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Changeset 1417


Ignore:
Timestamp:
08/28/2011 07:56:24 AM (3 years ago)
Author:
julian.reschke@gmx.de
Message:

add considerations for new header fields (see #231)

Location:
draft-ietf-httpbis/latest
Files:
2 edited

Legend:

Unmodified
Added
Removed
  • draft-ietf-httpbis/latest/p2-semantics.html

    r1416 r1417  
    359359  }  
    360360  @bottom-center { 
    361        content: "Expires February 27, 2012";  
     361       content: "Expires February 29, 2012";  
    362362  }  
    363363  @bottom-right { 
     
    408408      <meta name="dct.creator" content="Reschke, J. F."> 
    409409      <meta name="dct.identifier" content="urn:ietf:id:draft-ietf-httpbis-p2-semantics-latest"> 
    410       <meta name="dct.issued" scheme="ISO8601" content="2011-08-26"> 
     410      <meta name="dct.issued" scheme="ISO8601" content="2011-08-28"> 
    411411      <meta name="dct.replaces" content="urn:ietf:rfc:2616"> 
    412412      <meta name="dct.abstract" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypertext information systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the seven-part specification that defines the protocol referred to as &#34;HTTP/1.1&#34; and, taken together, obsoletes RFC 2616. Part 2 defines the semantics of HTTP messages as expressed by request methods, request header fields, response status codes, and response header fields."> 
     
    439439            </tr> 
    440440            <tr> 
    441                <td class="left">Expires: February 27, 2012</td> 
     441               <td class="left">Expires: February 29, 2012</td> 
    442442               <td class="right">HP</td> 
    443443            </tr> 
     
    492492            <tr> 
    493493               <td class="left"></td> 
    494                <td class="right">August 26, 2011</td> 
     494               <td class="right">August 28, 2011</td> 
    495495            </tr> 
    496496         </tbody> 
     
    522522         in progress”. 
    523523      </p> 
    524       <p>This Internet-Draft will expire on February 27, 2012.</p> 
     524      <p>This Internet-Draft will expire on February 29, 2012.</p> 
    525525      <h1><a id="rfc.copyrightnotice" href="#rfc.copyrightnotice">Copyright Notice</a></h1> 
    526526      <p>Copyright © 2011 IETF Trust and the persons identified as the document authors. All rights reserved.</p> 
     
    558558         </li> 
    559559         <li>3.&nbsp;&nbsp;&nbsp;<a href="#header.fields">Header Fields</a><ul> 
    560                <li>3.1&nbsp;&nbsp;&nbsp;<a href="#request.header.fields">Request Header Fields</a></li> 
    561                <li>3.2&nbsp;&nbsp;&nbsp;<a href="#response.header.fields">Response Header Fields</a></li> 
     560               <li>3.1&nbsp;&nbsp;&nbsp;<a href="#considerations.for.creating.header.fields">Considerations for Creating Header Fields</a></li> 
     561               <li>3.2&nbsp;&nbsp;&nbsp;<a href="#request.header.fields">Request Header Fields</a></li> 
     562               <li>3.3&nbsp;&nbsp;&nbsp;<a href="#response.header.fields">Response Header Fields</a></li> 
    562563            </ul> 
    563564         </li> 
     
    842843      </p> 
    843844      <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a id="header.fields" href="#header.fields">Header Fields</a></h1> 
    844       <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;<a id="request.header.fields" href="#request.header.fields">Request Header Fields</a></h2> 
    845       <p id="rfc.section.3.1.p.1">The request header fields allow the client to pass additional information about the request, and about the client itself, 
     845      <p id="rfc.section.3.p.1">Header fields are key value pairs that can be used to communicate data about the message, its payload, the target resource, 
     846         or about the connection itself (i.e., control data). See <a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.17"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for a general definition of their syntax. 
     847      </p> 
     848      <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;<a id="considerations.for.creating.header.fields" href="#considerations.for.creating.header.fields">Considerations for Creating Header Fields</a></h2> 
     849      <p id="rfc.section.3.1.p.1">New header fields are registered using the procedures described in <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>. 
     850      </p> 
     851      <p id="rfc.section.3.1.p.2">The requirements for header field names are defined in <a href="http://tools.ietf.org/html/rfc3864#section-4.1">Section 4.1</a> of <a href="#RFC3864" id="rfc.xref.RFC3864.2"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>. Authors of specifications defining new fields are advised to keep the name as short as practical, and not to prefix them 
     852         with "X-" if they are to be registered (either immediately or in the future). 
     853      </p> 
     854      <p id="rfc.section.3.1.p.3">New header field values typically have their syntax defined using ABNF (<a href="#RFC5234" id="rfc.xref.RFC5234.3"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>), using the extensions defined in <a href="p1-messaging.html#notation.abnf" title="ABNF Extension: #rule">Section 1.2.1</a> of <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> as necessary, and are usually constrained to the range of ASCII characters. Header fields needing a greater range of characters 
     855         can use an encoding such as the one 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>. 
     856      </p> 
     857      <p id="rfc.section.3.1.p.4">Because commas (",") are used as a generic delimiter between field-values, they need to be treated with care if they are allowed 
     858         in the field-value's payload. Typically, components that might contain a comma are protected with double-quotes using the 
     859         quoted-string ABNF production (<a href="p1-messaging.html#field.rules" title="Common Field ABNF Rules">Section 3.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.19"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). 
     860      </p> 
     861      <p id="rfc.section.3.1.p.5">For example, a textual date and a URI (either of which might contain a comma) could be safely carried in field-values like 
     862         these: 
     863      </p> 
     864      <div id="rfc.figure.u.4"></div><pre class="text">  Example-URI-Field: "http://example.com/a.html,foo", 
     865                     "http://without-a-comma.example.com/" 
     866  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005" 
     867</pre><p id="rfc.section.3.1.p.7">Authors of specifications defining new header fields are advised to consider documenting: </p> 
     868      <ul> 
     869         <li>Whether the field is a single value, or whether it can be a list (delimited by commas; see <a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.20"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). 
     870         </li> 
     871         <li>Under what conditions the header field can be used; e.g., only i responses or requests, in all messages, only on responses 
     872            to a particular request method. 
     873         </li> 
     874         <li>Whether it is appropriate to list the field-name in the Connection header (i.e., if the header is to be hop-by-hop, see <a href="p1-messaging.html#header.connection" title="Connection">Section 9.1</a> of <a href="#Part1" id="rfc.xref.Part1.21"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). 
     875         </li> 
     876         <li>Under what conditions intermediaries are allowed to modify the header field's value, insert or delete it.</li> 
     877         <li>How the header might interact with caching (see <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
     878         </li> 
     879         <li>Whether the header field is useful or allowable in trailers (see <a href="p1-messaging.html#chunked.encoding" title="Chunked Transfer Coding">Section 6.2.1</a> of <a href="#Part1" id="rfc.xref.Part1.22"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). 
     880         </li> 
     881         <li>Whether the header field should be preserved across redirects.</li> 
     882      </ul> 
     883      <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a id="request.header.fields" href="#request.header.fields">Request Header Fields</a></h2> 
     884      <p id="rfc.section.3.2.p.1">The request header fields allow the client to pass additional information about the request, and about the client itself, 
    846885         to the server. These fields act as request modifiers, with semantics equivalent to the parameters on a programming language 
    847886         method invocation. 
     
