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370       content: "Reschke";
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391</style><link rel="Contents" href="#rfc.toc">
392      <link rel="Author" href="#rfc.authors">
393      <link rel="Copyright" href="#rfc.copyrightnotice">
394      <link rel="Index" href="#rfc.index">
395      <link rel="Chapter" title="1 Introduction" href="#rfc.section.1">
396      <link rel="Chapter" title="2 Notational Conventions" href="#rfc.section.2">
397      <link rel="Chapter" title="3 Header Field Definition" href="#rfc.section.3">
398      <link rel="Chapter" title="4 Examples" href="#rfc.section.4">
399      <link rel="Chapter" title="5 Internationalization Considerations" href="#rfc.section.5">
400      <link rel="Chapter" title="6 Security Considerations" href="#rfc.section.6">
401      <link rel="Chapter" title="7 IANA Considerations" href="#rfc.section.7">
402      <link rel="Chapter" title="8 Acknowledgements" href="#rfc.section.8">
403      <link rel="Chapter" href="#rfc.section.9" title="9 References">
404      <link rel="Appendix" title="A Changes from the RFC 2616 Definition" href="#rfc.section.A">
405      <link rel="Appendix" title="B Differences compared to RFC 2183" href="#rfc.section.B">
406      <link rel="Appendix" title="C Alternative Approaches to Internationalization" href="#rfc.section.C">
407      <link rel="Appendix" title="D Change Log (to be removed by RFC Editor before publication)" href="#rfc.section.D">
408      <meta name="generator" content="http://greenbytes.de/tech/webdav/rfc2629.xslt, Revision 1.640, 2014/06/13 12:42:58, XSLT vendor: SAXON 8.9 from Saxonica http://www.saxonica.com/">
409      <link rel="schema.dct" href="http://purl.org/dc/terms/">
410      <meta name="dct.creator" content="Reschke, J. F.">
411      <meta name="dct.identifier" content="urn:ietf:id:draft-ietf-httpbis-content-disp-01">
412      <meta name="dct.issued" scheme="ISO8601" content="2010-09-16">
413      <meta name="dct.abstract" content="HTTP/1.1 defines the Content-Disposition response header field, but points out that it is not part of the HTTP/1.1 Standard. This specification takes over the definition and registration of Content-Disposition, as used in HTTP, and clarifies internationalization aspects.">
414      <meta name="description" content="HTTP/1.1 defines the Content-Disposition response header field, but points out that it is not part of the HTTP/1.1 Standard. This specification takes over the definition and registration of Content-Disposition, as used in HTTP, and clarifies internationalization aspects.">
415   </head>
416   <body>
417      <table class="header">
418         <tbody>
419            <tr>
420               <td class="left">HTTPbis Working Group</td>
421               <td class="right">J. Reschke</td>
422            </tr>
423            <tr>
424               <td class="left">Internet-Draft</td>
425               <td class="right">greenbytes</td>
426            </tr>
427            <tr>
428               <td class="left">Updates: <a href="https://tools.ietf.org/html/rfc2616">2616</a> (if approved)
429               </td>
430               <td class="right">September 16, 2010</td>
431            </tr>
432            <tr>
433               <td class="left">Intended status: Standards Track</td>
434               <td class="right"></td>
435            </tr>
436            <tr>
437               <td class="left">Expires: March 20, 2011</td>
438               <td class="right"></td>
439            </tr>
440         </tbody>
441      </table>
442      <p class="title">Use of the Content-Disposition&nbsp;Header&nbsp;Field in the Hypertext&nbsp;Transfer&nbsp;Protocol&nbsp;(HTTP)<br><span class="filename">draft-ietf-httpbis-content-disp-01</span></p>
443      <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
444      <p>HTTP/1.1 defines the Content-Disposition response header field, but points out that it is not part of the HTTP/1.1 Standard.
445         This specification takes over the definition and registration of Content-Disposition, as used in HTTP, and clarifies internationalization
446         aspects.
447      </p>
448      <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor before publication)</a></h1>
449      <p>This specification is expected to replace the definition of Content-Disposition in the HTTP/1.1 specification, as currently
450         revised by the IETF HTTPbis working group. See also &lt;<a href="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/123">http://trac.tools.ietf.org/wg/httpbis/trac/ticket/123</a>&gt;.
451      </p>
452      <p>Discussion of this draft should take place on the HTTPBIS working group mailing list (ietf-http-wg@w3.org). The current issues
453         list is at &lt;<a href="http://trac.tools.ietf.org/wg/httpbis/trac/query?component=content-disp">http://trac.tools.ietf.org/wg/httpbis/trac/query?component=content-disp</a>&gt; and related documents (including fancy diffs) can be found at &lt;<a href="http://tools.ietf.org/wg/httpbis/">http://tools.ietf.org/wg/httpbis/</a>&gt;.
454      </p>
455      <p>The changes in this draft are summarized in <a href="#changes.since.00" title="Since draft-ietf-httpbis-content-disp-00">Appendix&nbsp;D.5</a>.
456      </p>
457      <div id="rfc.status">
458         <h1><a href="#rfc.status">Status of This Memo</a></h1>
459         <p>This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.</p>
460         <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute
461            working documents as Internet-Drafts. The list of current Internet-Drafts is at <a href="http://datatracker.ietf.org/drafts/current/">http://datatracker.ietf.org/drafts/current/</a>.
462         </p>
463         <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
464            documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
465            in progress”.
