collected.abnf" title="Collected ABNF">Appendix&nbsp;D</a> shows the collected ABNF with the list rule expanded.
652      </p>
653      <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;<a id="range.units" href="#range.units">Range Units</a></h1>
654      <p id="rfc.section.2.p.1">A representation can be partitioned into subranges according to various structural units, depending on the structure inherent
655         in the representation's media type. Such a <dfn>range unit</dfn> can be used in the <a href="#header.range" class="smpl">Range</a> (<a href="#header.range" id="rfc.xref.header.range.1" title="Range">Section&nbsp;3.1</a>) and <a href="#header.content-range" class="smpl">Content-Range</a> (<a href="#header.content-range" id="rfc.xref.header.content-range.1" title="Content-Range">Section&nbsp;4.4</a>) header fields to delineate the parts of a representation that are either requested or transferred, respectively.
656      </p>
657      <div id="rfc.figure.u.1"></div><pre class="inline"><span id="rfc.iref.g.1"></span><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span>  <a href="#range.units" class="smpl">range-unit</a>       = <a href="#range.units" class="smpl">bytes-unit</a> / <a href="#range.units" class="smpl">other-range-unit</a>
658  <a href="#range.units" class="smpl">bytes-unit</a>       = "bytes"
659  <a href="#range.units" class="smpl">other-range-unit</a> = <a href="#imported.abnf" class="smpl">token</a>
660</pre><h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;<a id="byte.ranges" href="#byte.ranges">Byte Ranges</a></h2>
661      <p id="rfc.section.2.1.p.1">Since all HTTP representations are transferred as sequences of bytes, the concept of a byte range is meaningful for any HTTP
662         representation. (However, not all clients and servers need to support byte-range operations.)
663      </p>
664      <p id="rfc.section.2.1.p.2">Byte range specifications in HTTP apply to the sequence of bytes in the representation data (not necessarily the same as the
665         message body).
666      </p>
667      <div id="rule.ranges-specifier">
668         <p id="rfc.section.2.1.p.3">                A byte range operation <em class="bcp14">MAY</em> specify a single range of bytes, or a set of ranges within a single representation.
669         </p>
670      </div>
671      <div id="rfc.figure.u.2"></div><pre class="inline"><span id="rfc.iref.g.4"></span><span id="rfc.iref.g.5"></span><span id="rfc.iref.g.6"></span><span id="rfc.iref.g.7"></span><span id="rfc.iref.g.8"></span><span id="rfc.iref.g.9"></span>  <a href="#rule.ranges-specifier" class="smpl">byte-ranges-specifier</a> = <a href="#range.units" class="smpl">bytes-unit</a> "=" <a href="#rule.ranges-specifier" class="smpl">byte-range-set</a>
672  <a href="#rule.ranges-specifier" class="smpl">byte-range-set</a>  = 1#( <a href="#rule.ranges-specifier" class="smpl">byte-range-spec</a> / <a href="#rule.ranges-specifier" class="smpl">suffix-byte-range-spec</a> )
673  <a href="#rule.ranges-specifier" class="smpl">byte-range-spec</a> = <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a> "-" [ <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> ]
674  <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a>  = 1*<a href="#imported.abnf" class="smpl">DIGIT</a>
675  <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a>   = 1*<a href="#imported.abnf" class="smpl">DIGIT</a>
676</pre><p id="rfc.section.2.1.p.5">The first-byte-pos value in a byte-range-spec gives the byte-offset of the first byte in a range. The last-byte-pos value
677         gives the byte-offset of the last byte in the range; that is, the byte positions specified are inclusive. Byte offsets start
678         at zero.
679      </p>
680      <p id="rfc.section.2.1.p.6">If the last-byte-pos value is present, it <em class="bcp14">MUST</em> be greater than or equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec is syntactically invalid. The
681         recipient of a byte-range-set that includes one or more syntactically invalid byte-range-spec values <em class="bcp14">MUST</em> ignore the header field that includes that byte-range-set.
682      </p>
683      <p id="rfc.section.2.1.p.7">If the last-byte-pos value is absent, or if the value is greater than or equal to the current length of the representation
684         data, last-byte-pos is taken to be equal to one less than the current length of the representation in bytes.
685      </p>
686      <p id="rfc.section.2.1.p.8">By its choice of last-byte-pos, a client can limit the number of bytes retrieved without knowing the size of the representation.</p>
687      <div id="rfc.figure.u.3"></div><pre class="inline"><span id="rfc.iref.g.10"></span><span id="rfc.iref.g.11"></span>  <a href="#rule.ranges-specifier" class="smpl">suffix-byte-range-spec</a> = "-" <a href="#rule.ranges-specifier" class="smpl">suffix-length</a>
688  <a href="#rule.ranges-specifier" class="smpl">suffix-length</a> = 1*<a href="#imported.abnf" class="smpl">DIGIT</a>
689</pre><p id="rfc.section.2.1.p.10">A suffix-byte-range-spec is used to specify the suffix of the representation data, of a length given by the suffix-length
690         value. (That is, this form specifies the last N bytes of a representation.) If the representation is shorter than the specified
691         suffix-length, the entire representation is used.
692      </p>
693      <p id="rfc.section.2.1.p.11">If a syntactically valid byte-range-set includes at least one byte-range-spec whose first-byte-pos is less than the current
694         length of the representation, or at least one suffix-byte-range-spec with a non-zero suffix-length, then the byte-range-set
695         is satisfiable. Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set is unsatisfiable, the server <em class="bcp14">SHOULD</em> send a response with a <a href="#status.416" class="smpl">416 (Range Not Satisfiable)</a> status code. Otherwise, the server <em class="bcp14">SHOULD</em> send a response with a <a href="#status.206" class="smpl">206 (Partial Content)</a> status code containing the satisfiable ranges of the representation.
696      </p>
697      <p id="rfc.section.2.1.p.12">In the byte range syntax, <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a>, <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a>, and <a href="#rule.ranges-specifier" class="smpl">suffix-length</a> are expressed as decimal number of octets. Since there is no predefined limit to the length of an HTTP payload, recipients <em class="bcp14">SHOULD</em> anticipate potentially large decimal numerals and prevent parsing errors due to integer conversion overflows.
698      </p>
699      <p id="rfc.section.2.1.p.13">Examples of byte-ranges-specifier values (assuming a representation of length 10000): </p>
700      <ul>
701         <li>The first 500 bytes (byte offsets 0-499, inclusive):
702            <div id="rfc.figure.u.4"></div><pre class="text">  bytes=0-499
703</pre> </li>
704         <li>The second 500 bytes (byte offsets 500-999, inclusive):
705            <div id="rfc.figure.u.5"></div><pre class="text">  bytes=500-999
706</pre> </li>
707         <li>The final 500 bytes (byte offsets 9500-9999, inclusive):
708            <div id="rfc.figure.u.6"></div><pre class="text">  bytes=-500
709</pre> Or: <div id="rfc.figure.u.7"></div><pre class="text">  bytes=9500-
710</pre> </li>
711         <li>The first and last bytes only (bytes 0 and 9999):
712            <div id="rfc.figure.u.8"></div><pre class="text">  bytes=0-0,-1
713</pre> </li>
714         <li>Several legal but not canonical specifications of the second 500 bytes (byte offsets 500-999, inclusive):
715            <div id="rfc.figure.u.9"></div><pre class="text">  bytes=500-600,601-999
716  bytes=500-700,601-999
717</pre> </li>
718      </ul>
719      <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a>&nbsp;<a id="range.units.other" href="#range.units.other">Other Range Units</a></h2>
720      <p id="rfc.section.2.2.p.1">The only range unit defined by HTTP/1.1 is "bytes" (<a href="#byte.ranges" title="Byte Ranges">Section&nbsp;2.1</a>). Additional units can be defined as described in <a href="#range.unit.registry" title="Range Unit Registry">Section&nbsp;5.1</a>.
721      </p>
722      <div id="rfc.iref.a.1"></div>
723      <h2 id="rfc.section.2.3"><a href="#rfc.section.2.3">2.3</a>&nbsp;<a id="header.accept-ranges" href="#header.accept-ranges">Accept-Ranges</a></h2>
724      <p id="rfc.section.2.3.p.1">The "Accept-Ranges" header field allows a resource to indicate its acceptance of range requests.</p>
725      <div id="rfc.figure.u.10"></div><pre class="inline"><span id="rfc.iref.g.12"></span><span id="rfc.iref.g.13"></span>  <a href="#header.accept-ranges" class="smpl">Accept-Ranges</a>     = <a href="#header.accept-ranges" class="smpl">acceptable-ranges</a>
726  <a href="#header.accept-ranges" class="smpl">acceptable-ranges</a> = 1#<a href="#range.units" class="smpl">range-unit</a> / "none"
727</pre><p id="rfc.section.2.3.p.3">Origin servers that accept byte-range requests <em class="bcp14">MAY</em> send
728      </p>
729      <div id="rfc.figure.u.11"></div><pre class="text">  Accept-Ranges: bytes
730</pre><p id="rfc.section.2.3.p.5">but are not required to do so. Clients <em class="bcp14">MAY</em> generate range requests without having received this header field for the resource involved. Range units are defined in <a href="#range.units" title="Range Units">Section&nbsp;2</a>.