    886925               <tr> 
    887926                  <td class="left">Host</td> 
    888                   <td class="left"><a href="p1-messaging.html#header.host" title="Host">Section 9.4</a> of <a href="#Part1" id="rfc.xref.Part1.17"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a></td> 
     927                  <td class="left"><a href="p1-messaging.html#header.host" title="Host">Section 9.4</a> of <a href="#Part1" id="rfc.xref.Part1.23"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a></td> 
    889928               </tr> 
    890929               <tr> 
     
    926965               <tr> 
    927966                  <td class="left">TE</td> 
    928                   <td class="left"><a href="p1-messaging.html#header.te" title="TE">Section 9.5</a> of <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a></td> 
     967                  <td class="left"><a href="p1-messaging.html#header.te" title="TE">Section 9.5</a> of <a href="#Part1" id="rfc.xref.Part1.24"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a></td> 
    929968               </tr> 
    930969               <tr> 
     
    935974         </table> 
    936975      </div> 
    937       <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a id="response.header.fields" href="#response.header.fields">Response Header Fields</a></h2> 
    938       <p id="rfc.section.3.2.p.1">The response header fields allow the server to pass additional information about the response which cannot be placed in the 
    939          Status-Line. These header fields give information about the server and about further access to the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.19"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). 
     976      <h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a>&nbsp;<a id="response.header.fields" href="#response.header.fields">Response Header Fields</a></h2> 
     977      <p id="rfc.section.3.3.p.1">The response header fields allow the server to pass additional information about the response which cannot be placed in the 
     978         Status-Line. These header fields give information about the server and about further access to the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.25"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). 
    940979      </p> 
    941980      <div id="rfc.table.u.3"> 
     
    954993               <tr> 
    955994                  <td class="left">Age</td> 
    956                   <td class="left"><a href="p6-cache.html#header.age" title="Age">Section 3.1</a> of <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a></td> 
     995                  <td class="left"><a href="p6-cache.html#header.age" title="Age">Section 3.1</a> of <a href="#Part6" id="rfc.xref.Part6.3"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a></td> 
    957996               </tr> 
    958997               <tr> 
     
    9821021               <tr> 
    9831022                  <td class="left">Vary</td> 
    984                   <td class="left"><a href="p6-cache.html#header.vary" title="Vary">Section 3.5</a> of <a href="#Part6" id="rfc.xref.Part6.3"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a></td> 
     1023                  <td class="left"><a href="p6-cache.html#header.vary" title="Vary">Section 3.5</a> of <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a></td> 
    9851024               </tr> 
    9861025               <tr> 
     
    9961035         client does not need to examine or display the Reason-Phrase. 
    9971036      </p> 
    998       <div id="rfc.figure.u.4"></div><pre class="inline"><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span><span id="rfc.iref.g.4"></span>  <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a>    = 3<a href="#notation" class="smpl">DIGIT</a> 
     1037      <div id="rfc.figure.u.5"></div><pre class="inline"><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span><span id="rfc.iref.g.4"></span>  <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a>    = 3<a href="#notation" class="smpl">DIGIT</a> 
    9991038  <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a>  = *( <a href="#notation" class="smpl">WSP</a> / <a href="#notation" class="smpl">VCHAR</a> / <a href="#core.rules" class="smpl">obs-text</a> ) 
    10001039</pre><p id="rfc.section.4.p.4">HTTP status codes are extensible. HTTP applications are not required to understand the meaning of all registered status codes, 
     
    12481287         a zero-length response body. They can require the presence of one or more particular HTTP response header(s). 
    12491288      </p> 
    1250       <p id="rfc.section.4.2.1.p.5">Likewise, their definitions can specify that caches are allowed to use heuristics to determine their freshness (see <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>; by default, it is not allowed), and can define how to determine the resource which they carry a representation for (see <a href="#identifying.response.associated.with.representation" title="Identifying the Resource Associated with a Representation">Section&nbsp;5.1</a>; by default, it is anonymous). 
     1289      <p id="rfc.section.4.2.1.p.5">Likewise, their definitions can specify that caches are allowed to use heuristics to determine their freshness (see <a href="#Part6" id="rfc.xref.Part6.5"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>; by default, it is not allowed), and can define how to determine the resource which they carry a representation for (see <a href="#identifying.response.associated.with.representation" title="Identifying the Resource Associated with a Representation">Section&nbsp;5.1</a>; by default, it is anonymous). 
    12511290      </p> 
    12521291      <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a id="representation" href="#representation">Representation</a></h1> 
     
    12551294         in an HTTP message, it is referred to as the payload of the message. HTTP representations are defined in <a href="#Part3" id="rfc.xref.Part3.5"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. 
    12561295      </p> 
    1257       <p id="rfc.section.5.p.2">A representation body is only present in a message when a message-body is present, as described in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.20"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. The representation body is obtained from the message-body by decoding any Transfer-Encoding that might have been applied 
     1296      <p id="rfc.section.5.p.2">A representation body is only present in a message when a message-body is present, as described in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.26"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. The representation body is obtained from the message-body by decoding any Transfer-Encoding that might have been applied 
    12581297         to ensure safe and proper transfer of the message. 
    12591298      </p> 
     
    12611300      <p id="rfc.section.5.1.p.1">It is sometimes necessary to determine an identifier for the resource associated with a representation.</p> 
    12621301      <p id="rfc.section.5.1.p.2">An HTTP request representation, when present, is always associated with an anonymous (i.e., unidentified) resource.</p> 
    1263       <p id="rfc.section.5.1.p.3">In the common case, an HTTP response is a representation of the target resource (see <a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.21"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). However, this is not always the case. To determine the URI of the resource a response is associated with, the following 
     1302      <p id="rfc.section.5.1.p.3">In the common case, an HTTP response is a representation of the target resource (see <a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.27"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). However, this is not always the case. To determine the URI of the resource a response is associated with, the following 
    12641303         rules are used (with the first applicable one being selected): 
    12651304      </p> 
     
    13531392         to reject the request. 
    13541393      </p> 
    1355       <p id="rfc.section.6.3.p.6">The response to a GET request is cacheable and <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests (see <a href="#Part6" id="rfc.xref.Part6.5"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
     1394      <p id="rfc.section.6.3.p.6">The response to a GET request is cacheable and <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests (see <a href="#Part6" id="rfc.xref.Part6.6"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
    13561395      </p> 
    13571396      <p id="rfc.section.6.3.p.7">See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;10.2</a> for security considerations when used for forms. 
     