466         </p>
467         <p>This Internet-Draft will expire on March 20, 2011.</p>
468      </div>
469      <div id="rfc.copyrightnotice">
470         <h1><a href="#rfc.copyrightnotice">Copyright Notice</a></h1>
471         <p>Copyright © 2010 IETF Trust and the persons identified as the document authors. All rights reserved.</p>
472         <p>This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights
473            and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License
474            text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified
475            BSD License.
476         </p>
477      </div>
478      <hr class="noprint">
479      <h1 class="np" id="rfc.toc"><a href="#rfc.toc">Table of Contents</a></h1>
480      <ul class="toc">
481         <li><a href="#rfc.section.1">1.</a>&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a></li>
482         <li><a href="#rfc.section.2">2.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2">Notational Conventions</a></li>
483         <li><a href="#rfc.section.3">3.</a>&nbsp;&nbsp;&nbsp;<a href="#header.field.definition">Header Field Definition</a><ul>
484               <li><a href="#rfc.section.3.1">3.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.3.1">Grammar</a></li>
485               <li><a href="#rfc.section.3.2">3.2</a>&nbsp;&nbsp;&nbsp;<a href="#disposition.type">Disposition Type</a></li>
486               <li><a href="#rfc.section.3.3">3.3</a>&nbsp;&nbsp;&nbsp;<a href="#disposition.parameter.filename">Disposition Parameter: 'Filename'</a></li>
487               <li><a href="#rfc.section.3.4">3.4</a>&nbsp;&nbsp;&nbsp;<a href="#disposition.parameter.extensions">Disposition Parameter: Extensions</a></li>
488               <li><a href="#rfc.section.3.5">3.5</a>&nbsp;&nbsp;&nbsp;<a href="#extensibility">Extensibility</a></li>
489            </ul>
490         </li>
491         <li><a href="#rfc.section.4">4.</a>&nbsp;&nbsp;&nbsp;<a href="#examples">Examples</a></li>
492         <li><a href="#rfc.section.5">5.</a>&nbsp;&nbsp;&nbsp;<a href="#i18n">Internationalization Considerations</a></li>
493         <li><a href="#rfc.section.6">6.</a>&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a></li>
494         <li><a href="#rfc.section.7">7.</a>&nbsp;&nbsp;&nbsp;<a href="#iana.considerations">IANA Considerations</a><ul>
495               <li><a href="#rfc.section.7.1">7.1</a>&nbsp;&nbsp;&nbsp;<a href="#registry">Registry for Disposition Values and Parameter</a></li>
496               <li><a href="#rfc.section.7.2">7.2</a>&nbsp;&nbsp;&nbsp;<a href="#header.field.registration">Header Field Registration</a></li>
497            </ul>
498         </li>
499         <li><a href="#rfc.section.8">8.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.8">Acknowledgements</a></li>
500         <li><a href="#rfc.section.9">9.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
501               <li><a href="#rfc.section.9.1">9.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
502               <li><a href="#rfc.section.9.2">9.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
503            </ul>
504         </li>
505         <li><a href="#rfc.section.A">A.</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc2616">Changes from the RFC 2616 Definition</a></li>
506         <li><a href="#rfc.section.B">B.</a>&nbsp;&nbsp;&nbsp;<a href="#diffs.compared.to.rfc2183">Differences compared to RFC 2183</a></li>
507         <li><a href="#rfc.section.C">C.</a>&nbsp;&nbsp;&nbsp;<a href="#alternatives">Alternative Approaches to Internationalization</a><ul>
508               <li><a href="#rfc.section.C.1">C.1</a>&nbsp;&nbsp;&nbsp;<a href="#alternatives.rfc2047">RFC 2047 Encoding</a></li>
509               <li><a href="#rfc.section.C.2">C.2</a>&nbsp;&nbsp;&nbsp;<a href="#alternatives.percent">Percent Encoding</a></li>
510               <li><a href="#rfc.section.C.3">C.3</a>&nbsp;&nbsp;&nbsp;<a href="#alternatives.sniff">Encoding Sniffing</a></li>
511               <li><a href="#rfc.section.C.4">C.4</a>&nbsp;&nbsp;&nbsp;<a href="#alternatives.implementations">Implementations (to be removed by RFC Editor before publication)</a></li>
512            </ul>
513         </li>
514         <li><a href="#rfc.section.D">D.</a>&nbsp;&nbsp;&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a><ul>
515               <li><a href="#rfc.section.D.1">D.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.D.1">Since draft-reschke-rfc2183-in-http-00</a></li>
516               <li><a href="#rfc.section.D.2">D.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.D.2">Since draft-reschke-rfc2183-in-http-01</a></li>
517               <li><a href="#rfc.section.D.3">D.3</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.D.3">Since draft-reschke-rfc2183-in-http-02</a></li>
518               <li><a href="#rfc.section.D.4">D.4</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.D.4">Since draft-reschke-rfc2183-in-http-03</a></li>
519               <li><a href="#rfc.section.D.5">D.5</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.00">Since draft-ietf-httpbis-content-disp-00</a></li>
520            </ul>
521         </li>
522         <li><a href="#rfc.index">Index</a></li>
523         <li><a href="#rfc.authors">Author's Address</a></li>
524      </ul>
525      <div id="introduction">
526         <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a href="#introduction">Introduction</a></h1>
527         <p id="rfc.section.1.p.1">HTTP/1.1 defines the Content-Disposition response header field in <a href="https://tools.ietf.org/html/rfc2616#section-19.5.1">Section 19.5.1</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, but points out that it is not part of the HTTP/1.1 Standard (<a href="https://tools.ietf.org/html/rfc2616#section-15.5" id="rfc.xref.RFC2616.2">Section 15.5</a>):
528         </p>
529         <blockquote id="rfc.section.1.p.2" cite="http://tools.ietf.org/html/rfc2616#section-15.5">
530            <p>Content-Disposition is not part of the HTTP standard, but since it is widely implemented, we are documenting its use and risks
531               for implementers.
532            </p>
533         </blockquote>
534         <p id="rfc.section.1.p.3">This specification takes over the definition and registration of Content-Disposition, as used in HTTP. Based on interoperability
535            testing with existing User Agents, it fully defines a profile of the features defined in the Multipurpose Internet Mail Extensions
536            (MIME) variant (<a href="#RFC2183" id="rfc.xref.RFC2183.1"><cite title="Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field">[RFC2183]</cite></a>) of the header field, and also clarifies internationalization aspects.
537         </p>
538      </div>
539      <div>
540         <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;Notational Conventions
541         </h1>
542         <p id="rfc.section.2.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
543            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>.
544         </p>
545         <p id="rfc.section.2.p.2">This specification uses the augmented BNF notation defined in <a href="https://tools.ietf.org/html/rfc2616#section-2.1">Section 2.1</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, including its rules for linear whitespace (LWS).