731      </p>
732      <p id="rfc.section.2.3.p.6">Servers that do not accept any kind of range request for a resource <em class="bcp14">MAY</em> send
733      </p>
734      <div id="rfc.figure.u.12"></div><pre class="text">  Accept-Ranges: none
735</pre><p id="rfc.section.2.3.p.8">to advise the client not to attempt a range request.</p>
736      <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a id="range.requests" href="#range.requests">Range Requests</a></h1>
737      <div id="rfc.iref.r.1"></div>
738      <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;<a id="header.range" href="#header.range">Range</a></h2>
739      <p id="rfc.section.3.1.p.1">The "Range" header field on a GET request modifies the method semantics to request transfer of only one or more sub-ranges
740         of the selected representation data in a successful response, rather than the entire representation data.
741      </p>
742      <div id="rfc.figure.u.13"></div><pre class="inline"><span id="rfc.iref.g.14"></span>  <a href="#header.range" class="smpl">Range</a> = <a href="#rule.ranges-specifier" class="smpl">byte-ranges-specifier</a> / <a href="#header.range" class="smpl">other-ranges-specifier</a>
743  <a href="#header.range" class="smpl">other-ranges-specifier</a> = <a href="#range.units" class="smpl">other-range-unit</a> "=" <a href="#header.range" class="smpl">other-range-set</a>
744  <a href="#header.range" class="smpl">other-range-set</a> = 1*<a href="#imported.abnf" class="smpl">CHAR</a>
745</pre><p id="rfc.section.3.1.p.3">A server <em class="bcp14">MAY</em> ignore the Range header field. However, origin servers and intermediate caches ought to support byte ranges when possible,
746         since Range supports efficient recovery from partially failed transfers and partial retrieval of large representations. A
747         server <em class="bcp14">MUST</em> ignore a Range header field received with a request method other than GET.
748      </p>
749      <p id="rfc.section.3.1.p.4">An origin server <em class="bcp14">MUST</em> ignore a <a href="#header.range" class="smpl">Range</a> header field that contains a range unit it does not understand. A proxy <em class="bcp14">MAY</em> either discard a <a href="#header.range" class="smpl">Range</a> header field that contains a range unit it does not understand or pass it to the next inbound server when forwarding the request.
750      </p>
751      <p id="rfc.section.3.1.p.5">The Range header field is evaluated after evaluating the preconditions of <a href="#Part4" id="rfc.xref.Part4.1"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests">[Part4]</cite></a> and only if the result of their evaluation is leading toward a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response. In other words, Range is ignored when a conditional GET would result in a <a href="p4-conditional.html#status.304" class="smpl">304 (Not Modified)</a> response.
752      </p>
753      <p id="rfc.section.3.1.p.6">The If-Range header field (<a href="#header.if-range" id="rfc.xref.header.if-range.1" title="If-Range">Section&nbsp;3.2</a>) can be used as a precondition to applying the Range header field.
754      </p>
755      <p id="rfc.section.3.1.p.7">If all of the preconditions are true, the server supports the Range header field for the target resource, the specified range(s)
756         are syntactically correct (as defined in <a href="#byte.ranges" title="Byte Ranges">Section&nbsp;2.1</a>), and at least one of the ranges has a non-empty intersection with the current selected representation extent, then the server <em class="bcp14">MAY</em> respond with a status code of <a href="#status.206" class="smpl">206 (Partial Content)</a> and a payload containing one or more partial representations that correspond to those requested, as defined in <a href="#range.response" title="Responses to a Range Request">Section&nbsp;4</a>.
757      </p>
758      <div id="rfc.iref.i.1"></div>
759      <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a id="header.if-range" href="#header.if-range">If-Range</a></h2>
760      <p id="rfc.section.3.2.p.1">If a client has a partial copy of a representation and wishes to have an up-to-date copy of the entire representation, it
761         could use the <a href="#header.range" class="smpl">Range</a> header field with a conditional GET (using either or both of <a href="p4-conditional.html#header.if-unmodified-since" class="smpl">If-Unmodified-Since</a> and <a href="p4-conditional.html#header.if-match" class="smpl">If-Match</a>.) However, if the condition fails because the representation has been modified, the client would then have to make a second
762         request to obtain the entire current representation.
763      </p>
764      <p id="rfc.section.3.2.p.2">The "If-Range" header field allows a client to "short-circuit" the second request. Informally, its meaning is: if the representation
765         is unchanged, send me the part(s) that I am requesting in Range; otherwise, send me the entire representation.
766      </p>
767      <div id="rfc.figure.u.14"></div><pre class="inline"><span id="rfc.iref.g.15"></span>  <a href="#header.if-range" class="smpl">If-Range</a> = <a href="#imported.abnf" class="smpl">entity-tag</a> / <a href="#imported.abnf" class="smpl">HTTP-date</a>
768</pre><p id="rfc.section.3.2.p.4">Clients <em class="bcp14">MUST NOT</em> use an entity-tag marked as weak in an If-Range field value and <em class="bcp14">MUST NOT</em> use a <a href="p4-conditional.html#header.last-modified" class="smpl">Last-Modified</a> date in an If-Range field value unless it has no entity-tag for the representation and the Last-Modified date it does have
769         for the representation is strong in the sense defined by <a href="p4-conditional.html#lastmod.comparison" title="Comparison">Section 2.2.2</a> of <a href="#Part4" id="rfc.xref.Part4.2"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests">[Part4]</cite></a>.
770      </p>
771      <p id="rfc.section.3.2.p.5">A server that evaluates a conditional range request that is applicable to one of its representations <em class="bcp14">MUST</em> evaluate the condition as false if the entity-tag used as a validator is marked as weak or, when an HTTP-date is used as the
772         validator, if the date value is not strong in the sense defined by <a href="p4-conditional.html#lastmod.comparison" title="Comparison">Section 2.2.2</a> of <a href="#Part4" id="rfc.xref.Part4.3"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests">[Part4]</cite></a>. (A server can distinguish between a valid HTTP-date and any form of entity-tag by examining the first two characters.)
773      </p>
774      <p id="rfc.section.3.2.p.6">The If-Range header field <em class="bcp14">SHOULD</em> only be sent by clients together with a Range header field. The If-Range header field <em class="bcp14">MUST</em> be ignored if it is received in a request that does not include a Range header field. The If-Range header field <em class="bcp14">MUST</em> be ignored by a server that does not support the sub-range operation.
775      </p>
776      <p id="rfc.section.3.2.p.7">If the validator given in the If-Range header field matches the current validator for the selected representation of the target
777         resource, then the server <em class="bcp14">SHOULD</em> send the specified sub-range of the representation using a <a href="#status.206" class="smpl">206 (Partial Content)</a> response. If the validator does not match, then the server <em class="bcp14">SHOULD</em> send the entire representation using a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response.
778      </p>
779      <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a id="range.response" href="#range.response">Responses to a Range Request</a></h1>
780      <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;Response to a Single and Multiple Ranges Request
781      </h2>
782      <p id="rfc.section.4.1.p.1">When an HTTP message includes the content of a single range (for example, a response to a request for a single range, or to
783         a request for a set of ranges that overlap without any holes), this content is transmitted with a <a href="#header.content-range" class="smpl">Content-Range</a> header field, and a <a href="p1-messaging.html#header.content-length" class="smpl">Content-Length</a> header field showing the number of bytes actually transferred. For example,
784      </p>
785      <div id="rfc.figure.u.15"></div><pre class="text">HTTP/1.1 206 Partial Content
786Date: Wed, 15 Nov 1995 06:25:24 GMT
787Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
788Content-Range: bytes 21010-47021/47022
789Content-Length: 26012
790Content-Type: image/gif
791</pre><p id="rfc.section.4.1.p.3">When an HTTP message includes the content of multiple ranges (for example, a response to a request for multiple non-overlapping
792         ranges), these are transmitted as a multipart message. The multipart media type used for this purpose is "multipart/byteranges"
793         as defined in <a href="" title="Internet Media Type multipart/byteranges">Appendix&nbsp;A</a>.
794      </p>
795      <p id="rfc.section.4.1.p.4">A server <em class="bcp14">MAY</em> combine requested ranges when those ranges are overlapping (see <a href="#overlapping.ranges" title="Overlapping Ranges">Section&nbsp;6.1</a>).
796      </p>
797      <p id="rfc.section.4.1.p.5">A response to a request for a single range <em class="bcp14">MUST NOT</em> be sent using the multipart/byteranges media type. A response to a request for multiple ranges, whose result is a single range, <em class="bcp14">MAY</em> be sent as a multipart/byteranges media type with one part. A client that cannot decode a multipart/byteranges message <em class="bcp14">MUST NOT</em> ask for multiple ranges in a single request.