    13641403         hypertext links for validity, accessibility, and recent modification. 
    13651404      </p> 
    1366       <p id="rfc.section.6.4.p.2">The response to a HEAD request is cacheable and <em class="bcp14">MAY</em> be used to satisfy a subsequent HEAD request; see <a href="#Part6" id="rfc.xref.Part6.6"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>. It also <em class="bcp14">MAY</em> be used to update a previously cached representation from that resource; if the new field values indicate that the cached 
     1405      <p id="rfc.section.6.4.p.2">The response to a HEAD request is cacheable and <em class="bcp14">MAY</em> be used to satisfy a subsequent HEAD request; see <a href="#Part6" id="rfc.xref.Part6.7"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>. It also <em class="bcp14">MAY</em> be used to update a previously cached representation from that resource; if the new field values indicate that the cached 
    13671406         representation differs from the current representation (as would be indicated by a change in Content-Length, ETag or Last-Modified), 
    13681407         then the cache <em class="bcp14">MUST</em> treat the cache entry as stale. 
     
    13931432         a Location header field (see <a href="#header.location" id="rfc.xref.header.location.2" title="Location">Section&nbsp;8.4</a>). 
    13941433      </p> 
    1395       <p id="rfc.section.6.5.p.5">Responses to POST requests are only cacheable when they include explicit freshness information (see <a href="p6-cache.html#calculating.freshness.lifetime" title="Calculating Freshness Lifetime">Section 2.3.1</a> of <a href="#Part6" id="rfc.xref.Part6.7"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). A cached POST response with a Content-Location header field (see <a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</a> of <a href="#Part3" id="rfc.xref.Part3.6"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) whose value is the effective Request URI <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests. 
     1434      <p id="rfc.section.6.5.p.5">Responses to POST requests are only cacheable when they include explicit freshness information (see <a href="p6-cache.html#calculating.freshness.lifetime" title="Calculating Freshness Lifetime">Section 2.3.1</a> of <a href="#Part6" id="rfc.xref.Part6.8"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). A cached POST response with a Content-Location header field (see <a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</a> of <a href="#Part3" id="rfc.xref.Part3.6"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) whose value is the effective Request URI <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests. 
    13961435      </p> 
    13971436      <p id="rfc.section.6.5.p.6">Note that POST caching is not widely implemented. However, the 303 (See Other) response can be used to direct the user agent 
     
    14581497      </p> 
    14591498      <p id="rfc.section.6.6.p.11">Responses to the PUT method are not cacheable. If a PUT request passes through a cache that has one or more stored responses 
    1460          for the effective request URI, those stored responses will be invalidated (see <a href="p6-cache.html#invalidation.after.updates.or.deletions" title="Request Methods that Invalidate">Section 2.5</a> of <a href="#Part6" id="rfc.xref.Part6.8"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
     1499         for the effective request URI, those stored responses will be invalidated (see <a href="p6-cache.html#invalidation.after.updates.or.deletions" title="Request Methods that Invalidate">Section 2.5</a> of <a href="#Part6" id="rfc.xref.Part6.9"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
    14611500      </p> 
    14621501      <div id="rfc.iref.d.1"></div> 
     
    14751514      </p> 
    14761515      <p id="rfc.section.6.7.p.4">Responses to the DELETE method are not cacheable. If a DELETE request passes through a cache that has one or more stored responses 
    1477          for the effective request URI, those stored responses will be invalidated (see <a href="p6-cache.html#invalidation.after.updates.or.deletions" title="Request Methods that Invalidate">Section 2.5</a> of <a href="#Part6" id="rfc.xref.Part6.9"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
     1516         for the effective request URI, those stored responses will be invalidated (see <a href="p6-cache.html#invalidation.after.updates.or.deletions" title="Request Methods that Invalidate">Section 2.5</a> of <a href="#Part6" id="rfc.xref.Part6.10"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
    14781517      </p> 
    14791518      <h2 id="rfc.section.6.8"><a href="#rfc.section.6.8">6.8</a>&nbsp;<a id="TRACE" href="#TRACE">TRACE</a></h2> 
     
    14841523      </p> 
    14851524      <p id="rfc.section.6.8.p.2">TRACE allows the client to see what is being received at the other end of the request chain and use that data for testing 
    1486          or diagnostic information. The value of the Via header field (<a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.22"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) is of particular interest, since it acts as a trace of the request chain. Use of the Max-Forwards header field allows the 
     1525         or diagnostic information. The value of the Via header field (<a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.28"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) is of particular interest, since it acts as a trace of the request chain. Use of the Max-Forwards header field allows the 
    14871526         client to limit the length of the request chain, which is useful for testing a chain of proxies forwarding messages in an 
    14881527         infinite loop. 
    14891528      </p> 
    1490       <p id="rfc.section.6.8.p.3">If the request is valid, the response <em class="bcp14">SHOULD</em> have a Content-Type of "message/http" (see <a href="p1-messaging.html#internet.media.type.message.http" title="Internet Media Type message/http">Section 10.3.1</a> of <a href="#Part1" id="rfc.xref.Part1.23"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and contain a message-body that encloses a copy of the entire request message. Responses to the TRACE method are not cacheable. 
     1529      <p id="rfc.section.6.8.p.3">If the request is valid, the response <em class="bcp14">SHOULD</em> have a Content-Type of "message/http" (see <a href="p1-messaging.html#internet.media.type.message.http" title="Internet Media Type message/http">Section 10.3.1</a> of <a href="#Part1" id="rfc.xref.Part1.29"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and contain a message-body that encloses a copy of the entire request message. Responses to the TRACE method are not cacheable. 
    14911530      </p> 
    14921531      <div id="rfc.iref.c.1"></div> 
     
    14961535         forwarding of packets until the connection is closed. 
    14971536      </p> 
    1498       <p id="rfc.section.6.9.p.2">When using CONNECT, the request-target <em class="bcp14">MUST</em> use the authority form (<a href="p1-messaging.html#request-target" title="request-target">Section 4.1.2</a> of <a href="#Part1" id="rfc.xref.Part1.24"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>); i.e., the request-target consists of only the host name and port number of the tunnel destination, separated by a colon. 
     1537      <p id="rfc.section.6.9.p.2">When using CONNECT, the request-target <em class="bcp14">MUST</em> use the authority form (<a href="p1-messaging.html#request-target" title="request-target">Section 4.1.2</a> of <a href="#Part1" id="rfc.xref.Part1.30"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>); i.e., the request-target consists of only the host name and port number of the tunnel destination, separated by a colon. 
    14991538         For example, 
    15001539      </p> 
    1501       <div id="rfc.figure.u.5"></div><pre class="text2">CONNECT server.example.com:80 HTTP/1.1 
     1540      <div id="rfc.figure.u.6"></div><pre class="text2">CONNECT server.example.com:80 HTTP/1.1 
    15021541Host: server.example.com:80 
    15031542 
     
    15061545      </p> 
    15071546      <p id="rfc.section.6.9.p.5">For example, proxy authentication might be used to establish the authority to create a tunnel:</p> 
    1508       <div id="rfc.figure.u.6"></div><pre class="text2">CONNECT server.example.com:80 HTTP/1.1 
     1547      <div id="rfc.figure.u.7"></div><pre class="text2">CONNECT server.example.com:80 HTTP/1.1 
    15091548Host: server.example.com:80 
    15101549Proxy-Authorization: basic aGVsbG86d29ybGQ= 
     