546         </p>
547      </div>
548      <div id="header.field.definition">
549         <div id="rfc.iref.h.1"></div>
550         <div id="rfc.iref.c.1"></div>
551         <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a href="#header.field.definition">Header Field Definition</a></h1>
552         <p id="rfc.section.3.p.1">The Content-Disposition response header field is used to convey additional information about how to process the response payload,
553            and also can be used to attach additional metadata, such as the filename.
554         </p>
555         <div>
556            <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;Grammar
557            </h2>
558            <div id="rfc.figure.u.1"></div><pre class="inline">  content-disposition = "Content-Disposition" ":"
559                         disposition-type *( ";" disposition-parm )
560
561  disposition-type    = "inline" | "attachment" | disp-ext-type
562                      ; case-insensitive
563  disp-ext-type       = token
564
565  disposition-parm    = filename-parm | disp-ext-parm
566
567  filename-parm       = "filename" "=" value
568                      | "filename*" "=" ext-value
569 
570  disp-ext-parm       = token "=" value
571                      | ext-token "=" ext-value
572  ext-token           = &lt;the characters in token, followed by "*"&gt;
573</pre><div id="rfc.figure.u.2"></div>
574            <p>Defined in <a href="#RFC2616" id="rfc.xref.RFC2616.4"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>:
575            </p><pre class="inline">  token       = &lt;token, defined in <a href="#RFC2616" id="rfc.xref.RFC2616.5"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, <a href="https://tools.ietf.org/html/rfc2616#section-2.2">Section 2.2</a>&gt;
576  value       = &lt;value, defined in <a href="#RFC2616" id="rfc.xref.RFC2616.6"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, <a href="https://tools.ietf.org/html/rfc2616#section-3.6">Section 3.6</a>&gt;
577</pre><div id="rfc.figure.u.3"></div>
578            <p>Defined in <a href="#RFC5987" id="rfc.xref.RFC5987.1"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a>:
579            </p><pre class="inline">  ext-value   = &lt;ext-value, defined in <a href="#RFC5987" id="rfc.xref.RFC5987.2"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a>, <a href="https://tools.ietf.org/html/rfc5987#section-3.2">Section 3.2</a>&gt;
580</pre></div>
581         <div id="disposition.type">
582            <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a href="#disposition.type">Disposition Type</a></h2>
583            <p id="rfc.section.3.2.p.1">If the disposition type matches "attachment" (case-insensitively), this indicates that the user agent should not display the
584               response, but directly enter a "save as..." dialog.
585            </p>
586            <p id="rfc.section.3.2.p.2">On the other hand, if it matches "inline" (case-insensitively), this implies default processing.</p>
587            <p id="rfc.section.3.2.p.3">Unknown or unhandled disposition types <em class="bcp14">SHOULD</em> be handled the same way as "attachment" (see also <a href="#RFC2183" id="rfc.xref.RFC2183.2"><cite title="Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field">[RFC2183]</cite></a>, <a href="https://tools.ietf.org/html/rfc2183#section-2.8">Section 2.8</a>).
588            </p>
589         </div>
590         <div id="disposition.parameter.filename">
591            <h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a>&nbsp;<a href="#disposition.parameter.filename">Disposition Parameter: 'Filename'</a></h2>
592            <p id="rfc.section.3.3.p.1">The parameters "filename" and "filename*", to be matched case-insensitively, provide information on how to construct a filename
593               for storing the message payload.
594            </p>
595            <p id="rfc.section.3.3.p.2">Depending on the disposition type, this information might be used right away (in the "save as..." interaction caused for the
596               "attachment" disposition type), or later on (for instance, when the user decides to save the contents of the current page
597               being displayed).
598            </p>
599            <p id="rfc.section.3.3.p.3">The parameters "filename" and "filename*" differ only in that "filename*" uses the encoding defined in <a href="#RFC5987" id="rfc.xref.RFC5987.3"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a>, allowing the use of characters not present in the ISO-8859-1 character set (<a href="#ISO-8859-1" id="rfc.xref.ISO-8859-1.1"><cite title="Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1">[ISO-8859-1]</cite></a>).
600            </p>
601            <p id="rfc.section.3.3.p.4">Many user agent implementations predating this specification do not understand the "filename*" parameter. Therefore, when
602               both "filename" and "filename*" are present in a single header field value, recipients <em class="bcp14">SHOULD</em> pick "filename*" and ignore "filename". This way, senders can avoid special-casing specific user agents by sending both the
603               more expressive "filename*" parameter, and the "filename" parameter as fallback for legacy recipients (see <a href="#examples" title="Examples">Section&nbsp;4</a> for an example).
604            </p>
605            <p id="rfc.section.3.3.p.5">It is essential that user agents treat the specified filename as advisory only, thus be very careful in extracting the desired
606               information. In particular:
607            </p>
608            <ul>
609               <li>
610                  <p>When the value contains path separator characters, all but the last segment <em class="bcp14">SHOULD</em> be ignored. This prevents unintentional overwriting of well-known file system location (such as "/etc/passwd").
611                  </p>
612               </li>
613               <li>
614                  <p>Many platforms do not use Internet Media Types (<a href="#RFC2046" id="rfc.xref.RFC2046.1"><cite title="Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types">[RFC2046]</cite></a>) to hold type information in the file system, but rely on filename extensions instead. Trusting the server-provided file
615                     extension could introduce a privilege escalation when later on the file is opened locally (consider ".exe"). Thus, recipients
616                     need to ensure that a file extension is used that is safe, optimally matching the media type of the received payload.
617                  </p>
618               </li>
619               <li>
620                  <p>Other aspects recipients need to be aware of are names that have a special meaning in the file system or in shell commands,
621                     such as "." and "..", "~", "|", and also device names.
622                  </p>
623               </li>
624            </ul>
625         </div>
626         <div id="disposition.parameter.extensions">
627            <h2 id="rfc.section.3.4"><a href="#rfc.section.3.4">3.4</a>&nbsp;<a href="#disposition.parameter.extensions">Disposition Parameter: Extensions</a></h2>
628            <p id="rfc.section.3.4.p.1">To enable future extensions, unknown parameters <em class="bcp14">SHOULD</em> be ignored (see also <a href="#RFC2183" id="rfc.xref.RFC2183.3"><cite title="Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field">[RFC2183]</cite></a>, <a href="https://tools.ietf.org/html/rfc2183#section-2.8">Section 2.8</a>).