798      </p>
799      <p id="rfc.section.4.1.p.6">When a client asks for multiple ranges in one request, the server <em class="bcp14">SHOULD</em> send them in the order that they appeared in the request.
800      </p>
801      <div id="rfc.iref.18"></div>
802      <h2 id="rfc.section.4.2"><a href="#rfc.section.4.2">4.2</a>&nbsp;<a id="status.206" href="#status.206">206 Partial Content</a></h2>
803      <p id="rfc.section.4.2.p.1">The <dfn>206 (Partial Content)</dfn> status code indicates that the server has fulfilled the partial GET request for the resource. The request <em class="bcp14">MUST</em> have included a <a href="#header.range" class="smpl">Range</a> header field (<a href="#header.range" id="rfc.xref.header.range.2" title="Range">Section&nbsp;3.1</a>) indicating the desired range, and <em class="bcp14">MAY</em> have included an <a href="#header.if-range" class="smpl">If-Range</a> header field (<a href="#header.if-range" id="rfc.xref.header.if-range.2" title="If-Range">Section&nbsp;3.2</a>) to make the request conditional.
804      </p>
805      <p id="rfc.section.4.2.p.2">When a 206 response is generated, the sender <em class="bcp14">MUST</em> generate the following header fields:
806      </p>
807      <ul>
808         <li>Either a <a href="#header.content-range" class="smpl">Content-Range</a> header field (<a href="#header.content-range" id="rfc.xref.header.content-range.2" title="Content-Range">Section&nbsp;4.4</a>) indicating the range included with this response, or a multipart/byteranges <a href="p2-semantics.html#header.content-type" class="smpl">Content-Type</a> including Content-Range fields for each part. If a <a href="p1-messaging.html#header.content-length" class="smpl">Content-Length</a> header field is present in the response, its value <em class="bcp14">MUST</em> match the actual number of octets transmitted in the message body.
809         </li>
810         <li>Date</li>
811         <li> <a href="p6-cache.html#header.cache-control" class="smpl">Cache-Control</a>, <a href="p4-conditional.html#header.etag" class="smpl">ETag</a>, <a href="p6-cache.html#header.expires" class="smpl">Expires</a>, <a href="p2-semantics.html#header.content-location" class="smpl">Content-Location</a> and/or <a href="p2-semantics.html#header.vary" class="smpl">Vary</a>, if the header field would have been sent in a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response to the same request
812         </li>
813      </ul>
814      <p id="rfc.section.4.2.p.3">If a 206 is generated in response to a request with an <a href="#header.if-range" class="smpl">If-Range</a> header field, the sender <em class="bcp14">SHOULD NOT</em> generate other representation header fields beyond those described above. Otherwise, the sender <em class="bcp14">MUST</em> generate all of the same representation header fields that would have been sent in a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response to the same request.
815      </p>
816      <p id="rfc.section.4.2.p.4">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 4.1.2</a> of <a href="#Part6" id="rfc.xref.Part6.1"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Caching">[Part6]</cite></a>) to determine freshness for 206 responses.
817      </p>
818      <div id="rfc.iref.18"></div>
819      <h2 id="rfc.section.4.3"><a href="#rfc.section.4.3">4.3</a>&nbsp;<a id="status.416" href="#status.416">416 Range Not Satisfiable</a></h2>
820      <p id="rfc.section.4.3.p.1">The <dfn>416 (Range Not Satisfiable)</dfn> status code indicates that none of the ranges-specifier values in the request's <a href="#header.range" class="smpl">Range</a> header field (<a href="#header.range" id="rfc.xref.header.range.3" title="Range">Section&nbsp;3.1</a>) overlap the current extent of the selected resource and the request did not include an <a href="#header.if-range" class="smpl">If-Range</a> header field (<a href="#header.if-range" id="rfc.xref.header.if-range.3" title="If-Range">Section&nbsp;3.2</a>). (For byte-ranges, this means that the first-byte-pos of all of the byte-range-spec values were greater than the current
821         length of the selected representation.)
822      </p>
823      <p id="rfc.section.4.3.p.2">When this status code is sent in response to a byte-range request, the sender <em class="bcp14">SHOULD</em> generate a <a href="#header.content-range" class="smpl">Content-Range</a> header field specifying the current length of the selected representation (see <a href="#header.content-range" id="rfc.xref.header.content-range.3" title="Content-Range">Section&nbsp;4.4</a>).
824      </p>
825      <div id="rfc.figure.u.16"></div>
826      <p>For example:</p>  <pre class="text">HTTP/1.1 416 Range Not Satisfiable
827Date: Mon, 20 Jan 2012 15:41:54 GMT
828Content-Range: bytes */47022
829Content-Type: image/gif
830</pre><div class="note" id="rfc.section.4.3.p.4">
831         <p> <b>Note:</b> Clients cannot depend on servers to send a <a href="#status.416" class="smpl">416 (Range Not
832               Satisfiable)</a> response instead of a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response for an unsatisfiable <a href="#header.range" class="smpl">Range</a> header field, since not all servers implement this header field.
833         </p>
834      </div>
835      <div id="rfc.iref.c.1"></div>
836      <h2 id="rfc.section.4.4"><a href="#rfc.section.4.4">4.4</a>&nbsp;<a id="header.content-range" href="#header.content-range">Content-Range</a></h2>
837      <p id="rfc.section.4.4.p.1">The "Content-Range" header field is sent with a partial representation to specify where in the full representation the payload
838         body is intended to be applied.
839      </p>
840      <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></span><span id="rfc.iref.g.18"></span><span id="rfc.iref.g.19"></span><span id="rfc.iref.g.20"></span><span id="rfc.iref.g.21"></span><span id="rfc.iref.g.22"></span><span id="rfc.iref.g.23"></span>  <a href="#header.content-range" class="smpl">Content-Range</a>       = <a href="#header.content-range" class="smpl">byte-content-range</a>
841                      / <a href="#header.content-range" class="smpl">other-content-range</a>
843  <a href="#header.content-range" class="smpl">byte-content-range</a>  = <a href="#range.units" class="smpl">bytes-unit</a> <a href="#imported.abnf" class="smpl">SP</a>
844                        ( <a href="#header.content-range" class="smpl">byte-range-resp</a> / <a href="#header.content-range" class="smpl">unsatisfied-range</a> )
846  <a href="#header.content-range" class="smpl">byte-range-resp</a>     = <a href="#header.content-range" class="smpl">byte-range</a> "/" ( <a href="#header.content-range" class="smpl">complete-length</a> / "*" )
847  <a href="#header.content-range" class="smpl">byte-range</a>          = <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a> "-" <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a>
848  <a href="#header.content-range" class="smpl">unsatisfied-range</a>   = "*/" <a href="#header.content-range" class="smpl">complete-length</a>
850  <a href="#header.content-range" class="smpl">complete-length</a>     = 1*<a href="#imported.abnf" class="smpl">DIGIT</a>
852  <a href="#header.content-range" class="smpl">other-content-range</a> = <a href="#range.units" class="smpl">other-range-unit</a> <a href="#imported.abnf" class="smpl">SP</a> <a href="#header.content-range" class="smpl">other-range-resp</a>
853  <a href="#header.content-range" class="smpl">other-range-resp</a>    = *<a href="#imported.abnf" class="smpl">CHAR</a>
854</pre><p id="rfc.section.4.4.p.3">Range units are defined in <a href="#range.units" title="Range Units">Section&nbsp;2</a>. A recipient of a <a href="#status.206" class="smpl">206 (Partial Content)</a> response containing a <a href="#header.content-range" class="smpl">Content-Range</a> header field with a <a href="#range.units" class="smpl">range unit</a> that the recipient does not understand <em class="bcp14">MUST NOT</em> attempt to recombine it with a stored representation. A proxy that receives such a message <em class="bcp14">SHOULD</em> forward it downstream.
855      </p>
856      <p id="rfc.section.4.4.p.4">For byte ranges, a sender <em class="bcp14">SHOULD</em> indicate the complete length of the representation from which the range has been extracted unless the complete length is unknown
857         or difficult to determine. An asterisk character ("*") in place of the complete-length indicates that the representation length
858         was unknown when the header field was generated.
859      </p>
860      <p id="rfc.section.4.4.p.5">A Content-Range field value with a <a href="#header.content-range" class="smpl">byte-range-resp</a> that has a <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> value less than its <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a> value, or a <a href="#header.content-range" class="smpl">complete-length</a> value less than or equal to its <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> value, is invalid. The recipient of an invalid <a href="#header.content-range" class="smpl">Content-Range</a>  <em class="bcp14">MUST NOT</em> attempt to recombine the received content with a stored representation.