    15501589      <p id="rfc.section.7.1.1.p.1">The client <em class="bcp14">SHOULD</em> continue with its request. This interim response is used to inform the client that the initial part of the request has been 
    15511590         received and has not yet been rejected by the server. The client <em class="bcp14">SHOULD</em> continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The 
    1552          server <em class="bcp14">MUST</em> send a final response after the request has been completed. See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 7.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.25"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for detailed discussion of the use and handling of this status code. 
     1591         server <em class="bcp14">MUST</em> send a final response after the request has been completed. See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 7.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.31"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for detailed discussion of the use and handling of this status code. 
    15531592      </p> 
    15541593      <div id="rfc.iref.23"></div> 
    15551594      <div id="rfc.iref.s.3"></div> 
    15561595      <h3 id="rfc.section.7.1.2"><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;<a id="status.101" href="#status.101">101 Switching Protocols</a></h3> 
    1557       <p id="rfc.section.7.1.2.p.1">The server understands and is willing to comply with the client's request, via the Upgrade message header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 9.8</a> of <a href="#Part1" id="rfc.xref.Part1.26"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>), for a change in the application protocol being used on this connection. The server will switch protocols to those defined 
     1596      <p id="rfc.section.7.1.2.p.1">The server understands and is willing to comply with the client's request, via the Upgrade message header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 9.8</a> of <a href="#Part1" id="rfc.xref.Part1.32"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>), for a change in the application protocol being used on this connection. The server will switch protocols to those defined 
    15581597         by the response's Upgrade header field immediately after the empty line which terminates the 101 response. 
    15591598      </p> 
     
    15781617         <dd>a representation containing the request message as received by the end server.</dd> 
    15791618      </dl> 
    1580       <p id="rfc.section.7.2.1.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.10"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 200 responses. 
     1619      <p id="rfc.section.7.2.1.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.11"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 200 responses. 
    15811620      </p> 
    15821621      <div id="rfc.iref.25"></div> 
     
    16071646      <div id="rfc.iref.s.7"></div> 
    16081647      <h3 id="rfc.section.7.2.4"><a href="#rfc.section.7.2.4">7.2.4</a>&nbsp;<a id="status.203" href="#status.203">203 Non-Authoritative Information</a></h3> 
    1609       <p id="rfc.section.7.2.4.p.1">The representation in the response has been transformed or otherwise modified by a transforming proxy (<a href="p1-messaging.html#intermediaries" title="Intermediaries">Section 2.4</a> of <a href="#Part1" id="rfc.xref.Part1.27"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). Note that the behaviour of transforming intermediaries is controlled by the no-transform Cache-Control directive (<a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 3.2</a> of <a href="#Part6" id="rfc.xref.Part6.11"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
     1648      <p id="rfc.section.7.2.4.p.1">The representation in the response has been transformed or otherwise modified by a transforming proxy (<a href="p1-messaging.html#intermediaries" title="Intermediaries">Section 2.4</a> of <a href="#Part1" id="rfc.xref.Part1.33"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). Note that the behaviour of transforming intermediaries is controlled by the no-transform Cache-Control directive (<a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 3.2</a> of <a href="#Part6" id="rfc.xref.Part6.12"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). 
    16101649      </p> 
    16111650      <p id="rfc.section.7.2.4.p.2">This status code is only appropriate when the response status code would have been 200 (OK) otherwise. When the status code 
    1612          before transformation would have been different, the 214 Transformation Applied warn-code (<a href="p6-cache.html#header.warning" title="Warning">Section 3.6</a> of <a href="#Part6" id="rfc.xref.Part6.12"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) is appropriate. 
    1613       </p> 
    1614       <p id="rfc.section.7.2.4.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.13"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 203 responses. 
     1651         before transformation would have been different, the 214 Transformation Applied warn-code (<a href="p6-cache.html#header.warning" title="Warning">Section 3.6</a> of <a href="#Part6" id="rfc.xref.Part6.13"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) is appropriate. 
     1652      </p> 
     1653      <p id="rfc.section.7.2.4.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.14"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 203 responses. 
    16151654      </p> 
    16161655      <div id="rfc.iref.28"></div> 
     
    16421681         another input action. 
    16431682      </p> 
    1644       <p id="rfc.section.7.2.6.p.2">The message-body included with the response <em class="bcp14">MUST</em> be empty. Note that receivers still need to parse the response according to the algorithm defined in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.28"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. 
     1683      <p id="rfc.section.7.2.6.p.2">The message-body included with the response <em class="bcp14">MUST</em> be empty. Note that receivers still need to parse the response according to the algorithm defined in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.34"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. 
    16451684      </p> 
    16461685      <div id="rfc.iref.30"></div> 
     
    16501689         defined in <a href="p5-range.html#status.206" title="206 Partial Content">Section 3.1</a> of <a href="#Part5" id="rfc.xref.Part5.8"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>. 
    16511690      </p> 
    1652       <p id="rfc.section.7.2.7.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.14"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 206 responses. 
     1691      <p id="rfc.section.7.2.7.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.15"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 206 responses. 
    16531692      </p> 
    16541693      <h2 id="rfc.section.7.3"><a href="#rfc.section.7.3">7.3</a>&nbsp;<a id="status.3xx" href="#status.3xx">Redirection 3xx</a></h2> 
     
    16741713      <p id="rfc.section.7.3.1.p.3">If the server has a preferred choice of representation, it <em class="bcp14">SHOULD</em> include the specific URI for that representation in the Location field; user agents <em class="bcp14">MAY</em> use the Location field value for automatic redirection. 
    16751714      </p> 
    1676       <p id="rfc.section.7.3.1.p.4">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.15"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 300 responses. 
     1715      <p id="rfc.section.7.3.1.p.4">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.16"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 300 responses. 
    16771716      </p> 
    16781717      <div id="rfc.iref.32"></div> 
     
    16821721         request URI to one or more of the new references returned by the server, where possible. 
    16831722      </p> 
    1684       <p id="rfc.section.7.3.2.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.16"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 301 responses. 
     1723      <p id="rfc.section.7.3.2.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.17"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 301 responses. 
    16851724      </p> 
    16861725      <p id="rfc.section.7.3.2.p.3">The new permanent URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. Unless the request method was HEAD, the representation of the response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the new URI(s). 
     