629            </p>
630         </div>
631         <div id="extensibility">
632            <h2 id="rfc.section.3.5"><a href="#rfc.section.3.5">3.5</a>&nbsp;<a href="#extensibility">Extensibility</a></h2>
633            <p id="rfc.section.3.5.p.1">Note that <a href="https://tools.ietf.org/html/rfc2183#section-9">Section 9</a> of <a href="#RFC2183" id="rfc.xref.RFC2183.4"><cite title="Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field">[RFC2183]</cite></a> defines IANA registries both for disposition types and disposition parameters. This registry is shared by different protocols
634               using Content-Disposition, such as MIME and HTTP. Therefore, not all registered values may make sense in the context of HTTP.
635            </p>
636         </div>
637      </div>
638      <div id="examples">
639         <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a href="#examples">Examples</a></h1>
640         <div id="rfc.figure.u.4"></div>
641         <p>Direct UA to show "save as" dialog, with a filename of "example.html":</p><pre class="text">Content-Disposition: Attachment; filename=example.html
642</pre><div id="rfc.figure.u.5"></div>
643         <p>Direct UA to behave as if the Content-Disposition header field wasn't present, but to remember the filename "example.html"
644            for a subsequent save operation:
645         </p><pre class="text">Content-Disposition: INLINE; FILENAME= "example.html"
646</pre><div id="rfc.figure.u.6"></div>
647         <p>Direct UA to show "save as" dialog, with a filename of "an example":</p><pre class="text">Content-Disposition: Attachment; Filename*=UTF-8'<b>en</b>'an<b>%20</b>example
648</pre><p>Note that this example uses the extended encoding defined in <a href="#RFC5987" id="rfc.xref.RFC5987.4"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a> to specify that the natural language of the filename is English, and also to encode the space character which is not allowed
649            in the token production.
650         </p>
651         <div id="rfc.figure.u.7"></div>
652         <p>Direct UA to show "save as" dialog, with a filename containing the Unicode character U+20AC (EURO SIGN):</p><pre class="text">Content-Disposition: attachment;
653                     filename*= UTF-8''<b>%e2%82%ac</b>%20rates
654</pre><p>Here, the encoding defined in <a href="#RFC5987" id="rfc.xref.RFC5987.5"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a> is also used to encode the non-ISO-8859-1 character.
655         </p>
656         <div id="rfc.figure.u.8"></div>
657         <p>Same as above, but adding the "filename" parameter for compatibility with user agents not implementing RFC 5987:</p><pre class="text">Content-Disposition: attachment;
658                     filename="EURO rates";
659                     filename*=utf-8''<b>%e2%82%ac</b>%20rates
660</pre><p>Note: as of September 2010, those user agents that do not support the RFC 5987 encoding ignore "filename*" when it occurs
661            after "filename". Unfortunately, some user agents that do support RFC 5987 do pick the "filename" rather than the "filename*"
662            parameter when it occurs first; it is expected that this situation is going to improve soon.
663         </p>
664      </div>
665      <div id="i18n">
666         <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a href="#i18n">Internationalization Considerations</a></h1>
667         <p id="rfc.section.5.p.1">The "filename*" parameter (<a href="#disposition.parameter.filename" title="Disposition Parameter: 'Filename'">Section&nbsp;3.3</a>), using the encoding defined in <a href="#RFC5987" id="rfc.xref.RFC5987.6"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a>, allows the server to transmit characters outside the ISO-8859-1 character set, and also to optionally specify the language
668            in use.
669         </p>
670         <p id="rfc.section.5.p.2">Future parameters might also require internationalization, in which case the same encoding can be used.</p>
671      </div>
672      <div id="security.considerations">
673         <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a href="#security.considerations">Security Considerations</a></h1>
674         <p id="rfc.section.6.p.1">Using server-supplied information for constructing local filenames introduces many risks. These are summarized in <a href="#disposition.parameter.filename" title="Disposition Parameter: 'Filename'">Section&nbsp;3.3</a>.
675         </p>
676         <p id="rfc.section.6.p.2">Furthermore, implementers also ought to be aware of the Security Considerations applying to HTTP (see <a href="https://tools.ietf.org/html/rfc2616#section-15">Section 15</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.7"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>), and also the parameter encoding defined in <a href="#RFC5987" id="rfc.xref.RFC5987.7"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a> (see <a href="https://tools.ietf.org/html/rfc5987#section-5" id="rfc.xref.RFC5987.8">Section 5</a>).
677         </p>
678      </div>
679      <div id="iana.considerations">
680         <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a href="#iana.considerations">IANA Considerations</a></h1>
681         <div id="registry">
682            <h2 id="rfc.section.7.1"><a href="#rfc.section.7.1">7.1</a>&nbsp;<a href="#registry">Registry for Disposition Values and Parameter</a></h2>
683            <p id="rfc.section.7.1.p.1">This specification does not introduce any changes to the registration procedures for disposition values and parameters that
684               are defined in <a href="https://tools.ietf.org/html/rfc2183#section-9">Section 9</a> of <a href="#RFC2183" id="rfc.xref.RFC2183.5"><cite title="Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field">[RFC2183]</cite></a>.
685            </p>
686         </div>
687         <div id="header.field.registration">
688            <h2 id="rfc.section.7.2"><a href="#rfc.section.7.2">7.2</a>&nbsp;<a href="#header.field.registration">Header Field Registration</a></h2>
689            <p id="rfc.section.7.2.p.1">This document updates the definition of the Content-Disposition HTTP header field in the permanent HTTP header field registry
690               (see <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>).