861      </p>
862      <p id="rfc.section.4.4.p.6">A server generating a <a href="#status.206" class="smpl">206 (Partial Content)</a> response to a byte range request <em class="bcp14">MUST</em> send, in each body-part of a multipart response or in the header block of a single part response, a Content-Range header field
863         containing a <a href="#header.content-range" class="smpl">byte-range-resp</a> value that reflects the corresponding range being sent. The following example would apply when the complete length of the
864         selected representation is known by the sender to be 1234 bytes:
865      </p>
866      <div id="rfc.figure.u.18"></div><pre class="text">  Content-Range: bytes 42-1233/1234
867</pre><p id="rfc.section.4.4.p.8">or this second example would apply when the complete length is unknown:</p>
868      <div id="rfc.figure.u.19"></div><pre class="text">  Content-Range: bytes 42-1233/*
869</pre><p id="rfc.section.4.4.p.10">A server generating a <a href="#status.416" class="smpl">416 (Range Not Satisfiable)</a> response to a byte range request <em class="bcp14">SHOULD</em> send a Content-Range header field with an <a href="#header.content-range" class="smpl">unsatisfied-range</a> value, as in the following example:
870      </p>
871      <div id="rfc.figure.u.20"></div><pre class="text">  Content-Range: bytes */1234
872</pre><p id="rfc.section.4.4.p.12">The complete-length in a 416 response indicates the current length of the selected representation, which will be known by
873         the server generating the response because that is how it determined the range to be unsatisfiable.
874      </p>
875      <p id="rfc.section.4.4.p.13">The "Content-Range" header field has no meaning for status codes that do not explicitly describe its semantic. For this specification,
876         only the <a href="#status.206" class="smpl">206 (Partial Content)</a> and <a href="#status.416" class="smpl">416 (Range Not Satisfiable)</a> status codes describe a meaning for Content-Range.
877      </p>
878      <p id="rfc.section.4.4.p.14">More examples of Content-Range values, assuming that the representation contains a total of 1234 bytes: </p>
879      <ul>
880         <li>The first 500 bytes:
881            <div id="rfc.figure.u.21"></div><pre class="text">  Content-Range: bytes 0-499/1234
882</pre> </li>
883         <li>The second 500 bytes:
884            <div id="rfc.figure.u.22"></div><pre class="text">  Content-Range: bytes 500-999/1234
885</pre> </li>
886         <li>All except for the first 500 bytes:
887            <div id="rfc.figure.u.23"></div><pre class="text">  Content-Range: bytes 500-1233/1234
888</pre> </li>
889         <li>The last 500 bytes:
890            <div id="rfc.figure.u.24"></div><pre class="text">  Content-Range: bytes 734-1233/1234
891</pre> </li>
892      </ul>
893      <h2 id="rfc.section.4.5"><a href="#rfc.section.4.5">4.5</a>&nbsp;<a id="combining.byte.ranges" href="#combining.byte.ranges">Combining Ranges</a></h2>
894      <p id="rfc.section.4.5.p.1">A response might transfer only a subrange of a representation if the connection closed prematurely or if the request used
895         one or more Range specifications. After several such transfers, a client might have received several ranges of the same representation.
896         These ranges can only be safely combined if they all have in common the same strong validator, where "strong validator" is
897         defined to be either an entity-tag that is not marked as weak (<a href="p4-conditional.html#header.etag" title="ETag">Section 2.3</a> of <a href="#Part4" id="rfc.xref.Part4.4"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests">[Part4]</cite></a>) or, if no entity-tag is provided, a <a href="p4-conditional.html#header.last-modified" class="smpl">Last-Modified</a> value that is strong in the sense defined by <a href="p4-conditional.html#lastmod.comparison" title="Comparison">Section 2.2.2</a> of <a href="#Part4" id="rfc.xref.Part4.5"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests">[Part4]</cite></a>.
898      </p>
899      <p id="rfc.section.4.5.p.2">When a client receives an incomplete <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response or a <a href="#status.206" class="smpl">206 (Partial Content)</a> response, and already has one or more partial responses for the same method and effective request URI that have the same strong
900         validator as present in the new response, the recipient <em class="bcp14">MAY</em> combine some or all of those responses into a set of continuous ranges. A client <em class="bcp14">MUST NOT</em> combine responses that differ in the strong validator or that do not have a strong validator.
901      </p>
902      <p id="rfc.section.4.5.p.3">If the new response is an incomplete <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response, then the header fields of that new response are used for any combined response and replace those of the matching
903         stored responses.
904      </p>
905      <p id="rfc.section.4.5.p.4">If the new response is a <a href="#status.206" class="smpl">206 (Partial Content)</a> response and at least one of the matching stored responses is a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a>, then the combined response header fields consist of the most recent 200 response's header fields. If all of the matching
906         stored responses are 206 responses, then the stored response with the most recent header fields is used as the source of header
907         fields for the combined response, except that the client <em class="bcp14">MUST</em> use other header fields provided in the new response, aside from <a href="#header.content-range" class="smpl">Content-Range</a>, to replace all instances of the corresponding header fields in the stored response.
908      </p>
909      <p id="rfc.section.4.5.p.5">The combined response message body consists of the union of partial content ranges in the new response and each of the selected
910         responses. If the union consists of the entire range of the representation, then the client <em class="bcp14">MUST</em> record the combined response as if it were a complete <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response, including a <a href="p1-messaging.html#header.content-length" class="smpl">Content-Length</a> header field that reflects the complete length. Otherwise, the client <em class="bcp14">MUST</em> record the set of continuous ranges as one of the following: an incomplete <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response if the combined response is a prefix of the representation, a single <a href="#status.206" class="smpl">206 (Partial Content)</a> response containing a multipart/byteranges body, or multiple <a href="#status.206" class="smpl">206 (Partial Content)</a> responses, each with one continuous range that is indicated by a <a href="#header.content-range" class="smpl">Content-Range</a> header field.
911      </p>
912      <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1>
913      <h2 id="rfc.section.5.1"><a href="#rfc.section.5.1">5.1</a>&nbsp;<a id="range.unit.registry" href="#range.unit.registry">Range Unit Registry</a></h2>
914      <p id="rfc.section.5.1.p.1">The HTTP Range Unit Registry defines the name space for the range unit names and refers to their corresponding specifications.
915         The registry is maintained at &lt;<a href=""></a>&gt;.
916      </p>
917      <h3 id="rfc.section.5.1.1"><a href="#rfc.section.5.1.1">5.1.1</a>&nbsp;<a id="range.unit.registry.procedure" href="#range.unit.registry.procedure">Procedure</a></h3>
918      <p id="rfc.section.5.1.1.p.1">Registration of an HTTP Range Unit <em class="bcp14">MUST</em> include the following fields:
919      </p>
920      <ul>
921         <li>Name</li>
922         <li>Description</li>
923         <li>Pointer to specification text</li>
924      </ul>
925      <p id="rfc.section.5.1.1.p.2">Values to be added to this name space require IETF Review (see <a href="#RFC5226" id="rfc.xref.RFC5226.1"><cite title="Guidelines for Writing an IANA Considerations Section in RFCs">[RFC5226]</cite></a>, <a href="">Section 4.1</a>).
