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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 1.591, 2013/02/27 12:53:51, 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="2013-03-01">
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: September 2, 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">March 1, 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.22" title="Since draft-ietf-httpbis-p5-range-22">Appendix&nbsp;E.4</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 September 2, 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="#status.206">206 Partial Content</a></li>
590               <li><a href="#rfc.section.4.2">4.2</a>&nbsp;&nbsp;&nbsp;<a href="#header.content-range">Content-Range</a></li>
591               <li><a href="#rfc.section.4.3">4.3</a>&nbsp;&nbsp;&nbsp;<a href="#combining.byte.ranges">Combining Ranges</a></li>
592               <li><a href="#rfc.section.4.4">4.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.416">416 Range Not Satisfiable</a></li>
593            </ul>
594         </li>
595         <li><a href="#rfc.section.5">5.</a>&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a><ul>
596               <li><a href="#rfc.section.5.1">5.1</a>&nbsp;&nbsp;&nbsp;<a href="#range.unit.registry">Range Unit Registry</a><ul>
597                     <li><a href="#rfc.section.5.1.1">5.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#range.unit.registry.procedure">Procedure</a></li>
598                     <li><a href="#rfc.section.5.1.2">5.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#range.unit.registration">Registrations</a></li>
599                  </ul>
600               </li>
601               <li><a href="#rfc.section.5.2">5.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.registration">Status Code Registration</a></li>
602               <li><a href="#rfc.section.5.3">5.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.field.registration">Header Field Registration</a></li>
603            </ul>
604         </li>
605         <li><a href="#rfc.section.6">6.</a>&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul>
606               <li><a href="#rfc.section.6.1">6.1</a>&nbsp;&nbsp;&nbsp;<a href="#overlapping.ranges">Denial of Service Attacks using Range</a></li>
607            </ul>
608         </li>
609         <li><a href="#rfc.section.7">7.</a>&nbsp;&nbsp;&nbsp;<a href="#acks">Acknowledgments</a></li>
610         <li><a href="#rfc.section.8">8.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
611               <li><a href="#rfc.section.8.1">8.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
612               <li><a href="#rfc.section.8.2">8.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
613            </ul>
614         </li>
615         <li><a href="#rfc.authors">Authors' Addresses</a></li>
616         <li><a href="#rfc.section.A">A.</a>&nbsp;&nbsp;&nbsp;<a href="">Internet Media Type multipart/byteranges</a></li>
617         <li><a href="#rfc.section.B">B.</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></li>
618         <li><a href="#rfc.section.C">C.</a>&nbsp;&nbsp;&nbsp;<a href="#imported.abnf">Imported ABNF</a></li>
619         <li><a href="#rfc.section.D">D.</a>&nbsp;&nbsp;&nbsp;<a href="#collected.abnf">Collected ABNF</a></li>
620         <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>
621               <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>
622               <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>
623               <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>
624               <li><a href="#rfc.section.E.4">E.4</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.22">Since draft-ietf-httpbis-p5-range-22</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">Hypertext Transfer Protocol (HTTP) clients often encounter interrupted data transfers as a result of canceled requests or
631         dropped connections. When a client has stored a partial representation, it is desirable to request the remainder of that representation
632         in a subsequent request rather than transfer the entire representation. Likewise, devices with limited local storage might
633         benefit from being able to request only a subset of a larger representation, such as a single page of a very large document,
634         or the dimensions of an embedded image.
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, obsoleting those
637         parts previously defined in <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>. Range requests are an <em class="bcp14">OPTIONAL</em> feature of HTTP, designed so that recipients not implementing this feature (or not supporting it for the target resource)
638         can respond as if it is a normal GET request without impacting interoperability. Partial responses are indicated by a distinct
639         status code to not be mistaken for full responses by caches that might not implement the feature.
640      </p>
641      <p id="rfc.section.1.p.3">Although the range request mechanism is designed to allow for extensible range types, this specification only defines requests
642         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. This "<dfn>range unit</dfn>" is used in the <a href="#header.accept-ranges" class="smpl">Accept-Ranges</a> (<a href="#header.accept-ranges" id="rfc.xref.header.accept-ranges.1" title="Accept-Ranges">Section&nbsp;2.3</a>) response header field to advertise support for range requests, 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>) request header field to delineate the parts of a representation that are requested, and the <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;4.2</a>) payload header field to describe which part of a representation is being transferred.
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="#byte.ranges" class="smpl">bytes-unit</a> / <a href="#range.units.other" class="smpl">other-range-unit</a>
658</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>
659      <p id="rfc.section.2.1.p.1">Since representation data is transferred in payloads as a sequence of octets, a byte range is a meaningful substructure for
660         any representation transferable over HTTP (<a href="p2-semantics.html#representations" title="Representations">Section 3</a> of <a href="#Part2" id="rfc.xref.Part2.1"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content">[Part2]</cite></a>). We define the "bytes" range unit for expressing subranges of the data's octet sequence.
661      </p>
662      <div id="rfc.figure.u.2"></div><pre class="inline"><span id="rfc.iref.g.4"></span>  <a href="#byte.ranges" class="smpl">bytes-unit</a>       = "bytes"
663</pre><div id="rule.ranges-specifier">
664         <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.
665         </p>
666      </div>
667      <div id="rfc.figure.u.3"></div><pre class="inline"><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><span id="rfc.iref.g.10"></span>  <a href="#rule.ranges-specifier" class="smpl">byte-ranges-specifier</a> = <a href="#byte.ranges" class="smpl">bytes-unit</a> "=" <a href="#rule.ranges-specifier" class="smpl">byte-range-set</a>
668  <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> )
669  <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> ]
670  <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a>  = 1*<a href="#imported.abnf" class="smpl">DIGIT</a>
671  <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a>   = 1*<a href="#imported.abnf" class="smpl">DIGIT</a>
672</pre><p id="rfc.section.2.1.p.5">The <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a> value in a <a href="#rule.ranges-specifier" class="smpl">byte-range-spec</a> gives the byte-offset of the first byte in a range. The <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> value gives the byte-offset of the last byte in the range; that is, the byte positions specified are inclusive. Byte offsets
673         start at zero.
674      </p>
675      <p id="rfc.section.2.1.p.6">Examples of <a href="#rule.ranges-specifier" class="smpl">byte-ranges-specifier</a> values:
676      </p>
677      <ul>
678         <li>The first 500 bytes (byte offsets 0-499, inclusive):
679            <div id="rfc.figure.u.4"></div><pre class="text">  bytes=0-499
680</pre> </li>
681         <li>The second 500 bytes (byte offsets 500-999, inclusive):
682            <div id="rfc.figure.u.5"></div><pre class="text">  bytes=500-999
683</pre> </li>
684      </ul>
685      <p id="rfc.section.2.1.p.7">A <a href="#rule.ranges-specifier" class="smpl">byte-range-spec</a> is invalid if the <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> value is present and less than the <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a>.