691            </p>
692            <p id="rfc.section.7.2.p.2"></p>
693            <dl>
694               <dt>Header field name:</dt>
695               <dd>Content-Disposition</dd>
696               <dt>Applicable protocol:</dt>
697               <dd>http</dd>
698               <dt>Status:</dt>
699               <dd>standard</dd>
700               <dt>Author/Change controller:</dt>
701               <dd>IETF</dd>
702               <dt>Specification document:</dt>
703               <dd>this specification (<a href="#header.field.definition" id="rfc.xref.header.field.definition.1" title="Header Field Definition">Section&nbsp;3</a>)
704               </dd>
705            </dl>
706         </div>
707      </div>
708      <div>
709         <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a>&nbsp;Acknowledgements
710         </h1>
711         <p id="rfc.section.8.p.1">Thanks to Rolf Eike Beer, Bjoern Hoehrmann, Alfred Hoenes, Roar Lauritzsen, and Henrik Nordstrom for their valuable feedback.</p>
712      </div>
713      <h1 id="rfc.references"><a id="rfc.section.9" href="#rfc.section.9">9.</a> References
714      </h1>
715      <h2 id="rfc.references.1"><a href="#rfc.section.9.1" id="rfc.section.9.1">9.1</a> Normative References
716      </h2>
717      <table>
718         <tr>
719            <td class="reference"><b id="ISO-8859-1">[ISO-8859-1]</b></td>
720            <td class="top">International Organization for Standardization, “Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1”, ISO/IEC&nbsp;8859-1:1998, 1998.</td>
721         </tr>
722         <tr>
723            <td class="reference"><b id="RFC2119">[RFC2119]</b></td>
724            <td class="top"><a href="mailto:sob@harvard.edu" title="Harvard University">Bradner, S.</a>, “<a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>”, BCP&nbsp;14, RFC&nbsp;2119, March&nbsp;1997.
725            </td>
726         </tr>
727         <tr>
728            <td class="reference"><b id="RFC2616">[RFC2616]</b></td>
729            <td class="top"><a href="mailto:fielding@ics.uci.edu" title="University of California, Irvine">Fielding, R.</a>, <a href="mailto:jg@w3.org" title="W3C">Gettys, J.</a>, <a href="mailto:mogul@wrl.dec.com" title="Compaq Computer Corporation">Mogul, J.</a>, <a href="mailto:frystyk@w3.org" title="MIT Laboratory for Computer Science">Frystyk, H.</a>, <a href="mailto:masinter@parc.xerox.com" title="Xerox Corporation">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, and <a href="mailto:timbl@w3.org" title="W3C">T. Berners-Lee</a>, “<a href="https://tools.ietf.org/html/rfc2616">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2616, June&nbsp;1999.
730            </td>
731         </tr>
732         <tr>
733            <td class="reference"><b id="RFC5987">[RFC5987]</b></td>
734            <td class="top"><a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">Reschke, J.</a>, “<a href="https://tools.ietf.org/html/rfc5987">Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</a>”, RFC&nbsp;5987, August&nbsp;2010.
735            </td>
736         </tr>
737      </table>
738      <h2 id="rfc.references.2"><a href="#rfc.section.9.2" id="rfc.section.9.2">9.2</a> Informative References
739      </h2>
740      <table>
741         <tr>
742            <td class="reference"><b id="RFC2046">[RFC2046]</b></td>
743            <td class="top"><a href="mailto:ned@innosoft.com" title="Innosoft International, Inc.">Freed, N.</a> and <a href="mailto:nsb@nsb.fv.com" title="First Virtual Holdings">N. Borenstein</a>, “<a href="https://tools.ietf.org/html/rfc2046">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</a>”, RFC&nbsp;2046, November&nbsp;1996.
744            </td>
745         </tr>
746         <tr>
747            <td class="reference"><b id="RFC2047">[RFC2047]</b></td>
748            <td class="top"><a href="mailto:moore@cs.utk.edu" title="University of Tennessee">Moore, K.</a>, “<a href="https://tools.ietf.org/html/rfc2047">MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text</a>”, RFC&nbsp;2047, November&nbsp;1996.
749            </td>
750         </tr>
751         <tr>
752            <td class="reference"><b id="RFC2183">[RFC2183]</b></td>
753            <td class="top"><a href="mailto:rens@century.com" title="New Century Systems">Troost, R.</a>, <a href="mailto:sdorner@qualcomm.com" title="QUALCOMM Incorporated">Dorner, S.</a>, and <a href="mailto:moore@cs.utk.edu" title="Department of Computer Science">K. Moore</a>, “<a href="https://tools.ietf.org/html/rfc2183">Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field</a>”, RFC&nbsp;2183, August&nbsp;1997.
754            </td>
755         </tr>
756         <tr>
757            <td class="reference"><b id="RFC2231">[RFC2231]</b></td>
758            <td class="top"><a href="mailto:ned.freed@innosoft.com" title="Innosoft International, Inc.">Freed, N.</a> and <a href="mailto:moore@cs.utk.edu" title="University of Tennessee">K. Moore</a>, “<a href="https://tools.ietf.org/html/rfc2231">MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations</a>”, RFC&nbsp;2231, November&nbsp;1997.
759            </td>
760         </tr>
761         <tr>
762            <td class="reference"><b id="RFC3629">[RFC3629]</b></td>
763            <td class="top"><a href="mailto:fyergeau@alis.com" title="Alis Technologies">Yergeau, F.</a>, “<a href="https://tools.ietf.org/html/rfc3629">UTF-8, a transformation format of ISO 10646</a>”, STD&nbsp;63, RFC&nbsp;3629, November&nbsp;2003.
764            </td>
765         </tr>
766         <tr>
767            <td class="reference"><b id="RFC3864">[RFC3864]</b></td>
768            <td class="top"><a href="mailto:GK-IETF@ninebynine.org" title="Nine by Nine">Klyne, G.</a>, <a href="mailto:mnot@pobox.com" title="BEA Systems">Nottingham, M.</a>, and <a href="mailto:JeffMogul@acm.org" title="HP Labs">J. Mogul</a>, “<a href="https://tools.ietf.org/html/rfc3864">Registration Procedures for Message Header Fields</a>”, BCP&nbsp;90, RFC&nbsp;3864, September&nbsp;2004.