    18551894         — that is left to the discretion of the server owner. 
    18561895      </p> 
    1857       <p id="rfc.section.7.4.11.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.17"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 410 responses. 
     1896      <p id="rfc.section.7.4.11.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.18"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 410 responses. 
    18581897      </p> 
    18591898      <div id="rfc.iref.50"></div> 
     
    19061945      <div id="rfc.iref.s.37"></div> 
    19071946      <h3 id="rfc.section.7.4.19"><a href="#rfc.section.7.4.19">7.4.19</a>&nbsp;<a id="status.426" href="#status.426">426 Upgrade Required</a></h3> 
    1908       <p id="rfc.section.7.4.19.p.1">The request can not be completed without a prior protocol upgrade. This response <em class="bcp14">MUST</em> include an Upgrade header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 9.8</a> of <a href="#Part1" id="rfc.xref.Part1.29"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) specifying the required protocols. 
    1909       </p> 
    1910       <div id="rfc.figure.u.7"></div>  
     1947      <p id="rfc.section.7.4.19.p.1">The request can not be completed without a prior protocol upgrade. This response <em class="bcp14">MUST</em> include an Upgrade header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 9.8</a> of <a href="#Part1" id="rfc.xref.Part1.35"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) specifying the required protocols. 
     1948      </p> 
     1949      <div id="rfc.figure.u.8"></div>  
    19111950      <p>Example:</p>  <pre class="text2">HTTP/1.1 426 Upgrade Required 
    19121951Upgrade: HTTP/2.0 
     
    19662005      <p id="rfc.section.7.5.6.p.1">The server does not support, or refuses to support, the protocol version that was used in the request message. The server 
    19672006         is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described 
    1968          in <a href="p1-messaging.html#http.version" title="Protocol Versioning">Section 2.6</a> of <a href="#Part1" id="rfc.xref.Part1.30"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, other than with this error message. The response <em class="bcp14">SHOULD</em> contain a representation describing why that version is not supported and what other protocols are supported by that server. 
     2007         in <a href="p1-messaging.html#http.version" title="Protocol Versioning">Section 2.6</a> of <a href="#Part1" id="rfc.xref.Part1.36"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, other than with this error message. The response <em class="bcp14">SHOULD</em> contain a representation describing why that version is not supported and what other protocols are supported by that server. 
    19692008      </p> 
    19702009      <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a>&nbsp;<a id="header.field.definitions" href="#header.field.definitions">Header Field Definitions</a></h1> 
     
    19762015         is strictly to inform the recipient of valid request methods associated with the resource. 
    19772016      </p> 
    1978       <div id="rfc.figure.u.8"></div><pre class="inline"><span id="rfc.iref.g.6"></span>  <a href="#header.allow" class="smpl">Allow</a> = #<a href="#method" class="smpl">Method</a> 
     2017      <div id="rfc.figure.u.9"></div><pre class="inline"><span id="rfc.iref.g.6"></span>  <a href="#header.allow" class="smpl">Allow</a> = #<a href="#method" class="smpl">Method</a> 
    19792018</pre><p id="rfc.section.8.1.p.3">Example of use:</p> 
    1980       <div id="rfc.figure.u.9"></div><pre class="text">  Allow: GET, HEAD, PUT 
     2019      <div id="rfc.figure.u.10"></div><pre class="text">  Allow: GET, HEAD, PUT 
    19812020</pre><p id="rfc.section.8.1.p.5">The actual set of allowed methods is defined by the origin server at the time of each request.</p> 
    19822021      <p id="rfc.section.8.1.p.6">A proxy <em class="bcp14">MUST NOT</em> modify the Allow header field — it does not need to understand all the methods specified in order to handle them according 
     
    19872026      <h2 id="rfc.section.8.2"><a href="#rfc.section.8.2">8.2</a>&nbsp;<a id="header.expect" href="#header.expect">Expect</a></h2> 
    19882027      <p id="rfc.section.8.2.p.1">The "Expect" header field is used to indicate that particular server behaviors are required by the client.</p> 
    1989       <div id="rfc.figure.u.10"></div><pre class="inline"><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="#header.expect" class="smpl">Expect</a>       = 1#<a href="#header.expect" class="smpl">expectation</a> 
     2028      <div id="rfc.figure.u.11"></div><pre class="inline"><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="#header.expect" class="smpl">Expect</a>       = 1#<a href="#header.expect" class="smpl">expectation</a> 
    19902029   
    19912030  <a href="#header.expect" class="smpl">expectation</a>  = "100-continue" / <a href="#header.expect" class="smpl">expectation-extension</a> 
     
    20062045      </p> 
    20072046      <p id="rfc.section.8.2.p.7">Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header field.</p> 
    2008       <p id="rfc.section.8.2.p.8">See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 7.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.31"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for the use of the 100 (Continue) status code. 
     2047      <p id="rfc.section.8.2.p.8">See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 7.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.37"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for the use of the 100 (Continue) status code. 
    20092048      </p> 
    20102049      <div id="rfc.iref.f.1"></div> 
     
    20132052      <p id="rfc.section.8.3.p.1">The "From" header field, if given, <em class="bcp14">SHOULD</em> contain an Internet e-mail address for the human user who controls the requesting user agent. The address <em class="bcp14">SHOULD</em> be machine-usable, as defined by "mailbox" in <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.1"><cite title="Internet Message Format">[RFC5322]</cite></a>: 
    20142053      </p> 
    2015       <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.11"></span>  <a href="#header.from" class="smpl">From</a>    = <a href="#header.from" class="smpl">mailbox</a> 
     2054      <div id="rfc.figure.u.12"></div><pre class="inline"><span id="rfc.iref.g.11"></span>  <a href="#header.from" class="smpl">From</a>    = <a href="#header.from" class="smpl">mailbox</a> 
    20162055   
    20172056  <a href="#header.from" class="smpl">mailbox</a> = &lt;mailbox, defined in <a href="#RFC5322" id="rfc.xref.RFC5322.2"><cite title="Internet Message Format">[RFC5322]</cite></a>, <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a>&gt; 
    20182057</pre><p id="rfc.section.8.3.p.3">An example is:</p> 
    2019       <div id="rfc.figure.u.12"></div><pre class="text">  From: webmaster@example.org 
     2058      <div id="rfc.figure.u.13"></div><pre class="text">  From: webmaster@example.org 
    20202059</pre><p id="rfc.section.8.3.p.5">This header field <em class="bcp14">MAY</em> be used for logging purposes and as a means for identifying the source of invalid or unwanted requests. It <em class="bcp14">SHOULD NOT</em> be used as an insecure form of access protection. The interpretation of this field is that the request is being performed 
    20212060         on behalf of the person given, who accepts responsibility for the method performed. In particular, robot agents <em class="bcp14">SHOULD</em> include this header field so that the person responsible for running the robot can be contacted if problems occur on the receiving 
     
    20402079      <p id="rfc.section.8.4.p.3">The field value consists of a single URI-reference. When it has the form of a relative reference (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-4.2">Section 4.2</a>), the final value is computed by resolving it against the effective request URI (<a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-5">Section 5</a>). 
    20412080      </p> 
    2042       <div id="rfc.figure.u.13"></div><pre class="inline"><span id="rfc.iref.g.12"></span>  <a href="#header.location" class="smpl">Location</a> = <a href="#abnf.dependencies" class="smpl">URI-reference</a> 
    2043 </pre><div id="rfc.figure.u.14"></div>  
     2081      <div id="rfc.figure.u.14"></div><pre class="inline"><span id="rfc.iref.g.12"></span>  <a href="#header.location" class="smpl">Location</a> = <a href="#abnf.dependencies" class="smpl">URI-reference</a> 
     2082</pre><div id="rfc.figure.u.15"></div>  
    20442083      <p>Examples are:</p>  <pre class="text">  Location: http://www.example.org/pub/WWW/People.html#tim 
    2045 </pre><div id="rfc.figure.u.15"></div><pre class="text">  Location: /index.html 
     2084</pre><div id="rfc.figure.u.16"></div><pre class="text">  Location: /index.html 
    20462085</pre><p id="rfc.section.8.4.p.7">There are circumstances in which a fragment identifier in a Location URI would not be appropriate. For instance, when it appears 
    20472086         in a 201 Created response, where the Location header field specifies the URI for the entire created resource. 
     