926      </p>
927      <h3 id="rfc.section.5.1.2"><a href="#rfc.section.5.1.2">5.1.2</a>&nbsp;<a id="range.unit.registration" href="#range.unit.registration">Registrations</a></h3>
928      <p id="rfc.section.5.1.2.p.1">The initial HTTP Range Unit Registry shall contain the registrations below:</p>
929      <div id="rfc.table.1">
930         <div id="iana.range.units.table"></div>
931         <table class="tt full left" cellpadding="3" cellspacing="0">
932            <thead>
933               <tr>
934                  <th>Range Specifier Name</th>
935                  <th>Description</th>
936                  <th>Reference</th>
937               </tr>
938            </thead>
939            <tbody>
940               <tr>
941                  <td class="left">bytes</td>
942                  <td class="left">a range of octets</td>
943                  <td class="left"><a href="#range.units" title="Range Units">Section&nbsp;2</a></td>
944               </tr>
945               <tr>
946                  <td class="left">none</td>
947                  <td class="left">reserved as keyword, indicating no ranges are supported</td>
948                  <td class="left"><a href="#header.accept-ranges" id="rfc.xref.header.accept-ranges.1" title="Accept-Ranges">Section&nbsp;2.3</a></td>
949               </tr>
950            </tbody>
951         </table>
952      </div>
953      <p id="rfc.section.5.1.2.p.2">The change controller is: "IETF ( - Internet Engineering Task Force".</p>
954      <h2 id="rfc.section.5.2"><a href="#rfc.section.5.2">5.2</a>&nbsp;<a id="status.code.registration" href="#status.code.registration">Status Code Registration</a></h2>
955      <p id="rfc.section.5.2.p.1">The HTTP Status Code Registry located at &lt;<a href=""></a>&gt; shall be updated with the registrations below:
956      </p>
957      <div id="rfc.table.2">
958         <div id="iana.status.code.registration.table"></div>
959         <table class="tt full left" cellpadding="3" cellspacing="0">
960            <thead>
961               <tr>
962                  <th>Value</th>
963                  <th>Description</th>
964                  <th>Reference</th>
965               </tr>
966            </thead>
967            <tbody>
968               <tr>
969                  <td class="left">206</td>
970                  <td class="left">Partial Content</td>
971                  <td class="left"> <a href="#status.206" id="rfc.xref.status.206.1" title="206 Partial Content">Section&nbsp;4.2</a>
972                  </td>
973               </tr>
974               <tr>
975                  <td class="left">416</td>
976                  <td class="left">Range Not Satisfiable</td>
977                  <td class="left"> <a href="#status.416" id="rfc.xref.status.416.1" title="416 Range Not Satisfiable">Section&nbsp;4.3</a>
978                  </td>
979               </tr>
980            </tbody>
981         </table>
982      </div>
983      <h2 id="rfc.section.5.3"><a href="#rfc.section.5.3">5.3</a>&nbsp;<a id="header.field.registration" href="#header.field.registration">Header Field Registration</a></h2>
984      <p id="rfc.section.5.3.p.1">The Message Header Field Registry located at &lt;<a href=""></a>&gt; shall be updated with the permanent registrations below (see <a href="#BCP90" id="rfc.xref.BCP90.1"><cite title="Registration Procedures for Message Header Fields">[BCP90]</cite></a>):
985      </p>
986      <div id="rfc.table.3">
987         <div id="iana.header.registration.table"></div>
988         <table class="tt full left" cellpadding="3" cellspacing="0">
989            <thead>
990               <tr>
991                  <th>Header Field Name</th>
992                  <th>Protocol</th>
993                  <th>Status</th>
994                  <th>Reference</th>
995               </tr>
996            </thead>
997            <tbody>
998               <tr>
999                  <td class="left">Accept-Ranges</td>
1000                  <td class="left">http</td>
1001                  <td class="left">standard</td>
1002                  <td class="left"> <a href="#header.accept-ranges" id="rfc.xref.header.accept-ranges.2" title="Accept-Ranges">Section&nbsp;2.3</a>
1003                  </td>
1004               </tr>
1005               <tr>
1006                  <td class="left">Content-Range</td>
1007                  <td class="left">http</td>
1008                  <td class="left">standard</td>
1009                  <td class="left"> <a href="#header.content-range" id="rfc.xref.header.content-range.4" title="Content-Range">Section&nbsp;4.4</a>
1010                  </td>
1011               </tr>
1012               <tr>
1013                  <td class="left">If-Range</td>
1014                  <td class="left">http</td>
1015                  <td class="left">standard</td>
1016                  <td class="left"> <a href="#header.if-range" id="rfc.xref.header.if-range.4" title="If-Range">Section&nbsp;3.2</a>
1017                  </td>
1018               </tr>
1019               <tr>
1020                  <td class="left">Range</td>
1021                  <td class="left">http</td>
1022                  <td class="left">standard</td>
1023                  <td class="left"> <a href="#header.range" id="rfc.xref.header.range.4" title="Range">Section&nbsp;3.1</a>
1024                  </td>
1025               </tr>
1026            </tbody>
1027         </table>
1028      </div>
1029      <p id="rfc.section.5.3.p.2">The change controller is: "IETF ( - Internet Engineering Task Force".</p>
1030      <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a id="security.considerations" href="#security.considerations">Security Considerations</a></h1>
1031      <p id="rfc.section.6.p.1">This section is meant to inform developers, information providers, and users of known security concerns specific to the HTTP/1.1
1032         range request mechanisms. More general security considerations are addressed in HTTP messaging <a href="#Part1" id="rfc.xref.Part1.3"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a> and semantics <a href="#Part2" id="rfc.xref.Part2.1"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content">[Part2]</cite></a>.
1033      </p>
1034      <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a>&nbsp;<a id="overlapping.ranges" href="#overlapping.ranges">Overlapping Ranges</a></h2>
1035      <p id="rfc.section.6.1.p.1">Range requests containing overlapping ranges can lead to a situation where the server is sending far more data than the size
1036         of the complete resource representation.
1037      </p>
1038      <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a id="acks" href="#acks">Acknowledgments</a></h1>
1039      <p id="rfc.section.7.p.1">See <a href="p1-messaging.html#acks" title="Acknowledgments">Section 9</a> of <a href="#Part1" id="rfc.xref.Part1.4"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>.
1040      </p>
1041      <h1 id="rfc.references"><a id="rfc.section.8" href="#rfc.section.8">8.</a> References
1042      </h1>
1043      <h2 id="rfc.references.1"><a href="#rfc.section.8.1" id="rfc.section.8.1">8.1</a> Normative References
1044      </h2>
1045      <table>             
1046         <tr>
1047            <td class="reference"><b id="Part1">[Part1]</b></td>
1048            <td class="top"><a href="" title="Adobe Systems Incorporated">Fielding, R., Ed.</a> and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p1-messaging-latest (work in progress), January&nbsp;2013.
1049            </td>
1050         </tr>
1051         <tr>
1052            <td class="reference"><b id="Part2">[Part2]</b></td>
1053            <td class="top"><a href="" title="Adobe Systems Incorporated">Fielding, R., Ed.</a> and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p2-semantics-latest (work in progress), January&nbsp;2013.
1054            </td>
1055         </tr>
1056         <tr>
1057            <td class="reference"><b id="Part4">[Part4]</b></td>
1058            <td class="top"><a href="" title="Adobe Systems Incorporated">Fielding, R., Ed.</a> and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p4-conditional-latest (work in progress), January&nbsp;2013.
1059            </td>
1060         </tr>
1061         <tr>
1062            <td class="reference"><b id="Part6">[Part6]</b></td>
1063            <td class="top"><a href="" title="Adobe Systems Incorporated">Fielding, R., Ed.</a>, <a href="" title="Akamai">Nottingham, M., Ed.</a>, and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">Hypertext Transfer Protocol (HTTP/1.1): Caching</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p6-cache-latest (work in progress), January&nbsp;2013.
1064            </td>
1065         </tr>
1066         <tr>
1067            <td class="reference"><b id="RFC2046">[RFC2046]</b></td>
1068            <td class="top"><a href="" title="Innosoft International, Inc.">Freed, N.</a> and <a href="" title="First Virtual Holdings">N. Borenstein</a>, “<a href="">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</a>”, RFC&nbsp;2046, November&nbsp;1996.
1069            </td>
1070         </tr>
1071         <tr>
1072            <td class="reference"><b id="RFC2119">[RFC2119]</b></td>
1073            <td class="top"><a href="" title="Harvard University">Bradner, S.</a>, “<a href="">Key words for use in RFCs to Indicate Requirement Levels</a>”, BCP&nbsp;14, RFC&nbsp;2119, March&nbsp;1997.
1074            </td>
1075         </tr>
1076         <tr>
1077            <td class="reference"><b id="RFC5234">[RFC5234]</b></td>
1078            <td class="top"><a href="" title="Brandenburg InternetWorking">Crocker, D., Ed.</a> and <a href="" title="THUS plc.">P. Overell</a>, “<a href="">Augmented BNF for Syntax Specifications: ABNF</a>”, STD&nbsp;68, RFC&nbsp;5234, January&nbsp;2008.
1079            </td>
1080         </tr>
1081      </table>
1082      <h2 id="rfc.references.2"><a href="#rfc.section.8.2" id="rfc.section.8.2">8.2</a> Informative References
1083      </h2>
1084      <table>       
1085         <tr>
1086            <td class="reference"><b id="BCP13">[BCP13]</b></td>
1087            <td class="top"><a href="" title="Sun Microsystems">Freed, N.</a> and <a href="">J. Klensin</a>, “<a href="">Media Type Specifications and Registration Procedures</a>”, BCP&nbsp;13, RFC&nbsp;4288, December&nbsp;2005.
1088            </td>
1089         </tr>
1090         <tr>
1091            <td class="reference"><b id="BCP90">[BCP90]</b></td>
1092            <td class="top"><a href="" title="Nine by Nine">Klyne, G.</a>, <a href="" title="BEA Systems">Nottingham, M.</a>, and <a href="" title="HP Labs">J. Mogul</a>, “<a href="">Registration Procedures for Message Header Fields</a>”, BCP&nbsp;90, RFC&nbsp;3864, September&nbsp;2004.
1093            </td>
1094         </tr>
1095         <tr>
1096            <td class="reference"><b id="RFC2616">[RFC2616]</b></td>
1097            <td class="top"><a href="" title="University of California, Irvine">Fielding, R.</a>, <a href="" title="W3C">Gettys, J.</a>, <a href="" title="Compaq Computer Corporation">Mogul, J.</a>, <a href="" title="MIT Laboratory for Computer Science">Frystyk, H.</a>, <a href="" title="Xerox Corporation">Masinter, L.</a>, <a href="" title="Microsoft Corporation">Leach, P.</a>, and <a href="" title="W3C">T. Berners-Lee</a>, “<a href="">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2616, June&nbsp;1999.