686      </p>
687      <p id="rfc.section.2.1.p.8">A client can limit the number of bytes requested without knowing the size of the selected representation. If the <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> value is absent, or if the value is greater than or equal to the current length of the representation data, the byte range
688         is interpreted as the remainder of the representation (i.e., the server replaces the value of <a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> with a value that is one less than the current length of the selected representation).
689      </p>
690      <p id="rfc.section.2.1.p.9">A client can request the last N bytes of the selected representation using a <a href="#rule.ranges-specifier" class="smpl">suffix-byte-range-spec</a>.
691      </p>
692      <div id="rfc.figure.u.6"></div><pre class="inline"><span id="rfc.iref.g.11"></span><span id="rfc.iref.g.12"></span>  <a href="#rule.ranges-specifier" class="smpl">suffix-byte-range-spec</a> = "-" <a href="#rule.ranges-specifier" class="smpl">suffix-length</a>
693  <a href="#rule.ranges-specifier" class="smpl">suffix-length</a> = 1*<a href="#imported.abnf" class="smpl">DIGIT</a>
694</pre><p id="rfc.section.2.1.p.11">If the selected representation is shorter than the specified <a href="#rule.ranges-specifier" class="smpl">suffix-length</a>, the entire representation is used. For example (assuming a representation of length 10000):
695      </p>
696      <ul>
697         <li>The final 500 bytes (byte offsets 9500-9999, inclusive):
698            <div id="rfc.figure.u.7"></div><pre class="text">  bytes=-500
699</pre> Or: <div id="rfc.figure.u.8"></div><pre class="text">  bytes=9500-
700</pre> </li>
701         <li>The first and last bytes only (bytes 0 and 9999):
702            <div id="rfc.figure.u.9"></div><pre class="text">  bytes=0-0,-1
703</pre> </li>
704         <li>Other valid (but not canonical) specifications of the second 500 bytes (byte offsets 500-999, inclusive):
705            <div id="rfc.figure.u.10"></div><pre class="text">  bytes=500-600,601-999
706  bytes=500-700,601-999
707</pre> </li>
708      </ul>
709      <p id="rfc.section.2.1.p.12">If a valid <a href="#rule.ranges-specifier" class="smpl">byte-range-set</a> includes at least one <a href="#rule.ranges-specifier" class="smpl">byte-range-spec</a> with a <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a> that is less than the current length of the representation, or at least one <a href="#rule.ranges-specifier" class="smpl">suffix-byte-range-spec</a> with a non-zero <a href="#rule.ranges-specifier" class="smpl">suffix-length</a>, then the <a href="#rule.ranges-specifier" class="smpl">byte-range-set</a> is satisfiable. Otherwise, the <a href="#rule.ranges-specifier" class="smpl">byte-range-set</a> is unsatisfiable.
710      </p>
711      <p id="rfc.section.2.1.p.13">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 a payload, recipients ought
712         to anticipate potentially large decimal numerals and prevent parsing errors due to integer conversion overflows.
713      </p>
714      <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>
715      <p id="rfc.section.2.2.p.1">Range units are intended to be extensible. New range units ought to be registered with IANA, as defined in <a href="#range.unit.registry" title="Range Unit Registry">Section&nbsp;5.1</a>.
716      </p>
717      <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.13"></span>  <a href="#range.units.other" class="smpl">other-range-unit</a> = <a href="#imported.abnf" class="smpl">token</a>
718</pre><div id="rfc.iref.a.1"></div>
719      <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>
720      <p id="rfc.section.2.3.p.1">The "Accept-Ranges" header field allows a server to indicate that it supports range requests for the target resource.</p>
721      <div id="rfc.figure.u.12"></div><pre class="inline"><span id="rfc.iref.g.14"></span><span id="rfc.iref.g.15"></span>  <a href="#header.accept-ranges" class="smpl">Accept-Ranges</a>     = <a href="#header.accept-ranges" class="smpl">acceptable-ranges</a>
722  <a href="#header.accept-ranges" class="smpl">acceptable-ranges</a> = 1#<a href="#range.units" class="smpl">range-unit</a> / "none"
723</pre><p id="rfc.section.2.3.p.3">Origin servers that support byte-range requests <em class="bcp14">MAY</em> send
724      </p>
725      <div id="rfc.figure.u.13"></div><pre class="text">  Accept-Ranges: bytes
726</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>.
727      </p>
728      <p id="rfc.section.2.3.p.6">Servers that do not support any kind of range request for the target resource resource <em class="bcp14">MAY</em> send
729      </p>
730      <div id="rfc.figure.u.14"></div><pre class="text">  Accept-Ranges: none
731</pre><p id="rfc.section.2.3.p.8">to advise the client not to attempt a range request.</p>
732      <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a id="range.requests" href="#range.requests">Range Requests</a></h1>
733      <div id="rfc.iref.r.1"></div>
734      <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>
735      <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 subranges
736         of the selected representation data, rather than the entire selected representation data.
737      </p>
738      <div id="rfc.figure.u.15"></div><pre class="inline"><span id="rfc.iref.g.16"></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>
739  <a href="#header.range" class="smpl">other-ranges-specifier</a> = <a href="#range.units.other" class="smpl">other-range-unit</a> "=" <a href="#header.range" class="smpl">other-range-set</a>
740  <a href="#header.range" class="smpl">other-range-set</a> = 1*<a href="#imported.abnf" class="smpl">CHAR</a>
741</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,
742         since Range supports efficient recovery from partially failed transfers and partial retrieval of large representations. A
743         server <em class="bcp14">MUST</em> ignore a Range header field received with a request method other than GET.
744      </p>
745      <p id="rfc.section.3.1.p.4">An origin server <em class="bcp14">MUST</em> ignore a Range header field that contains a range unit it does not understand. A proxy <em class="bcp14">MAY</em> either discard a Range header field that contains a range unit it does not understand or pass it to the next inbound server
746         when forwarding the request.
747      </p>
748      <p id="rfc.section.3.1.p.5">A server that supports range requests ought to ignore or reject a <a href="#header.range" class="smpl">Range</a> header field that consists of more than two overlapping ranges, or a set of many small ranges that are not listed in ascending
749         order, since both are indications of either a broken client or a deliberate denial of service attack (<a href="#overlapping.ranges" title="Denial of Service Attacks using Range">Section&nbsp;6.1</a>). A client <em class="bcp14">SHOULD NOT</em> request multiple ranges that are inherently less efficient to process and transfer than a single range that encompasses the
750         same data.
751      </p>
752      <p id="rfc.section.3.1.p.6">A client that is requesting multiple ranges <em class="bcp14">SHOULD</em> list those ranges in ascending order (the order in which they would typically be received in a complete representation) unless
753         there is a specific need to request a later part earlier. For example, a user agent processing a large representation with
754         an internal catalog of parts might need to request later parts first, particularly if the representation consists of pages
755         stored in reverse order and the user agent wishes to transfer one page at a time.
756      </p>
757      <p id="rfc.section.3.1.p.7">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.
758      </p>
759      <p id="rfc.section.3.1.p.8">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.