    20642103         to trace a request which appears to be failing or looping in mid-chain. 
    20652104      </p> 
    2066       <div id="rfc.figure.u.16"></div><pre class="inline"><span id="rfc.iref.g.13"></span>  <a href="#header.max-forwards" class="smpl">Max-Forwards</a> = 1*<a href="#notation" class="smpl">DIGIT</a> 
     2105      <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.13"></span>  <a href="#header.max-forwards" class="smpl">Max-Forwards</a> = 1*<a href="#notation" class="smpl">DIGIT</a> 
    20672106</pre><p id="rfc.section.8.5.p.3">The Max-Forwards value is a decimal integer indicating the remaining number of times this request message can be forwarded.</p> 
    20682107      <p id="rfc.section.8.5.p.4">Each recipient of a TRACE or OPTIONS request containing a Max-Forwards header field <em class="bcp14">MUST</em> check and update its value prior to forwarding the request. If the received value is zero (0), the recipient <em class="bcp14">MUST NOT</em> forward the request; instead, it <em class="bcp14">MUST</em> respond as the final recipient. If the received Max-Forwards value is greater than zero, then the forwarded message <em class="bcp14">MUST</em> contain an updated Max-Forwards field with a value decremented by one (1). 
     
    20842123         non-HTTP URIs (e.g., FTP). 
    20852124      </p> 
    2086       <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.14"></span>  <a href="#header.referer" class="smpl">Referer</a> = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a> 
     2125      <div id="rfc.figure.u.18"></div><pre class="inline"><span id="rfc.iref.g.14"></span>  <a href="#header.referer" class="smpl">Referer</a> = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a> 
    20872126</pre><p id="rfc.section.8.6.p.5">Example:</p> 
    2088       <div id="rfc.figure.u.18"></div><pre class="text">  Referer: http://www.example.org/hypertext/Overview.html 
     2127      <div id="rfc.figure.u.19"></div><pre class="text">  Referer: http://www.example.org/hypertext/Overview.html 
    20892128</pre><p id="rfc.section.8.6.p.7">If the field value is a relative URI, it <em class="bcp14">SHOULD</em> be interpreted relative to the effective request URI. The URI <em class="bcp14">MUST NOT</em> include a fragment. See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;10.2</a> for security considerations. 
    20902129      </p> 
     
    20972136      </p> 
    20982137      <p id="rfc.section.8.7.p.2">The value of this field can be either an HTTP-date or an integer number of seconds (in decimal) after the time of the response.</p> 
    2099       <div id="rfc.figure.u.19"></div><pre class="inline"><span id="rfc.iref.g.15"></span>  <a href="#header.retry-after" class="smpl">Retry-After</a> = <a href="#abnf.dependencies" class="smpl">HTTP-date</a> / <a href="#rule.delta-seconds" class="smpl">delta-seconds</a> 
     2138      <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.15"></span>  <a href="#header.retry-after" class="smpl">Retry-After</a> = <a href="#abnf.dependencies" class="smpl">HTTP-date</a> / <a href="#rule.delta-seconds" class="smpl">delta-seconds</a> 
    21002139</pre><div id="rule.delta-seconds"> 
    21012140         <p id="rfc.section.8.7.p.4">  Time spans are non-negative decimal integers, representing time in seconds.</p> 
    21022141      </div> 
    2103       <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.16"></span>  <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>  = 1*<a href="#notation" class="smpl">DIGIT</a> 
     2142      <div id="rfc.figure.u.21"></div><pre class="inline"><span id="rfc.iref.g.16"></span>  <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>  = 1*<a href="#notation" class="smpl">DIGIT</a> 
    21042143</pre><p id="rfc.section.8.7.p.6">Two examples of its use are</p> 
    2105       <div id="rfc.figure.u.21"></div><pre class="text">  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT 
     2144      <div id="rfc.figure.u.22"></div><pre class="text">  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT 
    21062145  Retry-After: 120 
    21072146</pre><p id="rfc.section.8.7.p.8">In the latter example, the delay is 2 minutes.</p> 
     
    21102149      <h2 id="rfc.section.8.8"><a href="#rfc.section.8.8">8.8</a>&nbsp;<a id="header.server" href="#header.server">Server</a></h2> 
    21112150      <p id="rfc.section.8.8.p.1">The "Server" header field contains information about the software used by the origin server to handle the request.</p> 
    2112       <p id="rfc.section.8.8.p.2">The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 6.3</a> of <a href="#Part1" id="rfc.xref.Part1.32"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.33"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the server and any significant subproducts. The product tokens are listed in order of their significance for 
     2151      <p id="rfc.section.8.8.p.2">The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 6.3</a> of <a href="#Part1" id="rfc.xref.Part1.38"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.39"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the server and any significant subproducts. The product tokens are listed in order of their significance for 
    21132152         identifying the application. 
    21142153      </p> 
    2115       <div id="rfc.figure.u.22"></div><pre class="inline"><span id="rfc.iref.g.17"></span>  <a href="#header.server" class="smpl">Server</a> = <a href="#abnf.dependencies" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#abnf.dependencies" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) ) 
     2154      <div id="rfc.figure.u.23"></div><pre class="inline"><span id="rfc.iref.g.17"></span>  <a href="#header.server" class="smpl">Server</a> = <a href="#abnf.dependencies" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#abnf.dependencies" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) ) 
    21162155</pre><p id="rfc.section.8.8.p.4">Example:</p> 
    2117       <div id="rfc.figure.u.23"></div><pre class="text">  Server: CERN/3.0 libwww/2.17 
    2118 </pre><p id="rfc.section.8.8.p.6">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server header field. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.34"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). 
     2156      <div id="rfc.figure.u.24"></div><pre class="text">  Server: CERN/3.0 libwww/2.17 
     2157</pre><p id="rfc.section.8.8.p.6">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server header field. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.40"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). 
    21192158      </p> 
    21202159      <div class="note" id="rfc.section.8.8.p.7">  
     
    21322171         user agent limitations. 
    21332172      </p> 
    2134       <p id="rfc.section.8.9.p.3">The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 6.3</a> of <a href="#Part1" id="rfc.xref.Part1.35"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.36"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the agent and its significant subproducts. By convention, the product tokens are listed in order of their significance 
     2173      <p id="rfc.section.8.9.p.3">The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 6.3</a> of <a href="#Part1" id="rfc.xref.Part1.41"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.42"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the agent and its significant subproducts. By convention, the product tokens are listed in order of their significance 
    21352174         for identifying the application. 
    21362175      </p> 
     