1098            </td>
1099         </tr>
1100         <tr>
1101            <td class="reference"><b id="RFC5226">[RFC5226]</b></td>
1102            <td class="top"><a href="" title="IBM">Narten, T.</a> and <a href="" title="Google">H. Alvestrand</a>, “<a href="">Guidelines for Writing an IANA Considerations Section in RFCs</a>”, BCP&nbsp;26, RFC&nbsp;5226, May&nbsp;2008.
1103            </td>
1104         </tr>
1105      </table>
1106      <div class="avoidbreak">
1107         <h1 id="rfc.authors"><a href="#rfc.authors">Authors' Addresses</a></h1>
1108         <address class="vcard"><span class="vcardline"><span class="fn">Roy T. Fielding</span>
1109               (editor)
1110               <span class="n hidden"><span class="family-name">Fielding</span><span class="given-name">Roy T.</span></span></span><span class="org vcardline">Adobe Systems Incorporated</span><span class="adr"><span class="street-address vcardline">345 Park Ave</span><span class="vcardline"><span class="locality">San Jose</span>, <span class="region">CA</span>&nbsp;<span class="postal-code">95110</span></span><span class="country-name vcardline">USA</span></span><span class="vcardline">Email: <a href=""><span class="email"></span></a></span><span class="vcardline">URI: <a href="" class="url"></a></span></address>
1111         <address class="vcard"><span class="vcardline"><span class="fn">Yves Lafon</span>
1112               (editor)
1113               <span class="n hidden"><span class="family-name">Lafon</span><span class="given-name">Yves</span></span></span><span class="org vcardline">World Wide Web Consortium</span><span class="adr"><span class="street-address vcardline">W3C / ERCIM</span><span class="street-address vcardline">2004, rte des Lucioles</span><span class="vcardline"><span class="locality">Sophia-Antipolis</span>, <span class="region">AM</span>&nbsp;<span class="postal-code">06902</span></span><span class="country-name vcardline">France</span></span><span class="vcardline">Email: <a href=""><span class="email"></span></a></span><span class="vcardline">URI: <a href="" class="url"></a></span></address>
1114         <address class="vcard"><span class="vcardline"><span class="fn">Julian F. Reschke</span>
1115               (editor)
1116               <span class="n hidden"><span class="family-name">Reschke</span><span class="given-name">Julian F.</span></span></span><span class="org vcardline">greenbytes GmbH</span><span class="adr"><span class="street-address vcardline">Hafenweg 16</span><span class="vcardline"><span class="locality">Muenster</span>, <span class="region">NW</span>&nbsp;<span class="postal-code">48155</span></span><span class="country-name vcardline">Germany</span></span><span class="vcardline">Email: <a href=""><span class="email"></span></a></span><span class="vcardline">URI: <a href="" class="url"></a></span></address>
1117      </div>
1118      <div id="rfc.iref.m.1"></div>
1119      <div id="rfc.iref.m.2"></div>
1120      <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;<a id="" href="">Internet Media Type multipart/byteranges</a></h1>
1121      <p id="rfc.section.A.p.1">When an HTTP <a href="#status.206" class="smpl">206 (Partial Content)</a> response message includes the content of multiple ranges (a response to a request for multiple non-overlapping ranges), these
1122         are transmitted as a multipart message body (<a href="#RFC2046" id="rfc.xref.RFC2046.1"><cite title="Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types">[RFC2046]</cite></a>, <a href="">Section 5.1</a>). The media type for this purpose is called "multipart/byteranges". The following is to be registered with IANA <a href="#BCP13" id="rfc.xref.BCP13.1"><cite title="Media Type Specifications and Registration Procedures">[BCP13]</cite></a>.
1123      </p>
1124      <p id="rfc.section.A.p.2">The multipart/byteranges media type includes one or more parts, each with its own <a href="p2-semantics.html#header.content-type" class="smpl">Content-Type</a> and <a href="#header.content-range" class="smpl">Content-Range</a> fields. The required boundary parameter specifies the boundary string used to separate each body-part.
1125      </p>
1126      <p id="rfc.section.A.p.3"> </p>
1127      <dl>
1128         <dt>Type name:</dt>
1129         <dd>multipart</dd>
1130         <dt>Subtype name:</dt>
1131         <dd>byteranges</dd>
1132         <dt>Required parameters:</dt>
1133         <dd>boundary</dd>
1134         <dt>Optional parameters:</dt>
1135         <dd>none</dd>
1136         <dt>Encoding considerations:</dt>
1137         <dd>only "7bit", "8bit", or "binary" are permitted</dd>
1138         <dt>Security considerations:</dt>
1139         <dd>none</dd>
1140         <dt>Interoperability considerations:</dt>
1141         <dd>none</dd>
1142         <dt>Published specification:</dt>
1143         <dd>This specification (see <a href="" title="Internet Media Type multipart/byteranges">Appendix&nbsp;A</a>).
1144         </dd>
1145         <dt>Applications that use this media type:</dt>
1146         <dd>HTTP components supporting multiple ranges in a single request.</dd>
1147         <dt>Additional information:</dt>
1148         <dd>
1149            <dl>
1150               <dt>Magic number(s):</dt>
1151               <dd>none</dd>
1152               <dt>File extension(s):</dt>
1153               <dd>none</dd>
1154               <dt>Macintosh file type code(s):</dt>
1155               <dd>none</dd>
1156            </dl>
1157         </dd>
1158         <dt>Person and email address to contact for further information:</dt>
1159         <dd>See Authors Section.</dd>
1160         <dt>Intended usage:</dt>
1161         <dd>COMMON</dd>
1162         <dt>Restrictions on usage:</dt>
1163         <dd>none</dd>
1164         <dt>Author/Change controller:</dt>
1165         <dd>IESG</dd>
1166      </dl>
1167      <div class="note" id="rfc.section.A.p.4">
1168         <p> <b>Note:</b> Despite the name "multipart/byteranges" is not limited to the byte ranges only.
1169         </p>
1170      </div>
1171      <div id="rfc.figure.u.25"></div>
1172      <p>For example:</p><pre class="text">  HTTP/1.1 206 Partial Content
1173  Date: Wed, 15 Nov 1995 06:25:24 GMT
1174  Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
1175  Content-Length: 1741
1176  Content-Type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1179  Content-Type: application/pdf
1180  Content-Range: bytes 500-999/8000
1182  ...the first range...
1184  Content-Type: application/pdf
1185  Content-Range: bytes 7000-7999/8000
1187  ...the second range
1189</pre><div id="rfc.figure.u.26"></div>
1190      <p>Another example, using the "exampleunit" range unit:</p>  <pre class="text">  HTTP/1.1 206 Partial Content
1191  Date: Tue, 14 Nov 1995 06:25:24 GMT
1192  Last-Modified: Tue, 14 July 04:58:08 GMT
1193  Content-Length: 2331785
1194  Content-Type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1197  Content-Type: video/example
1198  Content-Range: exampleunit 1.2-4.3/25
1200  ...the first range...
1202  Content-Type: video/example
1203  Content-Range: exampleunit 11.2-14.3/25
1205  ...the second range
1207</pre> <p id="rfc.section.A.p.7">Notes: </p>
1208      <ol>
1209         <li>Additional CRLFs <em class="bcp14">MAY</em> precede the first boundary string in the body.
1210         </li>
1211         <li>Although <a href="#RFC2046" id="rfc.xref.RFC2046.2"><cite title="Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types">[RFC2046]</cite></a> permits the boundary string to be quoted, some existing implementations handle a quoted boundary string incorrectly.
1212         </li>
1213         <li>A number of clients and servers were coded to an early draft of the byteranges specification to use a media type of multipart/x-byteranges<span id="rfc.iref.m.3"></span><span id="rfc.iref.m.4"></span>, which is almost, but not quite compatible with the version documented in HTTP/1.1.
1214         </li>
1215      </ol>
1216      <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;<a id="changes.from.rfc.2616" href="#changes.from.rfc.2616">Changes from RFC 2616</a></h1>
1217      <p id="rfc.section.B.p.1">A weak validator cannot be used in a <a href="#status.206" class="smpl">206</a> response. (<a href="#status.206" id="rfc.xref.status.206.2" title="206 Partial Content">Section&nbsp;4.2</a>)
1218      </p>
1219      <p id="rfc.section.B.p.2">The Content-Range header field only has meaning when the status code explicitly defines its use. (<a href="#header.content-range" id="rfc.xref.header.content-range.5" title="Content-Range">Section&nbsp;4.4</a>)
1220      </p>
1221      <p id="rfc.section.B.p.3">Servers are given more leeway in how they respond to a range request, in order to mitigate abuse by malicious (or just greedy)
1222         clients.