760      </p>
761      <p id="rfc.section.3.1.p.9">If all of the preconditions are true, the server supports the Range header field for the target resource, and the specified
762         range(s) are valid and satisfiable (as defined in <a href="#byte.ranges" title="Byte Ranges">Section&nbsp;2.1</a>), the server <em class="bcp14">SHOULD</em> send a <a href="#status.206" class="smpl">206 (Partial Content)</a> response with a payload containing one or more partial representations that correspond to the satisfiable ranges requested,
763         as defined in <a href="#range.response" title="Responses to a Range Request">Section&nbsp;4</a>.
764      </p>
765      <p id="rfc.section.3.1.p.10">If all of the preconditions are true, the server supports the Range header field for the target resource, and the specified
766         range(s) are invalid or unsatisfiable, the server <em class="bcp14">SHOULD</em> send a <a href="#status.416" class="smpl">416 (Range Not Satisfiable)</a> response.
767      </p>
768      <div id="rfc.iref.i.1"></div>
769      <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>
770      <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
771         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
772         request to obtain the entire current representation.
773      </p>
774      <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
775         is unchanged, send me the part(s) that I am requesting in Range; otherwise, send me the entire representation.
776      </p>
777      <div id="rfc.figure.u.16"></div><pre class="inline"><span id="rfc.iref.g.17"></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>
778</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
779         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>.
780      </p>
781      <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
782         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.)
783      </p>
784      <p id="rfc.section.3.2.p.6">A client <em class="bcp14">MUST NOT</em> generate an If-Range header field in a request that does not contain a <a href="#header.range" class="smpl">Range</a> header field. A server <em class="bcp14">MUST</em> ignore an If-Range header field received in a request that does not contain a <a href="#header.range" class="smpl">Range</a> header field. An origin server <em class="bcp14">MUST</em> ignore an If-Range header field received in a request for a target resource that does not support Range requests.
785      </p>
786      <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
787         resource, then the server <em class="bcp14">SHOULD</em> process the Range header field as requested. If the validator does not match, then the server <em class="bcp14">MUST</em> ignore the <a href="#header.range" class="smpl">Range</a> header field.
788      </p>
789      <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>
790      <div id="rfc.iref.20"></div>
791      <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;<a id="status.206" href="#status.206">206 Partial Content</a></h2>
792      <p id="rfc.section.4.1.p.1">The <dfn>206 (Partial Content)</dfn> status code indicates that the server is successfully fulfilling a range request for the target resource by transferring one
793         or more parts of the selected representation that correspond to the satisfiable ranges found in the requests's <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>).
794      </p>
795      <p id="rfc.section.4.1.p.2">If a single part is being transferred, the server generating the 206 response <em class="bcp14">MUST</em> generate a <a href="#header.content-range" class="smpl">Content-Range</a> header field, describing what range of the selected representation is enclosed, and a payload consisting of the range. For
796         example:
797      </p>
798      <div id="rfc.figure.u.17"></div><pre class="text">HTTP/1.1 206 Partial Content
799Date: Wed, 15 Nov 1995 06:25:24 GMT
800Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
801Content-Range: bytes 21010-47021/47022
802Content-Length: 26012
803Content-Type: image/gif
805... 26012 bytes of partial image data ...
806</pre><p id="rfc.section.4.1.p.4">If multiple parts are being transferred, the server generating the 206 response <em class="bcp14">MUST</em> generate a "multipart/byteranges" payload, as defined in <a href="" title="Internet Media Type multipart/byteranges">Appendix&nbsp;A</a>, and a <a href="p2-semantics.html#header.content-type" class="smpl">Content-Type</a> header field containing the multipart/byteranges media type and its required boundary parameter. To avoid confusion with single
807         part responses, a server <em class="bcp14">MUST NOT</em> generate a <a href="#header.content-range" class="smpl">Content-Range</a> header field in the HTTP header block of a multiple part response (this field will be sent in each part instead).
808      </p>
809      <p id="rfc.section.4.1.p.5">Within the header area of each body part in the multipart payload, the server <em class="bcp14">MUST</em> generate a <a href="#header.content-range" class="smpl">Content-Range</a> header field corresponding to the range being enclosed in that body part. If the selected representation would have had a <a href="p2-semantics.html#header.content-type" class="smpl">Content-Type</a> header field in a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response, the server <em class="bcp14">SHOULD</em> generate that same <a href="p2-semantics.html#header.content-type" class="smpl">Content-Type</a> field in the header area of each body part. For example:
810      </p>
811      <div id="rfc.figure.u.18"></div><pre class="text">HTTP/1.1 206 Partial Content
812Date: Wed, 15 Nov 1995 06:25:24 GMT
813Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
814Content-Length: 1741
815Content-Type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
818Content-Type: application/pdf
819Content-Range: bytes 500-999/8000
821...the first range...
823Content-Type: application/pdf
824Content-Range: bytes 7000-7999/8000
826...the second range
828</pre><p id="rfc.section.4.1.p.7">When multiple ranges are requested, a server <em class="bcp14">MAY</em> coalesce any of the ranges that overlap or that are separated by a gap that is smaller than the overhead of sending multiple
829         parts, regardless of the order in which the corresponding byte-range-spec appeared in the received <a href="#header.range" class="smpl">Range</a> header field. Since the typical overhead between parts of a multipart/byteranges payload is around 80 bytes, depending on
830         the selected representation's media type and the chosen boundary parameter length, it can be less efficient to transfer many
831         small disjoint parts than it is to transfer the entire selected representation.
832      </p>
833      <p id="rfc.section.4.1.p.8">A server <em class="bcp14">MUST NOT</em> generate a multipart response to a request for a single range, since a client that does not request multiple parts might not
834         support multipart responses. However, a server <em class="bcp14">MAY</em> generate a multipart/byteranges payload with only a single body part if multiple ranges were requested and only one range
835         was found to be satisfiable or only one range remained after coalescing. A client that cannot process a multipart/byteranges
836         response <em class="bcp14">MUST NOT</em> ask for multiple ranges in a single request.
837      </p>
838      <p id="rfc.section.4.1.p.9">When a multipart response payload is generated, the server <em class="bcp14">SHOULD</em> send the parts in the same order that the corresponding byte-range-spec appeared in the received <a href="#header.range" class="smpl">Range</a> header field, excluding those ranges that were deemed unsatisfiable or that were coalesced into other ranges. A client that
839         receives a multipart response <em class="bcp14">MUST</em> inspect the <a href="#header.content-range" class="smpl">Content-Range</a> header field present in each body part in order to determine which range is contained in that body part; a client cannot rely
840         on receiving the same ranges that it requested, nor the same order that it requested.
841      </p>
842      <p id="rfc.section.4.1.p.10">When a 206 response is generated, the server <em class="bcp14">MUST</em> generate the following header fields, in addition to those required above, if the field would have been sent in a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response to the same request: <a href="" class="smpl">Date</a>, <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 <a href="p2-semantics.html#header.vary" class="smpl">Vary</a>.