769            </td>
770         </tr>
771         <tr>
772            <td class="reference"><b id="RFC3986">[RFC3986]</b></td>
773            <td class="top"><a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R.</a>, and <a href="mailto:LMM@acm.org" title="Adobe Systems Incorporated">L. Masinter</a>, “<a href="https://tools.ietf.org/html/rfc3986">Uniform Resource Identifier (URI): Generic Syntax</a>”, STD&nbsp;66, RFC&nbsp;3986, January&nbsp;2005.
774            </td>
775         </tr>
776      </table>
777      <div id="changes.from.rfc2616">
778         <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;<a href="#changes.from.rfc2616">Changes from the RFC 2616 Definition</a></h1>
779         <p id="rfc.section.A.p.1">Compared to <a href="https://tools.ietf.org/html/rfc2616#section-19.5.1">Section 19.5.1</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.8"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, the following normative changes reflecting actual implementations have been made:
780         </p>
781         <ul>
782            <li>According to RFC 2616, the disposition type "attachment" only applies to content of type "application/octet-stream". This
783               restriction has been removed, because user agents in practice do not check the content type, and it also discourages properly
784               declaring the media type.
785            </li>
786            <li>RFC 2616 only allows "quoted-string" for the filename parameter. This would be an exceptional parameter syntax, and also doesn't
787               reflect actual use.
788            </li>
789            <li>The definition for the disposition type "inline" (<a href="#RFC2183" id="rfc.xref.RFC2183.6"><cite title="Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field">[RFC2183]</cite></a>, <a href="https://tools.ietf.org/html/rfc2183#section-2.1">Section 2.1</a>) has been re-added with a suggestion for its processing.
790            </li>
791            <li>This specification requires support for the extended parameter encoding defined in <a href="#RFC5987" id="rfc.xref.RFC5987.9"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a>.
792            </li>
793         </ul>
794      </div>
795      <div id="diffs.compared.to.rfc2183">
796         <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;<a href="#diffs.compared.to.rfc2183">Differences compared to RFC 2183</a></h1>
797         <p id="rfc.section.B.p.1"><a href="https://tools.ietf.org/html/rfc2183#section-2">Section 2</a> of <a href="#RFC2183" id="rfc.xref.RFC2183.7"><cite title="Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field">[RFC2183]</cite></a> defines several additional disposition parameters: "creation-date", "modification-date", "quoted-date-time", and "size". These
798            do not appear to be implemented by any user agent, thus have been omitted from this specification.
799         </p>
800      </div>
801      <div id="alternatives">
802         <h1 id="rfc.section.C"><a href="#rfc.section.C">C.</a>&nbsp;<a href="#alternatives">Alternative Approaches to Internationalization</a></h1>
803         <p id="rfc.section.C.p.1">By default, HTTP header field parameters cannot carry characters outside the ISO-8859-1 (<a href="#ISO-8859-1" id="rfc.xref.ISO-8859-1.2"><cite title="Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1">[ISO-8859-1]</cite></a>) character encoding (see <a href="#RFC2616" id="rfc.xref.RFC2616.9"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, <a href="https://tools.ietf.org/html/rfc2616#section-2.2">Section 2.2</a>). For the "filename" parameter, this of course is an unacceptable restriction.
804         </p>
805         <p id="rfc.section.C.p.2">Unfortunately, user agent implementers have not managed to come up with an interoperable approach, although the IETF Standards
806            Track specifies exactly one solution (<a href="#RFC2231" id="rfc.xref.RFC2231.1"><cite title="MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations">[RFC2231]</cite></a>, clarified and profiled for HTTP in <a href="#RFC5987" id="rfc.xref.RFC5987.10"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a>).
807         </p>
808         <p id="rfc.section.C.p.3">For completeness, the sections below describe the various approaches that have been tried, and explains how they are inferior
809            to the RFC 5987 encoding used in this specification.
810         </p>
811         <div id="alternatives.rfc2047">
812            <h2 id="rfc.section.C.1"><a href="#rfc.section.C.1">C.1</a>&nbsp;<a href="#alternatives.rfc2047">RFC 2047 Encoding</a></h2>
813            <p id="rfc.section.C.1.p.1">RFC 2047 defines an encoding mechanism for header fields, but this encoding is not supposed to be used for header field parameters
814               - see <a href="https://tools.ietf.org/html/rfc2047#section-5">Section 5</a> of <a href="#RFC2047" id="rfc.xref.RFC2047.1"><cite title="MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text">[RFC2047]</cite></a>:
815            </p>
816            <blockquote id="rfc.section.C.1.p.2" cite="http://tools.ietf.org/html/rfc2047#section-5">
817               <p>An 'encoded-word' MUST NOT appear within a 'quoted-string'.</p>
818               <p>...</p>
819               <p>An 'encoded-word' MUST NOT be used in parameter of a MIME Content-Type or Content-Disposition field, or in any structured
820                  field body except within a 'comment' or 'phrase'.
821               </p>
822            </blockquote>
823            <p id="rfc.section.C.1.p.3">In practice, some user agents implement the encoding, some do not (exposing the encoded string to the user), and some get
824               confused by it.
825            </p>
826         </div>
827         <div id="alternatives.percent">
828            <h2 id="rfc.section.C.2"><a href="#rfc.section.C.2">C.2</a>&nbsp;<a href="#alternatives.percent">Percent Encoding</a></h2>
829            <p id="rfc.section.C.2.p.1">Some user agents accept percent encoded (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="https://tools.ietf.org/html/rfc3986#section-2.1">Section 2.1</a>) sequences of characters encoded using the UTF-8 (<a href="#RFC3629" id="rfc.xref.RFC3629.1"><cite title="UTF-8, a transformation format of ISO 10646">[RFC3629]</cite></a>) character encoding.
830            </p>
831            <p id="rfc.section.C.2.p.2">In practice, this is hard to use because those user agents that do not support it will display the escaped character sequence
832               to the user.
833            </p>
834            <p id="rfc.section.C.2.p.3">Furthermore, the first user agent to implement this did choose the encoding based on local settings; thus making it very hard
835               to use in multi-lingual environments.