1223      </p>
1224      <p id="rfc.section.B.p.4">multipart/byteranges can consist of a single part. (<a href="" title="Internet Media Type multipart/byteranges">Appendix&nbsp;A</a>)
1225      </p>
1226      <p id="rfc.section.B.p.5">This specification introduces a Range Specifier Registry. (<a href="#range.unit.registry" title="Range Unit Registry">Section&nbsp;5.1</a>)
1227      </p>
1228      <h1 id="rfc.section.C"><a href="#rfc.section.C">C.</a>&nbsp;<a id="imported.abnf" href="#imported.abnf">Imported ABNF</a></h1>
1229      <p id="rfc.section.C.p.1">The following core rules are included by reference, as defined in <a href="">Appendix B.1</a> of <a href="#RFC5234" id="rfc.xref.RFC5234.2"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>: ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), HEXDIG
1230         (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any visible US-ASCII
1231         character).
1232      </p>
1233      <p id="rfc.section.C.p.2">Note that all rules derived from <a href="#imported.abnf" class="smpl">token</a> are to be compared case-insensitively, like <a href="#range.units" class="smpl">range-unit</a> and <a href="#header.accept-ranges" class="smpl">acceptable-ranges</a>.
1234      </p>
1235      <p id="rfc.section.C.p.3">The rules below are defined in <a href="#Part1" id="rfc.xref.Part1.5"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>:
1236      </p>
1237      <div id="rfc.figure.u.27"></div><pre class="inline">  <a href="#imported.abnf" class="smpl">OWS</a>        = &lt;OWS, defined in <a href="#Part1" id="rfc.xref.Part1.6"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>, <a href="p1-messaging.html#whitespace" title="Whitespace">Section 3.2.3</a>&gt;
1238  <a href="#imported.abnf" class="smpl">token</a>      = &lt;token, defined in <a href="#Part1" id="rfc.xref.Part1.7"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>, <a href="p1-messaging.html#field.components" title="Field value components">Section 3.2.6</a>&gt;
1239</pre><p id="rfc.section.C.p.5">The rules below are defined in other parts:</p>
1240      <div id="rfc.figure.u.28"></div><pre class="inline">  <a href="#imported.abnf" class="smpl">HTTP-date</a>  = &lt;HTTP-date, defined in <a href="#Part2" id="rfc.xref.Part2.2"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content">[Part2]</cite></a>, <a href="" title="Date/Time Formats">Section</a>&gt;
1241  <a href="#imported.abnf" class="smpl">entity-tag</a> = &lt;entity-tag, defined in <a href="#Part4" id="rfc.xref.Part4.6"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.etag" title="ETag">Section 2.3</a>&gt;
1242</pre><h1 id="rfc.section.D"><a href="#rfc.section.D">D.</a>&nbsp;<a id="collected.abnf" href="#collected.abnf">Collected ABNF</a></h1>
1243      <div id="rfc.figure.u.29"></div> <pre class="inline"><a href="#header.accept-ranges" class="smpl">Accept-Ranges</a> = acceptable-ranges
1245<a href="#header.content-range" class="smpl">Content-Range</a> = byte-content-range / other-content-range
1247<a href="#imported.abnf" class="smpl">HTTP-date</a> = &lt;HTTP-date, defined in [Part2], Section;
1249<a href="#header.if-range" class="smpl">If-Range</a> = entity-tag / HTTP-date
1251<a href="#imported.abnf" class="smpl">OWS</a> = &lt;OWS, defined in [Part1], Section 3.2.3&gt;
1253<a href="#header.range" class="smpl">Range</a> = byte-ranges-specifier / other-ranges-specifier
1255<a href="#header.accept-ranges" class="smpl">acceptable-ranges</a> = ( *( "," OWS ) range-unit *( OWS "," [ OWS
1256 range-unit ] ) ) / "none"
1258<a href="#header.content-range" class="smpl">byte-content-range</a> = bytes-unit SP ( byte-range-resp /
1259 unsatisfied-range )
1260<a href="#header.content-range" class="smpl">byte-range</a> = first-byte-pos "-" last-byte-pos
1261<a href="#header.content-range" class="smpl">byte-range-resp</a> = byte-range "/" ( complete-length / "*" )
1262<a href="#rule.ranges-specifier" class="smpl">byte-range-set</a> = *( "," OWS ) ( byte-range-spec /
1263 suffix-byte-range-spec ) *( OWS "," [ OWS ( byte-range-spec /
1264 suffix-byte-range-spec ) ] )
1265<a href="#rule.ranges-specifier" class="smpl">byte-range-spec</a> = first-byte-pos "-" [ last-byte-pos ]
1266<a href="#rule.ranges-specifier" class="smpl">byte-ranges-specifier</a> = bytes-unit "=" byte-range-set
1267<a href="#range.units" class="smpl">bytes-unit</a> = "bytes"
1269<a href="#header.content-range" class="smpl">complete-length</a> = 1*DIGIT
1271<a href="#imported.abnf" class="smpl">entity-tag</a> = &lt;entity-tag, defined in [Part4], Section 2.3&gt;
1273<a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a> = 1*DIGIT
1275<a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> = 1*DIGIT
1277<a href="#header.content-range" class="smpl">other-content-range</a> = other-range-unit SP other-range-resp
1278<a href="#header.content-range" class="smpl">other-range-resp</a> = *CHAR
1279<a href="#header.range" class="smpl">other-range-set</a> = 1*CHAR
1280<a href="#range.units" class="smpl">other-range-unit</a> = token
1281<a href="#header.range" class="smpl">other-ranges-specifier</a> = other-range-unit "=" other-range-set
1283<a href="#range.units" class="smpl">range-unit</a> = bytes-unit / other-range-unit
1285<a href="#rule.ranges-specifier" class="smpl">suffix-byte-range-spec</a> = "-" suffix-length
1286<a href="#rule.ranges-specifier" class="smpl">suffix-length</a> = 1*DIGIT
1288<a href="#imported.abnf" class="smpl">token</a> = &lt;token, defined in [Part1], Section 3.2.6&gt;
1290<a href="#header.content-range" class="smpl">unsatisfied-range</a> = "*/" complete-length
1291</pre> <h1 id="rfc.section.E"><a href="#rfc.section.E">E.</a>&nbsp;<a id="change.log" href="#change.log">Change Log (to be removed by RFC Editor before publication)</a></h1>
1292      <p id="rfc.section.E.p.1">Changes up to the first Working Group Last Call draft are summarized in &lt;<a href=""></a>&gt;.
1293      </p>
1294      <h2 id="rfc.section.E.1"><a href="#rfc.section.E.1">E.1</a>&nbsp;<a id="changes.since.19" href="#changes.since.19">Since draft-ietf-httpbis-p5-range-19</a></h2>
1295      <p id="rfc.section.E.1.p.1">Closed issues: </p>
1296      <ul>
1297         <li> &lt;<a href=""></a>&gt;: "ABNF list expansion code problem"
1298         </li>
1299         <li> &lt;<a href=""></a>&gt;: "ABNF requirements for recipients"
1300         </li>
1301         <li> &lt;<a href=""></a>&gt;: "reserve 'none' as byte range unit"
1302         </li>
1303         <li> &lt;<a href=""></a>&gt;: "note introduction of new IANA registries as normative changes"
1304         </li>
1305         <li> &lt;<a href=""></a>&gt;: "range units vs leading zeroes vs size"
1306         </li>
1307      </ul>
1308      <h2 id="rfc.section.E.2"><a href="#rfc.section.E.2">E.2</a>&nbsp;<a id="changes.since.20" href="#changes.since.20">Since draft-ietf-httpbis-p5-range-20</a></h2>
1309      <p id="rfc.section.E.2.p.1"> </p>
1310      <ul>
1311         <li>Conformance criteria and considerations regarding error handling are now defined in Part 1.</li>
1312      </ul>
1313      <h2 id="rfc.section.E.3"><a href="#rfc.section.E.3">E.3</a>&nbsp;<a id="changes.since.21" href="#changes.since.21">Since draft-ietf-httpbis-p5-range-21</a></h2>
1314      <p id="rfc.section.E.3.p.1">None yet.</p>
1315      <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1>
1316      <p class="noprint"><a href="#rfc.index.2">2</a> <a href="#rfc.index.4">4</a> <a href="#rfc.index.A">A</a> <a href="#rfc.index.B">B</a> <a href="#rfc.index.C">C</a> <a href="#rfc.index.G">G</a> <a href="#rfc.index.I">I</a> <a href="#rfc.index.M">M</a> <a href="#rfc.index.P">P</a> <a href="#rfc.index.R">R</a>
1317      </p>
1318      <div class="print2col">
1319         <ul class="ind">
1320            <li><a id="rfc.index.2" href="#rfc.index.2"><b>2</b></a><ul>
1321                  <li>206 Partial Content (status code)&nbsp;&nbsp;<a href="#rfc.iref.18"><b>4.2</b></a>, <a href="#rfc.xref.status.206.1">5.2</a>, <a href="#rfc.xref.status.206.2">B</a></li>
1322               </ul>
1323            </li>
1324            <li><a id="rfc.index.4" href="#rfc.index.4"><b>4</b></a><ul>
1325                  <li>416 Range Not Satisfiable (status code)&nbsp;&nbsp;<a href="#rfc.iref.18"><b>4.3</b></a>, <a href="#rfc.xref.status.416.1">5.2</a></li>
1326               </ul>
1327            </li>
1328            <li><a id="rfc.index.A" href="#rfc.index.A"><b>A</b></a><ul>
1329                  <li>Accept-Ranges header field&nbsp;&nbsp;<a href="#rfc.iref.a.1"><b>2.3</b></a>, <a href="#rfc.xref.header.accept-ranges.1">5.1.2</a>, <a href="#rfc.xref.header.accept-ranges.2">5.3</a></li>
1330               </ul>
1331            </li>
1332            <li><a id="rfc.index.B" href="#rfc.index.B"><b>B</b></a><ul>
1333                  <li><em>BCP13</em>&nbsp;&nbsp;<a href="#BCP13"><b>8.2</b></a>, <a href="#rfc.xref.BCP13.1">A</a></li>
1334                  <li><em>BCP90</em>&nbsp;&nbsp;<a href="#rfc.xref.BCP90.1">5.3</a>, <a href="#BCP90"><b>8.2</b></a></li>
1335               </ul>