843      </p>
844      <p id="rfc.section.4.1.p.11">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 required above, because the client is understood to already have
845         a prior response containing those header fields. Otherwise, the sender <em class="bcp14">MUST</em> generate all of the 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.
846      </p>
847      <p id="rfc.section.4.1.p.12">A 206 response is cacheable unless otherwise indicated by explicit cache controls (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>).
848      </p>
849      <div id="rfc.iref.c.1"></div>
850      <h2 id="rfc.section.4.2"><a href="#rfc.section.4.2">4.2</a>&nbsp;<a id="header.content-range" href="#header.content-range">Content-Range</a></h2>
851      <p id="rfc.section.4.2.p.1">The "Content-Range" header field is sent in a single part <a href="#status.206" class="smpl">206 (Partial Content)</a> response to indicate the partial range of the selected representation enclosed as the message payload, sent in each part of
852         a multipart 206 response to indicate the range enclosed within each body part, and sent in <a href="#status.416" class="smpl">416 (Range Not Satisfiable)</a> responses to provide information about the selected representation.
853      </p>
854      <div id="rfc.figure.u.19"></div><pre class="inline"><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><span id="rfc.iref.g.24"></span><span id="rfc.iref.g.25"></span>  <a href="#header.content-range" class="smpl">Content-Range</a>       = <a href="#header.content-range" class="smpl">byte-content-range</a>
855                      / <a href="#header.content-range" class="smpl">other-content-range</a>
857  <a href="#header.content-range" class="smpl">byte-content-range</a>  = <a href="#byte.ranges" class="smpl">bytes-unit</a> <a href="#imported.abnf" class="smpl">SP</a>
858                        ( <a href="#header.content-range" class="smpl">byte-range-resp</a> / <a href="#header.content-range" class="smpl">unsatisfied-range</a> )
860  <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> / "*" )
861  <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>
862  <a href="#header.content-range" class="smpl">unsatisfied-range</a>   = "*/" <a href="#header.content-range" class="smpl">complete-length</a>
864  <a href="#header.content-range" class="smpl">complete-length</a>     = 1*<a href="#imported.abnf" class="smpl">DIGIT</a>
866  <a href="#header.content-range" class="smpl">other-content-range</a> = <a href="#range.units.other" 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>
867  <a href="#header.content-range" class="smpl">other-range-resp</a>    = *<a href="#imported.abnf" class="smpl">CHAR</a>
868</pre><p id="rfc.section.4.2.p.3">If a <a href="#status.206" class="smpl">206 (Partial Content)</a> response contains a <a href="#header.content-range" class="smpl">Content-Range</a> header field with a <a href="#range.units" class="smpl">range unit</a> (<a href="#range.units" title="Range Units">Section&nbsp;2</a>) that the recipient does not understand, the recipient <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.
869      </p>
870      <p id="rfc.section.4.2.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
871         unknown or difficult to determine. An asterisk character ("*") in place of the complete-length indicates that the representation
872         length was unknown when the header field was generated.
873      </p>
874      <p id="rfc.section.4.2.p.5">The following example illustrates when the complete length of the selected representation is known by the sender to be 1234
875         bytes:
876      </p>
877      <div id="rfc.figure.u.20"></div><pre class="text">  Content-Range: bytes 42-1233/1234
878</pre><p id="rfc.section.4.2.p.7">and this second example illustrates when the complete length is unknown:</p>
879      <div id="rfc.figure.u.21"></div><pre class="text">  Content-Range: bytes 42-1233/*
880</pre><p id="rfc.section.4.2.p.9">A Content-Range field value is invalid if it contains 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. 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.
881      </p>
882      <p id="rfc.section.4.2.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:
883      </p>
884      <div id="rfc.figure.u.22"></div><pre class="text">  Content-Range: bytes */1234
885</pre><p id="rfc.section.4.2.p.12">The complete-length in a 416 response indicates the current length of the selected representation.</p>
886      <p id="rfc.section.4.2.p.13">The "Content-Range" header field has no meaning for status codes that do not explicitly describe its semantic. For this specification,
887         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.
888      </p>
889      <p id="rfc.section.4.2.p.14">The following are examples of Content-Range values in which the selected representation contains a total of 1234 bytes: </p>
890      <ul>
891         <li>The first 500 bytes:
892            <div id="rfc.figure.u.23"></div><pre class="text">  Content-Range: bytes 0-499/1234
893</pre> </li>
894         <li>The second 500 bytes:
895            <div id="rfc.figure.u.24"></div><pre class="text">  Content-Range: bytes 500-999/1234
896</pre> </li>
897         <li>All except for the first 500 bytes:
898            <div id="rfc.figure.u.25"></div><pre class="text">  Content-Range: bytes 500-1233/1234
899</pre> </li>
900         <li>The last 500 bytes:
901            <div id="rfc.figure.u.26"></div><pre class="text">  Content-Range: bytes 734-1233/1234
902</pre> </li>
903      </ul>
904      <h2 id="rfc.section.4.3"><a href="#rfc.section.4.3">4.3</a>&nbsp;<a id="combining.byte.ranges" href="#combining.byte.ranges">Combining Ranges</a></h2>
905      <p id="rfc.section.4.3.p.1">A response might transfer only a subrange of a representation if the connection closed prematurely or if the request used
906         one or more Range specifications. After several such transfers, a client might have received several ranges of the same representation.
907         These ranges can only be safely combined if they all have in common the same strong validator, where "strong validator" is
908         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>.
909      </p>
910      <p id="rfc.section.4.3.p.2">A client that has received multiple partial responses to GET requests on a target resource <em class="bcp14">MAY</em> combine those responses into a larger continuous range if they share the same strong validator.
911      </p>
912      <p id="rfc.section.4.3.p.3">If the most recent response is an incomplete <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> response, then the header fields of that response are used for any combined response and replace those of the matching stored
913         responses.
914      </p>
915      <p id="rfc.section.4.3.p.4">If the most recent 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
916         stored responses are 206 responses, then the stored response with the most recent header fields is used as the source of header
917         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.
918      </p>
919      <p id="rfc.section.4.3.p.5">The combined response message body consists of the union of partial content ranges in the new response and each of the selected
920         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.
921      </p>
922      <div id="rfc.iref.29"></div>
923      <h2 id="rfc.section.4.4"><a href="#rfc.section.4.4">4.4</a>&nbsp;<a id="status.416" href="#status.416">416 Range Not Satisfiable</a></h2>
924      <p id="rfc.section.4.4.p.1">The <dfn>416 (Range Not Satisfiable)</dfn> status code indicates that none of the ranges 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 or that the set of ranges requested has been rejected due to invalid
925         ranges or an excessive request of small or overlapping ranges.
926      </p>
927      <p id="rfc.section.4.4.p.2">For byte ranges, failing to overlap the current extent means that the <a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a> of all of the <a href="#rule.ranges-specifier" class="smpl">byte-range-spec</a> values were greater than the current length of the selected representation. When this status code is generated in response
928         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 (<a href="#header.content-range" id="rfc.xref.header.content-range.2" title="Content-Range">Section&nbsp;4.2</a>).