    21432182         doing so makes the field value more difficult to parse. 
    21442183      </p> 
    2145       <div id="rfc.figure.u.24"></div><pre class="inline"><span id="rfc.iref.g.18"></span>  <a href="#header.user-agent" class="smpl">User-Agent</a> = <a href="#abnf.dependencies" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#abnf.dependencies" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) ) 
     2184      <div id="rfc.figure.u.25"></div><pre class="inline"><span id="rfc.iref.g.18"></span>  <a href="#header.user-agent" class="smpl">User-Agent</a> = <a href="#abnf.dependencies" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#abnf.dependencies" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) ) 
    21462185</pre><p id="rfc.section.8.9.p.7">Example:</p> 
    2147       <div id="rfc.figure.u.25"></div><pre class="text">  User-Agent: CERN-LineMode/2.15 libwww/2.17b3 
     2186      <div id="rfc.figure.u.26"></div><pre class="text">  User-Agent: CERN-LineMode/2.15 libwww/2.17b3 
    21482187</pre><h1 id="rfc.section.9"><a href="#rfc.section.9">9.</a>&nbsp;<a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1> 
    21492188      <h2 id="rfc.section.9.1"><a href="#rfc.section.9.1">9.1</a>&nbsp;<a id="method.registration" href="#method.registration">Method Registry</a></h2> 
     
    24562495      </div> 
    24572496      <h2 id="rfc.section.9.3"><a href="#rfc.section.9.3">9.3</a>&nbsp;<a id="header.field.registration" href="#header.field.registration">Header Field Registration</a></h2> 
    2458       <p id="rfc.section.9.3.p.1">The Message Header Field Registry located at &lt;<a href="http://www.iana.org/assignments/message-headers/message-header-index.html">http://www.iana.org/assignments/message-headers/message-header-index.html</a>&gt; shall be updated with the permanent registrations below (see <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>): 
     2497      <p id="rfc.section.9.3.p.1">The Message Header Field Registry located at &lt;<a href="http://www.iana.org/assignments/message-headers/message-header-index.html">http://www.iana.org/assignments/message-headers/message-header-index.html</a>&gt; shall be updated with the permanent registrations below (see <a href="#RFC3864" id="rfc.xref.RFC3864.3"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>): 
    24592498      </p> 
    24602499      <div id="rfc.table.3"> 
     
    25972636      </p> 
    25982637      <h1 id="rfc.section.11"><a href="#rfc.section.11">11.</a>&nbsp;<a id="acks" href="#acks">Acknowledgments</a></h1> 
    2599       <p id="rfc.section.11.p.1">See <a href="p1-messaging.html#acks" title="Acknowledgments">Section 12</a> of <a href="#Part1" id="rfc.xref.Part1.37"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. 
     2638      <p id="rfc.section.11.p.1">See <a href="p1-messaging.html#acks" title="Acknowledgments">Section 12</a> of <a href="#Part1" id="rfc.xref.Part1.43"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. 
    26002639      </p> 
    26012640      <h1 id="rfc.references"><a id="rfc.section.12" href="#rfc.section.12">12.</a> References 
     
    26522691      <h2 id="rfc.references.2"><a href="#rfc.section.12.2" id="rfc.section.12.2">12.2</a> Informative References 
    26532692      </h2> 
    2654       <table>                 
     2693      <table>                   
    26552694         <tr> 
    26562695            <td class="reference"><b id="RFC1945">[RFC1945]</b></td> 
     
    26932732            </td> 
    26942733         </tr> 
     2734         <tr> 
     2735            <td class="reference"><b id="RFC5987">[RFC5987]</b></td> 
     2736            <td class="top"><a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">Reschke, J.</a>, “<a href="http://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. 
     2737            </td> 
     2738         </tr> 
    26952739      </table> 
    26962740      <div class="avoidbreak"> 
     
    27462790      </p> 
    27472791      <p id="rfc.section.A.p.14">In the description of the Server header field, the Via field was described as a SHOULD. The requirement was and is stated 
    2748          correctly in the description of the Via header field in <a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.38"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. (<a href="#header.server" id="rfc.xref.header.server.4" title="Server">Section&nbsp;8.8</a>) 
     2792         correctly in the description of the Via header field in <a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.44"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. (<a href="#header.server" id="rfc.xref.header.server.4" title="Server">Section&nbsp;8.8</a>) 
    27492793      </p> 
    27502794      <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;<a id="collected.abnf" href="#collected.abnf">Collected ABNF</a></h1> 
    2751       <div id="rfc.figure.u.26"></div> <pre class="inline"><a href="#header.allow" class="smpl">Allow</a> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ] 
     2795      <div id="rfc.figure.u.27"></div> <pre class="inline"><a href="#header.allow" class="smpl">Allow</a> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ] 
    27522796 
    27532797<a href="#header.expect" class="smpl">Expect</a> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] ) 
     
    27962840 
    27972841<a href="#core.rules" class="smpl">token</a> = &lt;token, defined in [Part1], Section 3.2.3&gt; 
    2798 </pre> <div id="rfc.figure.u.27"></div> 
     2842</pre> <div id="rfc.figure.u.28"></div> 
    27992843      <p>ABNF diagnostics:</p><pre class="inline">; Allow defined but not used 
    28002844; Expect defined but not used 
     
    30763120      </ul> 
    30773121      <h2 id="rfc.section.C.18"><a href="#rfc.section.C.18">C.18</a>&nbsp;<a id="changes.since.16" href="#changes.since.16">Since draft-ietf-httpbis-p2-semantics-16</a></h2> 
    3078       <p id="rfc.section.C.18.p.1">None yet.</p> 
     3122      <p id="rfc.section.C.18.p.1">Work-in-progress: </p> 
     3123      <ul> 
     3124         <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/231">http://tools.ietf.org/wg/httpbis/trac/ticket/231</a>&gt;: "Considerations for new headers" 
     3125         </li> 
     3126      </ul> 
    30793127      <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1> 
    30803128      <p class="noprint"><a href="#rfc.index.1">1</a> <a href="#rfc.index.2">2</a> <a href="#rfc.index.3">3</a> <a href="#rfc.index.4">4</a> <a href="#rfc.index.5">5</a> <a href="#rfc.index.A">A</a> <a href="#rfc.index.C">C</a> <a href="#rfc.index.D">D</a> <a href="#rfc.index.E">E</a> <a href="#rfc.index.F">F</a> <a href="#rfc.index.G">G</a> <a href="#rfc.index.H">H</a> <a href="#rfc.index.I">I</a> <a href="#rfc.index.L">L</a> <a href="#rfc.index.M">M</a> <a href="#rfc.index.O">O</a> <a href="#rfc.index.P">P</a> <a href="#rfc.index.R">R</a> <a href="#rfc.index.S">S</a> <a href="#rfc.index.T">T</a> <a href="#rfc.index.U">U</a>  
     