836            </p>
837         </div>
838         <div id="alternatives.sniff">
839            <h2 id="rfc.section.C.3"><a href="#rfc.section.C.3">C.3</a>&nbsp;<a href="#alternatives.sniff">Encoding Sniffing</a></h2>
840            <p id="rfc.section.C.3.p.1">Some user agents inspect the value (which defaults to ISO-8859-1) and switch to UTF-8 when it seems to be more likely to be
841               the correct interpretation.
842            </p>
843            <p id="rfc.section.C.3.p.2">As with the approaches above, this is not interoperable and furthermore risks misinterpreting the actual value.</p>
844         </div>
845         <div id="alternatives.implementations">
846            <h2 id="rfc.section.C.4"><a href="#rfc.section.C.4">C.4</a>&nbsp;<a href="#alternatives.implementations">Implementations (to be removed by RFC Editor before publication)</a></h2>
847            <p id="rfc.section.C.4.p.1">Unfortunately, as of September 2010, neither the encoding defined in RFCs 2231 and 5987, nor any of the alternate approaches
848               discussed above was implemented interoperably. Thus, this specification recommends the approach defined in RFC 5987, which
849               at least has the advantage of actually being specified properly.
850            </p>
851            <p id="rfc.section.C.4.p.2">The table below shows the implementation support for the various approaches:</p>
852            <div id="rfc.table.u.1">
853               <table class="tt full left" cellpadding="3" cellspacing="0">
854                  <thead>
855                     <tr>
856                        <th>User Agent</th>
857                        <th>RFC 2231/5987</th>
858                        <th>RFC 2047</th>
859                        <th>Percent Encoding</th>
860                        <th>Encoding Sniffing</th>
861                     </tr>
862                  </thead>
863                  <tbody>
864                     <tr>
865                        <td class="left">Chrome</td>
866                        <td class="left">no</td>
867                        <td class="left">yes</td>
868                        <td class="left">yes</td>
869                        <td class="left">yes</td>
870                     </tr>
871                     <tr>
872                        <td class="left">Firefox</td>
873                        <td class="left">yes (*)</td>
874                        <td class="left">yes</td>
875                        <td class="left">no</td>
876                        <td class="left">yes</td>
877                     </tr>
878                     <tr>
879                        <td class="left">Internet Explorer</td>
880                        <td class="left">no</td>
881                        <td class="left">no</td>
882                        <td class="left">yes</td>
883                        <td class="left">no</td>
884                     </tr>
885                     <tr>
886                        <td class="left">Konqueror</td>
887                        <td class="left">yes</td>
888                        <td class="left">no</td>
889                        <td class="left">no</td>
890                        <td class="left">no</td>
891                     </tr>
892                     <tr>
893                        <td class="left">Opera</td>
894                        <td class="left">yes (*)</td>
895                        <td class="left">no</td>
896                        <td class="left">no</td>
897                        <td class="left">no</td>
898                     </tr>
899                     <tr>
900                        <td class="left">Safari</td>
901                        <td class="left">no</td>
902                        <td class="left">no</td>
903                        <td class="left">no</td>
904                        <td class="left">yes</td>
905                     </tr>
906                  </tbody>
907               </table>
908               <p>(*) Does not implement the fallback behavior to "filename" described in <a href="#disposition.parameter.filename" title="Disposition Parameter: 'Filename'">Section&nbsp;3.3</a>.
909               </p>
910            </div>
911         </div>
912      </div>
913      <div id="change.log">
914         <h1 id="rfc.section.D"><a href="#rfc.section.D">D.</a>&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a></h1>
915         <div>
916            <h2 id="rfc.section.D.1"><a href="#rfc.section.D.1">D.1</a>&nbsp;Since draft-reschke-rfc2183-in-http-00
917            </h2>
918            <p id="rfc.section.D.1.p.1">Adjust terminology ("header" -&gt; "header field"). Update rfc2231-in-http reference.</p>
919         </div>
920         <div>
921            <h2 id="rfc.section.D.2"><a href="#rfc.section.D.2">D.2</a>&nbsp;Since draft-reschke-rfc2183-in-http-01
922            </h2>
923            <p id="rfc.section.D.2.p.1">Update rfc2231-in-http reference. Actually define the "filename" parameter. Add internationalization considerations. Add examples
924               using the RFC 5987 encoding. Add overview over other approaches, plus a table reporting implementation status. Add and resolve
925               issue "nodep2183". Add issues "asciivsiso", "deplboth", "quoted", and "registry".