929      </p>
930      <div id="rfc.figure.u.27"></div>
931      <p>For example:</p>  <pre class="text">HTTP/1.1 416 Range Not Satisfiable
932Date: Mon, 20 Jan 2012 15:41:54 GMT
933Content-Range: bytes */47022
934</pre><div class="note" id="rfc.section.4.4.p.4">
935         <p> <b>Note:</b> Because servers are free to ignore <a href="#header.range" class="smpl">Range</a>, many implementations will simply respond with <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> if the requested ranges are invalid or not satisfiable. That is partly because most clients are prepared to receive a <a href="p2-semantics.html#status.200" class="smpl">200 (OK)</a> to complete the task (albeit less efficiently) and partly because clients might not stop making an invalid partial request
936            until they have received a complete representation. Thus, clients cannot depend on receiving a <a href="#status.416" class="smpl">416 (Range Not Satisfiable)</a> response even when it is most appropriate.
937         </p>
938      </div>
939      <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1>
940      <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>
941      <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.
942         The registry is maintained at &lt;<a href=""></a>&gt;.
943      </p>
944      <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>
945      <p id="rfc.section.5.1.1.p.1">Registration of an HTTP Range Unit <em class="bcp14">MUST</em> include the following fields:
946      </p>
947      <ul>
948         <li>Name</li>
949         <li>Description</li>
950         <li>Pointer to specification text</li>
951      </ul>
952      <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>).
953      </p>
954      <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>
955      <p id="rfc.section.5.1.2.p.1">The initial HTTP Range Unit Registry shall contain the registrations below:</p>
956      <div id="rfc.table.1">
957         <div id="iana.range.units.table"></div>
958         <table class="tt full left" cellpadding="3" cellspacing="0">
959            <thead>
960               <tr>
961                  <th>Range Unit Name</th>
962                  <th>Description</th>
963                  <th>Reference</th>
964               </tr>
965            </thead>
966            <tbody>
967               <tr>
968                  <td class="left">bytes</td>
969                  <td class="left">a range of octets</td>
970                  <td class="left"><a href="#byte.ranges" title="Byte Ranges">Section&nbsp;2.1</a></td>
971               </tr>
972               <tr>
973                  <td class="left">none</td>
974                  <td class="left">reserved as keyword, indicating no ranges are supported</td>
975                  <td class="left"><a href="#header.accept-ranges" id="rfc.xref.header.accept-ranges.2" title="Accept-Ranges">Section&nbsp;2.3</a></td>
976               </tr>
977            </tbody>
978         </table>
979      </div>
980      <p id="rfc.section.5.1.2.p.2">The change controller is: "IETF ( - Internet Engineering Task Force".</p>
981      <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>
982      <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:
983      </p>
984      <div id="rfc.table.2">
985         <div id="iana.status.code.registration.table"></div>
986         <table class="tt full left" cellpadding="3" cellspacing="0">
987            <thead>
988               <tr>
989                  <th>Value</th>
990                  <th>Description</th>
991                  <th>Reference</th>
992               </tr>
993            </thead>
994            <tbody>
995               <tr>
996                  <td class="left">206</td>
997                  <td class="left">Partial Content</td>
998                  <td class="left"> <a href="#status.206" id="rfc.xref.status.206.1" title="206 Partial Content">Section&nbsp;4.1</a>
999                  </td>
1000               </tr>
1001               <tr>
1002                  <td class="left">416</td>
1003                  <td class="left">Range Not Satisfiable</td>
1004                  <td class="left"> <a href="#status.416" id="rfc.xref.status.416.1" title="416 Range Not Satisfiable">Section&nbsp;4.4</a>
1005                  </td>
1006               </tr>
1007            </tbody>
1008         </table>
1009      </div>
1010      <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>
1011      <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>):
1012      </p>
1013      <div id="rfc.table.3">
1014         <div id="iana.header.registration.table"></div>
1015         <table class="tt full left" cellpadding="3" cellspacing="0">
1016            <thead>
1017               <tr>
1018                  <th>Header Field Name</th>
1019                  <th>Protocol</th>
1020                  <th>Status</th>
1021                  <th>Reference</th>
1022               </tr>
1023            </thead>
1024            <tbody>
1025               <tr>
1026                  <td class="left">Accept-Ranges</td>
1027                  <td class="left">http</td>
1028                  <td class="left">standard</td>
1029                  <td class="left"> <a href="#header.accept-ranges" id="rfc.xref.header.accept-ranges.3" title="Accept-Ranges">Section&nbsp;2.3</a>
1030                  </td>
1031               </tr>
1032               <tr>
1033                  <td class="left">Content-Range</td>
1034                  <td class="left">http</td>
1035                  <td class="left">standard</td>
1036                  <td class="left"> <a href="#header.content-range" id="rfc.xref.header.content-range.3" title="Content-Range">Section&nbsp;4.2</a>
1037                  </td>
1038               </tr>
1039               <tr>
1040                  <td class="left">If-Range</td>
1041                  <td class="left">http</td>
1042                  <td class="left">standard</td>
1043                  <td class="left"> <a href="#header.if-range" id="rfc.xref.header.if-range.2" title="If-Range">Section&nbsp;3.2</a>
1044                  </td>
1045               </tr>
1046               <tr>
1047                  <td class="left">Range</td>
1048                  <td class="left">http</td>
1049                  <td class="left">standard</td>
1050                  <td class="left"> <a href="#header.range" id="rfc.xref.header.range.4" title="Range">Section&nbsp;3.1</a>
1051                  </td>
1052               </tr>
1053            </tbody>
1054         </table>
1055      </div>
1056      <p id="rfc.section.5.3.p.2">The change controller is: "IETF ( - Internet Engineering Task Force".</p>
1057      <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a id="security.considerations" href="#security.considerations">Security Considerations</a></h1>
1058      <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
1059         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.Part2.2"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content">[Part2]</cite></a>.
1060      </p>
1061      <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a>&nbsp;<a id="overlapping.ranges" href="#overlapping.ranges">Denial of Service Attacks using Range</a></h2>
1062      <p id="rfc.section.6.1.p.1">Unconstrained multiple range requests are susceptible to denial of service attacks because the effort required to request
1063         many overlapping ranges of the same data is tiny compared to the time, memory, and bandwidth consumed by attempting to serve
1064         the requested data in many parts. Servers ought to ignore, coalesce, or reject egregious range requests, such as requests
1065         for more than two overlapping ranges or for many small ranges in a single set, particularly when the ranges are requested
1066         out of order for no apparent reason. Multipart range requests are not designed to support random access.
1067      </p>
1068      <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a id="acks" href="#acks">Acknowledgments</a></h1>
1069      <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>.