1336            </li>
1337            <li><a id="rfc.index.C" href="#rfc.index.C"><b>C</b></a><ul>
1338                  <li>Content-Range header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-range.1">2</a>, <a href="#rfc.xref.header.content-range.2">4.2</a>, <a href="#rfc.xref.header.content-range.3">4.3</a>, <a href="#rfc.iref.c.1"><b>4.4</b></a>, <a href="#rfc.xref.header.content-range.4">5.3</a>, <a href="#rfc.xref.header.content-range.5">B</a></li>
1339               </ul>
1340            </li>
1341            <li><a id="rfc.index.G" href="#rfc.index.G"><b>G</b></a><ul>
1342                  <li><tt>Grammar</tt>&nbsp;&nbsp;
1343                     <ul>
1344                        <li><tt>Accept-Ranges</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.12"><b>2.3</b></a></li>
1345                        <li><tt>acceptable-ranges</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.13"><b>2.3</b></a></li>
1346                        <li><tt>byte-content-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.17"><b>4.4</b></a></li>
1347                        <li><tt>byte-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.19"><b>4.4</b></a></li>
1348                        <li><tt>byte-range-resp</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.18"><b>4.4</b></a></li>
1349                        <li><tt>byte-range-set</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.6"><b>2.1</b></a></li>
1350                        <li><tt>byte-range-spec</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.7"><b>2.1</b></a></li>
1351                        <li><tt>byte-ranges-specifier</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.5"><b>2.1</b></a></li>
1352                        <li><tt>bytes-unit</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.2"><b>2</b></a></li>
1353                        <li><tt>complete-length</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.23"><b>4.4</b></a></li>
1354                        <li><tt>Content-Range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.16"><b>4.4</b></a></li>
1355                        <li><tt>first-byte-pos</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.8"><b>2.1</b></a></li>
1356                        <li><tt>If-Range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.15"><b>3.2</b></a></li>
1357                        <li><tt>last-byte-pos</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.9"><b>2.1</b></a></li>
1358                        <li><tt>other-content-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.21"><b>4.4</b></a></li>
1359                        <li><tt>other-range-resp</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.22"><b>4.4</b></a></li>
1360                        <li><tt>other-range-unit</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.3"><b>2</b></a></li>
1361                        <li><tt>Range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.14"><b>3.1</b></a></li>
1362                        <li><tt>range-unit</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.1"><b>2</b></a></li>
1363                        <li><tt>ranges-specifier</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.4"><b>2.1</b></a></li>
1364                        <li><tt>suffix-byte-range-spec</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.10"><b>2.1</b></a></li>
1365                        <li><tt>suffix-length</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.11"><b>2.1</b></a></li>
1366                        <li><tt>unsatisfied-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.20"><b>4.4</b></a></li>
1367                     </ul>
1368                  </li>
1369               </ul>
1370            </li>
1371            <li><a id="rfc.index.I" href="#rfc.index.I"><b>I</b></a><ul>
1372                  <li>If-Range header field&nbsp;&nbsp;<a href="#rfc.xref.header.if-range.1">3.1</a>, <a href="#rfc.iref.i.1"><b>3.2</b></a>, <a href="#rfc.xref.header.if-range.2">4.2</a>, <a href="#rfc.xref.header.if-range.3">4.3</a>, <a href="#rfc.xref.header.if-range.4">5.3</a></li>
1373               </ul>
1374            </li>
1375            <li><a id="rfc.index.M" href="#rfc.index.M"><b>M</b></a><ul>
1376                  <li>Media Type&nbsp;&nbsp;
1377                     <ul>
1378                        <li>multipart/byteranges&nbsp;&nbsp;<a href="#rfc.iref.m.1"><b>A</b></a></li>
1379                        <li>multipart/x-byteranges&nbsp;&nbsp;<a href="#rfc.iref.m.4">A</a></li>
1380                     </ul>
1381                  </li>
1382                  <li>multipart/byteranges Media Type&nbsp;&nbsp;<a href="#rfc.iref.m.2"><b>A</b></a></li>
1383                  <li>multipart/x-byteranges Media Type&nbsp;&nbsp;<a href="#rfc.iref.m.3">A</a></li>
1384               </ul>
1385            </li>
1386            <li><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul>
1387                  <li><em>Part1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1.1</a>, <a href="#rfc.xref.Part1.2">1.2</a>, <a href="#rfc.xref.Part1.3">6</a>, <a href="#rfc.xref.Part1.4">7</a>, <a href="#Part1"><b>8.1</b></a>, <a href="#rfc.xref.Part1.5">C</a>, <a href="#rfc.xref.Part1.6">C</a>, <a href="#rfc.xref.Part1.7">C</a><ul>
1388                        <li><em>Section 1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.2">1.2</a></li>
1389                        <li><em>Section 2.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1.1</a></li>
1390                        <li><em>Section 3.2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.6">C</a></li>
1391                        <li><em>Section 3.2.6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.7">C</a></li>
1392                        <li><em>Section 9</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.4">7</a></li>
1393                     </ul>
1394                  </li>
1395                  <li><em>Part2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.1">6</a>, <a href="#Part2"><b>8.1</b></a>, <a href="#rfc.xref.Part2.2">C</a><ul>
1396                        <li><em>Section</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.2">C</a></li>
1397                     </ul>
1398                  </li>
1399                  <li><em>Part4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.1">3.1</a>, <a href="#rfc.xref.Part4.2">3.2</a>, <a href="#rfc.xref.Part4.3">3.2</a>, <a href="#rfc.xref.Part4.4">4.5</a>, <a href="#rfc.xref.Part4.5">4.5</a>, <a href="#Part4"><b>8.1</b></a>, <a href="#rfc.xref.Part4.6">C</a><ul>
1400                        <li><em>Section 2.2.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.2">3.2</a>, <a href="#rfc.xref.Part4.3">3.2</a>, <a href="#rfc.xref.Part4.5">4.5</a></li>
1401                        <li><em>Section 2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.4">4.5</a>, <a href="#rfc.xref.Part4.6">C</a></li>
1402                     </ul>
1403                  </li>
1404                  <li><em>Part6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">4.2</a>, <a href="#Part6"><b>8.1</b></a><ul>
1405                        <li><em>Section 4.1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">4.2</a></li>
1406                     </ul>
1407                  </li>
1408               </ul>
1409            </li>
1410            <li><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul>
1411                  <li>Range header field&nbsp;&nbsp;<a href="#rfc.xref.header.range.1">2</a>, <a href="#rfc.iref.r.1"><b>3.1</b></a>, <a href="#rfc.xref.header.range.2">4.2</a>, <a href="#rfc.xref.header.range.3">4.3</a>, <a href="#rfc.xref.header.range.4">5.3</a></li>
1412                  <li><em>RFC2046</em>&nbsp;&nbsp;<a href="#RFC2046"><b>8.1</b></a>, <a href="#rfc.xref.RFC2046.1">A</a>, <a href="#rfc.xref.RFC2046.2">A</a><ul>
1413                        <li><em>Section 5.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2046.1">A</a></li>
1414                     </ul>
1415                  </li>
1416                  <li><em>RFC2119</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2119.1">1.1</a>, <a href="#RFC2119"><b>8.1</b></a></li>
1417                  <li><em>RFC2616</em>&nbsp;&nbsp;<a href="#RFC2616"><b>8.2</b></a></li>
1418                  <li><em>RFC5226</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5226.1">5.1.1</a>, <a href="#RFC5226"><b>8.2</b></a><ul>
1419                        <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5226.1">5.1.1</a></li>
1420                     </ul>
1421                  </li>
1422                  <li><em>RFC5234</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5234.1">1.2</a>, <a href="#RFC5234"><b>8.1</b></a>, <a href="#rfc.xref.RFC5234.2">C</a><ul>
1423                        <li><em>Appendix B.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5234.2">C</a></li>
1424                     </ul>
1425                  </li>
1426               </ul>
1427            </li>
1428         </ul>
1429      </div>
1430   </body>
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