926            </p>
927         </div>
928         <div>
929            <h2 id="rfc.section.D.3"><a href="#rfc.section.D.3">D.3</a>&nbsp;Since draft-reschke-rfc2183-in-http-02
930            </h2>
931            <p id="rfc.section.D.3.p.1">Add and close issue "docfallback". Close issues "asciivsiso", "deplboth", "quoted", and "registry".</p>
932         </div>
933         <div>
934            <h2 id="rfc.section.D.4"><a href="#rfc.section.D.4">D.4</a>&nbsp;Since draft-reschke-rfc2183-in-http-03
935            </h2>
936            <p id="rfc.section.D.4.p.1">Updated to be a Working Draft of the IETF HTTPbis Working Group.</p>
937         </div>
938         <div id="changes.since.00">
939            <h2 id="rfc.section.D.5"><a href="#rfc.section.D.5">D.5</a>&nbsp;<a href="#changes.since.00">Since draft-ietf-httpbis-content-disp-00</a></h2>
940            <p id="rfc.section.D.5.p.1">Closed issues: </p>
941            <ul>
942               <li>&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/242">http://tools.ietf.org/wg/httpbis/trac/ticket/242</a>&gt;: "handling of unknown disposition types"
943               </li>
944            </ul>
945            <p id="rfc.section.D.5.p.2">Slightly updated the notes about the proposed fallback behavior.</p>
946         </div>
947      </div>
948      <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1>
949      <p class="noprint"><a href="#rfc.index.C">C</a> <a href="#rfc.index.H">H</a> <a href="#rfc.index.I">I</a> <a href="#rfc.index.R">R</a>
950      </p>
951      <div class="print2col">
952         <ul class="ind">
953            <li><a id="rfc.index.C" href="#rfc.index.C"><b>C</b></a><ul>
954                  <li>Content-Disposition header&nbsp;&nbsp;<a href="#rfc.iref.c.1"><b>3</b></a>, <a href="#rfc.xref.header.field.definition.1">7.2</a></li>
955               </ul>
956            </li>
957            <li><a id="rfc.index.H" href="#rfc.index.H"><b>H</b></a><ul>
958                  <li>Headers&nbsp;&nbsp;
959                     <ul>
960                        <li>Content-Disposition&nbsp;&nbsp;<a href="#rfc.iref.h.1"><b>3</b></a>, <a href="#rfc.xref.header.field.definition.1">7.2</a></li>
961                     </ul>
962                  </li>
963               </ul>
964            </li>
965            <li><a id="rfc.index.I" href="#rfc.index.I"><b>I</b></a><ul>
966                  <li><em>ISO-8859-1</em>&nbsp;&nbsp;<a href="#rfc.xref.ISO-8859-1.1">3.3</a>, <a href="#ISO-8859-1"><b>9.1</b></a>, <a href="#rfc.xref.ISO-8859-1.2">C</a></li>
967               </ul>
968            </li>
969            <li><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul>
970                  <li><em>RFC2046</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2046.1">3.3</a>, <a href="#RFC2046"><b>9.2</b></a></li>
971                  <li><em>RFC2047</em>&nbsp;&nbsp;<a href="#RFC2047"><b>9.2</b></a>, <a href="#rfc.xref.RFC2047.1">C.1</a><ul>
972                        <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2047.1">C.1</a></li>
973                     </ul>
974                  </li>
975                  <li><em>RFC2119</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2119.1">2</a>, <a href="#RFC2119"><b>9.1</b></a></li>
976                  <li><em>RFC2183</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2183.1">1</a>, <a href="#rfc.xref.RFC2183.2">3.2</a>, <a href="#rfc.xref.RFC2183.3">3.4</a>, <a href="#rfc.xref.RFC2183.4">3.5</a>, <a href="#rfc.xref.RFC2183.5">7.1</a>, <a href="#RFC2183"><b>9.2</b></a>, <a href="#rfc.xref.RFC2183.6">A</a>, <a href="#rfc.xref.RFC2183.7">B</a><ul>
977                        <li><em>Section 2</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2183.7">B</a></li>
978                        <li><em>Section 2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2183.6">A</a></li>
979                        <li><em>Section 2.8</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2183.2">3.2</a>, <a href="#rfc.xref.RFC2183.3">3.4</a></li>
980                        <li><em>Section 9</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2183.4">3.5</a>, <a href="#rfc.xref.RFC2183.5">7.1</a></li>
981                     </ul>
982                  </li>
983                  <li><em>RFC2231</em>&nbsp;&nbsp;<a href="#RFC2231"><b>9.2</b></a>, <a href="#rfc.xref.RFC2231.1">C</a></li>
984                  <li><em>RFC2616</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.1">1</a>, <a href="#rfc.xref.RFC2616.2">1</a>, <a href="#rfc.xref.RFC2616.3">2</a>, <a href="#rfc.xref.RFC2616.4">3.1</a>, <a href="#rfc.xref.RFC2616.5">3.1</a>, <a href="#rfc.xref.RFC2616.6">3.1</a>, <a href="#rfc.xref.RFC2616.7">6</a>, <a href="#RFC2616"><b>9.1</b></a>, <a href="#rfc.xref.RFC2616.8">A</a>, <a href="#rfc.xref.RFC2616.9">C</a><ul>
985                        <li><em>Section 2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.3">2</a></li>
986                        <li><em>Section 2.2</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.5">3.1</a>, <a href="#rfc.xref.RFC2616.9">C</a></li>
987                        <li><em>Section 3.6</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.6">3.1</a></li>
988                        <li><em>Section 15.5</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.2">1</a></li>
989                        <li><em>Section 15</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.7">6</a></li>
990                        <li><em>Section 19.5.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.1">1</a>, <a href="#rfc.xref.RFC2616.8">A</a></li>
991                     </ul>
992                  </li>
993                  <li><em>RFC3629</em>&nbsp;&nbsp;<a href="#RFC3629"><b>9.2</b></a>, <a href="#rfc.xref.RFC3629.1">C.2</a></li>
994                  <li><em>RFC3864</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3864.1">7.2</a>, <a href="#RFC3864"><b>9.2</b></a></li>
995                  <li><em>RFC3986</em>&nbsp;&nbsp;<a href="#RFC3986"><b>9.2</b></a>, <a href="#rfc.xref.RFC3986.1">C.2</a><ul>
996                        <li><em>Section 2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">C.2</a></li>
997                     </ul>
998                  </li>
999                  <li><em>RFC5987</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5987.1">3.1</a>, <a href="#rfc.xref.RFC5987.2">3.1</a>, <a href="#rfc.xref.RFC5987.3">3.3</a>, <a href="#rfc.xref.RFC5987.4">4</a>, <a href="#rfc.xref.RFC5987.5">4</a>, <a href="#rfc.xref.RFC5987.6">5</a>, <a href="#rfc.xref.RFC5987.7">6</a>, <a href="#rfc.xref.RFC5987.8">6</a>, <a href="#RFC5987"><b>9.1</b></a>, <a href="#rfc.xref.RFC5987.9">A</a>, <a href="#rfc.xref.RFC5987.10">C</a><ul>
1000                        <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5987.2">3.1</a></li>
1001                        <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5987.8">6</a></li>
1002                     </ul>
1003                  </li>
1004               </ul>
1005            </li>
1006         </ul>
1007      </div>
1008      <div class="avoidbreak">
1009         <h1 id="rfc.authors"><a href="#rfc.authors">Author's Address</a></h1>
1010         <p><b>Julian F. Reschke</b><br>greenbytes GmbH<br>Hafenweg 16<br>Muenster, NW&nbsp;48155<br>Germany<br>Email: <a href="mailto:julian.reschke@greenbytes.de">julian.reschke@greenbytes.de</a><br>URI: <a href="http://greenbytes.de/tech/webdav/">http://greenbytes.de/tech/webdav/</a></p>
1011      </div>
1012   </body>
1013</html>
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