1070      </p>
1071      <h1 id="rfc.references"><a id="rfc.section.8" href="#rfc.section.8">8.</a> References
1072      </h1>
1073      <h2 id="rfc.references.1"><a href="#rfc.section.8.1" id="rfc.section.8.1">8.1</a> Normative References
1074      </h2>
1075      <table>             
1076         <tr>
1077            <td class="reference"><b id="Part1">[Part1]</b></td>
1078            <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), March&nbsp;2013.
1079            </td>
1080         </tr>
1081         <tr>
1082            <td class="reference"><b id="Part2">[Part2]</b></td>
1083            <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), March&nbsp;2013.
1084            </td>
1085         </tr>
1086         <tr>
1087            <td class="reference"><b id="Part4">[Part4]</b></td>
1088            <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), March&nbsp;2013.
1089            </td>
1090         </tr>
1091         <tr>
1092            <td class="reference"><b id="Part6">[Part6]</b></td>
1093            <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), March&nbsp;2013.
1094            </td>
1095         </tr>
1096         <tr>
1097            <td class="reference"><b id="RFC2046">[RFC2046]</b></td>
1098            <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.
1099            </td>
1100         </tr>
1101         <tr>
1102            <td class="reference"><b id="RFC2119">[RFC2119]</b></td>
1103            <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.
1104            </td>
1105         </tr>
1106         <tr>
1107            <td class="reference"><b id="RFC5234">[RFC5234]</b></td>
1108            <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.
1109            </td>
1110         </tr>
1111      </table>
1112      <h2 id="rfc.references.2"><a href="#rfc.section.8.2" id="rfc.section.8.2">8.2</a> Informative References
1113      </h2>
1114      <table>       
1115         <tr>
1116            <td class="reference"><b id="BCP13">[BCP13]</b></td>
1117            <td class="top"><a href="" title="Oracle">Freed, N.</a>, <a href="">Klensin, J.</a>, and <a href="" title="AT&amp;T Laboratories">T. Hansen</a>, “<a href="">Media Type Specifications and Registration Procedures</a>”, BCP&nbsp;13, RFC&nbsp;6838, January&nbsp;2013.
1118            </td>
1119         </tr>
1120         <tr>
1121            <td class="reference"><b id="BCP90">[BCP90]</b></td>
1122            <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.
1123            </td>
1124         </tr>
1125         <tr>
1126            <td class="reference"><b id="RFC2616">[RFC2616]</b></td>
1127            <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.
1128            </td>
1129         </tr>
1130         <tr>
1131            <td class="reference"><b id="RFC5226">[RFC5226]</b></td>
1132            <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.
1133            </td>
1134         </tr>
1135      </table>
1136      <div class="avoidbreak">
1137         <h1 id="rfc.authors"><a href="#rfc.authors">Authors' Addresses</a></h1>
1138         <address class="vcard"><span class="vcardline"><span class="fn">Roy T. Fielding</span>
1139               (editor)
1140               <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>
1141         <address class="vcard"><span class="vcardline"><span class="fn">Yves Lafon</span>
1142               (editor)
1143               <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>
1144         <address class="vcard"><span class="vcardline"><span class="fn">Julian F. Reschke</span>
1145               (editor)
1146               <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>
1147      </div>
1148      <div id="rfc.iref.m.1"></div>
1149      <div id="rfc.iref.m.2"></div>
1150      <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>
1151      <p id="rfc.section.A.p.1">When a <a href="#status.206" class="smpl">206 (Partial Content)</a> response message includes the content of multiple ranges, they are transmitted as body parts in 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>) with the media type of "multipart/byteranges". The following definition 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>.
1152      </p>
1153      <p id="rfc.section.A.p.2">The multipart/byteranges media type includes one or more body 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.
1154      </p>
1155      <p id="rfc.section.A.p.3"> </p>
1156      <dl>
1157         <dt>Type name:</dt>
1158         <dd>multipart</dd>
1159         <dt>Subtype name:</dt>
1160         <dd>byteranges</dd>
1161         <dt>Required parameters:</dt>
1162         <dd>boundary</dd>
1163         <dt>Optional parameters:</dt>
1164         <dd>none</dd>
1165         <dt>Encoding considerations:</dt>
1166         <dd>only "7bit", "8bit", or "binary" are permitted</dd>
1167         <dt>Security considerations:</dt>
1168         <dd>none</dd>
1169         <dt>Interoperability considerations:</dt>
1170         <dd>none</dd>
1171         <dt>Published specification:</dt>
1172         <dd>This specification (see <a href="" title="Internet Media Type multipart/byteranges">Appendix&nbsp;A</a>).
1173         </dd>
1174         <dt>Applications that use this media type:</dt>
1175         <dd>HTTP components supporting multiple ranges in a single request.</dd>
1176         <dt>Additional information:</dt>
1177         <dd>
1178            <dl>
1179               <dt>Magic number(s):</dt>
1180               <dd>none</dd>
1181               <dt>File extension(s):</dt>
1182               <dd>none</dd>
1183               <dt>Macintosh file type code(s):</dt>
1184               <dd>none</dd>
1185            </dl>
1186         </dd>
1187         <dt>Person and email address to contact for further information:</dt>
1188         <dd>See Authors Section.</dd>
1189         <dt>Intended usage:</dt>
1190         <dd>COMMON</dd>
1191         <dt>Restrictions on usage:</dt>
1192         <dd>none</dd>
1193         <dt>Author/Change controller:</dt>
1194         <dd>IESG</dd>
1195      </dl>
1196      <p id="rfc.section.A.p.4">Implementation Notes: </p>
1197      <ol>
1198         <li>Additional CRLFs might precede the first boundary string in the body.</li>
1199         <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.
1200         </li>
1201         <li>A number of clients and servers were coded to an early draft of the byteranges specification that used 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 this type.
1202         </li>
1203      </ol>
1204      <p id="rfc.section.A.p.5">Despite the name, the "multipart/byteranges" media type is not limited to byte ranges. The following example uses an "exampleunit"
1205         range unit:
1206      </p>
1207      <div id="rfc.figure.u.28"></div><pre class="text">HTTP/1.1 206 Partial Content
1208Date: Tue, 14 Nov 1995 06:25:24 GMT
1209Last-Modified: Tue, 14 July 04:58:08 GMT
1210Content-Length: 2331785
1211Content-Type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
1214Content-Type: video/example
1215Content-Range: exampleunit 1.2-4.3/25
1217...the first range...
1219Content-Type: video/example
1220Content-Range: exampleunit 11.2-14.3/25
1222...the second range
1224</pre> <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>
1225      <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;4.1</a>)
1226      </p>
1227      <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.4" title="Content-Range">Section&nbsp;4.2</a>)
1228      </p>
1229      <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)
1230         clients.
1231      </p>
1232      <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>)
1233      </p>
1234      <p id="rfc.section.B.p.5">This specification introduces a Range Unit Registry. (<a href="#range.unit.registry" title="Range Unit Registry">Section&nbsp;5.1</a>)
1235      </p>
1236      <h1 id="rfc.section.C"><a href="#rfc.section.C">C.</a>&nbsp;<a id="imported.abnf" href="#imported.abnf">Imported ABNF</a></h1>
1237      <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
1238         (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
1239         character).
1240      </p>
1241      <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>.
1242      </p>
1243      <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>:
1244      </p>
1245      <div id="rfc.figure.u.29"></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;
1246  <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;
1247</pre><p id="rfc.section.C.p.5">The rules below are defined in other parts:</p>
1248      <div id="rfc.figure.u.30"></div><pre class="inline">  <a href="#imported.abnf" class="smpl">HTTP-date</a>  = &lt;HTTP-date, defined in <a href="#Part2" id="rfc.xref.Part2.3"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content">[Part2]</cite></a>, <a href="" title="Date/Time Formats">Section</a>&gt;
1249  <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;
1250</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>
1251      <div id="rfc.figure.u.31"></div> <pre class="inline"><a href="#header.accept-ranges" class="smpl">Accept-Ranges</a> = acceptable-ranges
1253<a href="#header.content-range" class="smpl">Content-Range</a> = byte-content-range / other-content-range
1255<a href="#imported.abnf" class="smpl">HTTP-date</a> = &lt;HTTP-date, defined in [Part2], Section;
1257<a href="#header.if-range" class="smpl">If-Range</a> = entity-tag / HTTP-date
1259<a href="#imported.abnf" class="smpl">OWS</a> = &lt;OWS, defined in [Part1], Section 3.2.3&gt;
1261<a href="#header.range" class="smpl">Range</a> = byte-ranges-specifier / other-ranges-specifier
1263<a href="#header.accept-ranges" class="smpl">acceptable-ranges</a> = ( *( "," OWS ) range-unit *( OWS "," [ OWS
1264 range-unit ] ) ) / "none"
1266<a href="#header.content-range" class="smpl">byte-content-range</a> = bytes-unit SP ( byte-range-resp /
1267 unsatisfied-range )
1268<a href="#header.content-range" class="smpl">byte-range</a> = first-byte-pos "-" last-byte-pos
1269<a href="#header.content-range" class="smpl">byte-range-resp</a> = byte-range "/" ( complete-length / "*" )
1270<a href="#rule.ranges-specifier" class="smpl">byte-range-set</a> = *( "," OWS ) ( byte-range-spec /
1271 suffix-byte-range-spec ) *( OWS "," [ OWS ( byte-range-spec /
1272 suffix-byte-range-spec ) ] )
1273<a href="#rule.ranges-specifier" class="smpl">byte-range-spec</a> = first-byte-pos "-" [ last-byte-pos ]
1274<a href="#rule.ranges-specifier" class="smpl">byte-ranges-specifier</a> = bytes-unit "=" byte-range-set
1275<a href="#byte.ranges" class="smpl">bytes-unit</a> = "bytes"
1277<a href="#header.content-range" class="smpl">complete-length</a> = 1*DIGIT
1279<a href="#imported.abnf" class="smpl">entity-tag</a> = &lt;entity-tag, defined in [Part4], Section 2.3&gt;
1281<a href="#rule.ranges-specifier" class="smpl">first-byte-pos</a> = 1*DIGIT
1283<a href="#rule.ranges-specifier" class="smpl">last-byte-pos</a> = 1*DIGIT
1285<a href="#header.content-range" class="smpl">other-content-range</a> = other-range-unit SP other-range-resp
1286<a href="#header.content-range" class="smpl">other-range-resp</a> = *CHAR
1287<a href="#header.range" class="smpl">other-range-set</a> = 1*CHAR
1288<a href="#range.units.other" class="smpl">other-range-unit</a> = token
1289<a href="#header.range" class="smpl">other-ranges-specifier</a> = other-range-unit "=" other-range-set
1291<a href="#range.units" class="smpl">range-unit</a> = bytes-unit / other-range-unit
1293<a href="#rule.ranges-specifier" class="smpl">suffix-byte-range-spec</a> = "-" suffix-length
1294<a href="#rule.ranges-specifier" class="smpl">suffix-length</a> = 1*DIGIT
1296<a href="#imported.abnf" class="smpl">token</a> = &lt;token, defined in [Part1], Section 3.2.6&gt;
1298<a href="#header.content-range" class="smpl">unsatisfied-range</a> = "*/" complete-length
1299</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>
1300      <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;.
1301      </p>
1302      <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>
1303      <p id="rfc.section.E.1.p.1">Closed issues: </p>
1304      <ul>
1305         <li> &lt;<a href=""></a>&gt;: "ABNF list expansion code problem"
1306         </li>
1307         <li> &lt;<a href=""></a>&gt;: "ABNF requirements for recipients"
1308         </li>
1309         <li> &lt;<a href=""></a>&gt;: "reserve 'none' as byte range unit"
1310         </li>
1311         <li> &lt;<a href=""></a>&gt;: "note introduction of new IANA registries as normative changes"
1312         </li>
1313         <li> &lt;<a href=""></a>&gt;: "range units vs leading zeroes vs size"
1314         </li>
1315      </ul>
1316      <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>
1317      <p id="rfc.section.E.2.p.1"> </p>
1318      <ul>
1319         <li>Conformance criteria and considerations regarding error handling are now defined in Part 1.</li>
1320      </ul>
1321      <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>
1322      <p id="rfc.section.E.3.p.1">Closed issues: </p>
1323      <ul>
1324         <li> &lt;<a href=""></a>&gt;: "Security consideration: range flooding"
1325         </li>
1326         <li> &lt;<a href=""></a>&gt;: "Allowing heuristic caching for new status codes"
1327         </li>
1328         <li> &lt;<a href=""></a>&gt;: "Add limitations to Range to reduce its use as a denial-of-service tool"
1329         </li>
1330      </ul>
1331      <h2 id="rfc.section.E.4"><a href="#rfc.section.E.4">E.4</a>&nbsp;<a id="changes.since.22" href="#changes.since.22">Since draft-ietf-httpbis-p5-range-22</a></h2>
1332      <p id="rfc.section.E.4.p.1">None yet.</p>
1333      <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1>
1334      <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>
1335      </p>
1336      <div class="print2col">
1337         <ul class="ind">
1338            <li><a id="rfc.index.2" href="#rfc.index.2"><b>2</b></a><ul>
1339                  <li>206 Partial Content (status code)&nbsp;&nbsp;<a href="#rfc.iref.20"><b>4.1</b></a>, <a href="#rfc.xref.status.206.1">5.2</a>, <a href="#rfc.xref.status.206.2">B</a></li>
1340               </ul>
1341            </li>
1342            <li><a id="rfc.index.4" href="#rfc.index.4"><b>4</b></a><ul>
1343                  <li>416 Range Not Satisfiable (status code)&nbsp;&nbsp;<a href="#rfc.iref.29"><b>4.4</b></a>, <a href="#rfc.xref.status.416.1">5.2</a></li>
1344               </ul>
1345            </li>
1346            <li><a id="rfc.index.A" href="#rfc.index.A"><b>A</b></a><ul>
1347                  <li>Accept-Ranges header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept-ranges.1">2</a>, <a href="#rfc.iref.a.1"><b>2.3</b></a>, <a href="#rfc.xref.header.accept-ranges.2">5.1.2</a>, <a href="#rfc.xref.header.accept-ranges.3">5.3</a></li>
1348               </ul>
1349            </li>
1350            <li><a id="rfc.index.B" href="#rfc.index.B"><b>B</b></a><ul>
1351                  <li><em>BCP13</em>&nbsp;&nbsp;<a href="#BCP13"><b>8.2</b></a>, <a href="#rfc.xref.BCP13.1">A</a></li>
1352                  <li><em>BCP90</em>&nbsp;&nbsp;<a href="#rfc.xref.BCP90.1">5.3</a>, <a href="#BCP90"><b>8.2</b></a></li>
1353               </ul>
1354            </li>
1355            <li><a id="rfc.index.C" href="#rfc.index.C"><b>C</b></a><ul>
1356                  <li>Content-Range header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-range.1">2</a>, <a href="#rfc.iref.c.1"><b>4.2</b></a>, <a href="#rfc.xref.header.content-range.2">4.4</a>, <a href="#rfc.xref.header.content-range.3">5.3</a>, <a href="#rfc.xref.header.content-range.4">B</a></li>
1357               </ul>
1358            </li>
1359            <li><a id="rfc.index.G" href="#rfc.index.G"><b>G</b></a><ul>
1360                  <li><tt>Grammar</tt>&nbsp;&nbsp;
1361                     <ul>
1362                        <li><tt>Accept-Ranges</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.14"><b>2.3</b></a></li>
1363                        <li><tt>acceptable-ranges</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.15"><b>2.3</b></a></li>
1364                        <li><tt>byte-content-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.19"><b>4.2</b></a></li>
1365                        <li><tt>byte-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.21"><b>4.2</b></a></li>
1366                        <li><tt>byte-range-resp</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.20"><b>4.2</b></a></li>
1367                        <li><tt>byte-range-set</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.7"><b>2.1</b></a></li>
1368                        <li><tt>byte-range-spec</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.8"><b>2.1</b></a></li>
1369                        <li><tt>byte-ranges-specifier</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.6"><b>2.1</b></a></li>
1370                        <li><tt>bytes-unit</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.2">2</a>, <a href="#rfc.iref.g.4"><b>2.1</b></a></li>
1371                        <li><tt>complete-length</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.25"><b>4.2</b></a></li>
1372                        <li><tt>Content-Range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.18"><b>4.2</b></a></li>
1373                        <li><tt>first-byte-pos</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.9"><b>2.1</b></a></li>
1374                        <li><tt>If-Range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.17"><b>3.2</b></a></li>
1375                        <li><tt>last-byte-pos</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.10"><b>2.1</b></a></li>
1376                        <li><tt>other-content-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.23"><b>4.2</b></a></li>
1377                        <li><tt>other-range-resp</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.24"><b>4.2</b></a></li>
1378                        <li><tt>other-range-unit</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.3">2</a>, <a href="#rfc.iref.g.13"><b>2.2</b></a></li>
1379                        <li><tt>Range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.16"><b>3.1</b></a></li>
1380                        <li><tt>range-unit</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.1"><b>2</b></a></li>
1381                        <li><tt>ranges-specifier</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.5"><b>2.1</b></a></li>
1382                        <li><tt>suffix-byte-range-spec</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.11"><b>2.1</b></a></li>
1383                        <li><tt>suffix-length</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.12"><b>2.1</b></a></li>
1384                        <li><tt>unsatisfied-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.22"><b>4.2</b></a></li>
1385                     </ul>
1386                  </li>
1387               </ul>
1388            </li>
1389            <li><a id="rfc.index.I" href="#rfc.index.I"><b>I</b></a><ul>
1390                  <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">5.3</a></li>
1391               </ul>
1392            </li>
1393            <li><a id="rfc.index.M" href="#rfc.index.M"><b>M</b></a><ul>
1394                  <li>Media Type&nbsp;&nbsp;
1395                     <ul>
1396                        <li>multipart/byteranges&nbsp;&nbsp;<a href="#rfc.iref.m.1"><b>A</b></a></li>
1397                        <li>multipart/x-byteranges&nbsp;&nbsp;<a href="#rfc.iref.m.4">A</a></li>
1398                     </ul>
1399                  </li>
1400                  <li>multipart/byteranges Media Type&nbsp;&nbsp;<a href="#rfc.iref.m.2"><b>A</b></a></li>
1401                  <li>multipart/x-byteranges Media Type&nbsp;&nbsp;<a href="#rfc.iref.m.3">A</a></li>
1402               </ul>
1403            </li>
1404            <li><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul>
1405                  <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>
1406                        <li><em>Section 1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.2">1.2</a></li>
1407                        <li><em>Section 2.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1.1</a></li>
1408                        <li><em>Section 3.2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.6">C</a></li>
1409                        <li><em>Section 3.2.6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.7">C</a></li>
1410                        <li><em>Section 9</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.4">7</a></li>
1411                     </ul>
1412                  </li>
1413                  <li><em>Part2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.1">2.1</a>, <a href="#rfc.xref.Part2.2">6</a>, <a href="#Part2"><b>8.1</b></a>, <a href="#rfc.xref.Part2.3">C</a><ul>
1414                        <li><em>Section 3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.1">2.1</a></li>
1415                        <li><em>Section</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.3">C</a></li>
1416                     </ul>
1417                  </li>
1418                  <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">4.3</a>, <a href="#rfc.xref.Part4.5">4.3</a>, <a href="#Part4"><b>8.1</b></a>, <a href="#rfc.xref.Part4.6">C</a><ul>
1419                        <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">4.3</a></li>
1420                        <li><em>Section 2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.4">4.3</a>, <a href="#rfc.xref.Part4.6">C</a></li>
1421                     </ul>
1422                  </li>
1423                  <li><em>Part6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">4.1</a>, <a href="#Part6"><b>8.1</b></a><ul>
1424                        <li><em>Section 4.1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">4.1</a></li>
1425                     </ul>
1426                  </li>
1427               </ul>
1428            </li>
1429            <li><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul>
1430                  <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">4.1</a>, <a href="#rfc.xref.header.range.3">4.4</a>, <a href="#rfc.xref.header.range.4">5.3</a></li>
1431                  <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>
1432                        <li><em>Section 5.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2046.1">A</a></li>
1433                     </ul>
1434                  </li>
1435                  <li><em>RFC2119</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2119.1">1.1</a>, <a href="#RFC2119"><b>8.1</b></a></li>
1436                  <li><em>RFC2616</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.1">1</a>, <a href="#RFC2616"><b>8.2</b></a></li>
1437                  <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>
1438                        <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5226.1">5.1.1</a></li>
1439                     </ul>
1440                  </li>
1441                  <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>
1442                        <li><em>Appendix B.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5234.2">C</a></li>
1443                     </ul>
1444                  </li>
1445               </ul>
1446            </li>
1447         </ul>
1448      </div>
1449   </body>
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