    31403188            </li> 
    31413189            <li><a id="rfc.index.A" href="#rfc.index.A"><b>A</b></a><ul> 
    3142                   <li>Allow header field&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">2</a>, <a href="#rfc.xref.header.allow.2">3.2</a>, <a href="#rfc.iref.a.1"><b>8.1</b></a>, <a href="#rfc.xref.header.allow.3">9.3</a>, <a href="#rfc.xref.header.allow.4">A</a></li> 
     3190                  <li>Allow header field&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">2</a>, <a href="#rfc.xref.header.allow.2">3.3</a>, <a href="#rfc.iref.a.1"><b>8.1</b></a>, <a href="#rfc.xref.header.allow.3">9.3</a>, <a href="#rfc.xref.header.allow.4">A</a></li> 
    31433191               </ul> 
    31443192            </li> 
     
    31523200            </li> 
    31533201            <li><a id="rfc.index.E" href="#rfc.index.E"><b>E</b></a><ul> 
    3154                   <li>Expect header field&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">3.1</a>, <a href="#rfc.xref.header.expect.2">7.4.18</a>, <a href="#rfc.iref.e.1"><b>8.2</b></a>, <a href="#rfc.xref.header.expect.3">9.3</a></li> 
     3202                  <li>Expect header field&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">3.2</a>, <a href="#rfc.xref.header.expect.2">7.4.18</a>, <a href="#rfc.iref.e.1"><b>8.2</b></a>, <a href="#rfc.xref.header.expect.3">9.3</a></li> 
    31553203               </ul> 
    31563204            </li> 
    31573205            <li><a id="rfc.index.F" href="#rfc.index.F"><b>F</b></a><ul> 
    3158                   <li>From header field&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">3.1</a>, <a href="#rfc.iref.f.1"><b>8.3</b></a>, <a href="#rfc.xref.header.from.2">9.3</a></li> 
     3206                  <li>From header field&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">3.2</a>, <a href="#rfc.iref.f.1"><b>8.3</b></a>, <a href="#rfc.xref.header.from.2">9.3</a></li> 
    31593207               </ul> 
    31603208            </li> 
     
    31883236                  <li>Header Fields&nbsp;&nbsp; 
    31893237                     <ul> 
    3190                         <li>Allow&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">2</a>, <a href="#rfc.xref.header.allow.2">3.2</a>, <a href="#rfc.iref.h.2"><b>8.1</b></a>, <a href="#rfc.xref.header.allow.3">9.3</a>, <a href="#rfc.xref.header.allow.4">A</a></li> 
    3191                         <li>Expect&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">3.1</a>, <a href="#rfc.xref.header.expect.2">7.4.18</a>, <a href="#rfc.iref.h.3"><b>8.2</b></a>, <a href="#rfc.xref.header.expect.3">9.3</a></li> 
    3192                         <li>From&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">3.1</a>, <a href="#rfc.iref.h.4"><b>8.3</b></a>, <a href="#rfc.xref.header.from.2">9.3</a></li> 
    3193                         <li>Location&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">3.2</a>, <a href="#rfc.xref.header.location.2">6.5</a>, <a href="#rfc.iref.h.5"><b>8.4</b></a>, <a href="#rfc.xref.header.location.3">9.3</a>, <a href="#rfc.xref.header.location.4">A</a></li> 
    3194                         <li>Max-Forwards&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">3.1</a>, <a href="#rfc.xref.header.max-forwards.2">6.2</a>, <a href="#rfc.xref.header.max-forwards.3">6.8</a>, <a href="#rfc.iref.h.6"><b>8.5</b></a>, <a href="#rfc.xref.header.max-forwards.4">9.3</a>, <a href="#rfc.xref.header.max-forwards.5">A</a></li> 
    3195                         <li>Referer&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">3.1</a>, <a href="#rfc.iref.h.7"><b>8.6</b></a>, <a href="#rfc.xref.header.referer.2">9.3</a>, <a href="#rfc.xref.header.referer.3">A</a></li> 
    3196                         <li>Retry-After&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">3.2</a>, <a href="#rfc.xref.header.retry-after.2">7.5.4</a>, <a href="#rfc.iref.h.8"><b>8.7</b></a>, <a href="#rfc.xref.header.retry-after.3">9.3</a></li> 
    3197                         <li>Server&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">3.2</a>, <a href="#rfc.iref.h.9"><b>8.8</b></a>, <a href="#rfc.xref.header.server.2">9.3</a>, <a href="#rfc.xref.header.server.3">10.1</a>, <a href="#rfc.xref.header.server.4">A</a></li> 
    3198                         <li>User-Agent&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">3.1</a>, <a href="#rfc.iref.h.10"><b>8.9</b></a>, <a href="#rfc.xref.header.user-agent.2">9.3</a>, <a href="#rfc.xref.header.user-agent.3">10.1</a></li> 
     3238                        <li>Allow&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">2</a>, <a href="#rfc.xref.header.allow.2">3.3</a>, <a href="#rfc.iref.h.2"><b>8.1</b></a>, <a href="#rfc.xref.header.allow.3">9.3</a>, <a href="#rfc.xref.header.allow.4">A</a></li> 
     3239                        <li>Expect&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">3.2</a>, <a href="#rfc.xref.header.expect.2">7.4.18</a>, <a href="#rfc.iref.h.3"><b>8.2</b></a>, <a href="#rfc.xref.header.expect.3">9.3</a></li> 
     3240                        <li>From&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">3.2</a>, <a href="#rfc.iref.h.4"><b>8.3</b></a>, <a href="#rfc.xref.header.from.2">9.3</a></li> 
     3241                        <li>Location&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">3.3</a>, <a href="#rfc.xref.header.location.2">6.5</a>, <a href="#rfc.iref.h.5"><b>8.4</b></a>, <a href="#rfc.xref.header.location.3">9.3</a>, <a href="#rfc.xref.header.location.4">A</a></li> 
     3242                        <li>Max-Forwards&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">3.2</a>, <a href="#rfc.xref.header.max-forwards.2">6.2</a>, <a href="#rfc.xref.header.max-forwards.3">6.8</a>, <a href="#rfc.iref.h.6"><b>8.5</b></a>, <a href="#rfc.xref.header.max-forwards.4">9.3</a>, <a href="#rfc.xref.header.max-forwards.5">A</a></li> 
     3243                        <li>Referer&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">3.2</a>, <a href="#rfc.iref.h.7"><b>8.6</b></a>, <a href="#rfc.xref.header.referer.2">9.3</a>, <a href="#rfc.xref.header.referer.3">A</a></li> 
     3244                        <li>Retry-After&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">3.3</a>, <a href="#rfc.xref.header.retry-after.2">7.5.4</a>, <a href="#rfc.iref.h.8"><b>8.7</b></a>, <a href="#rfc.xref.header.retry-after.3">9.3</a></li> 
     3245                        <li>Server&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">3.3</a>, <a href="#rfc.iref.h.9"><b>8.8</b></a>, <a href="#rfc.xref.header.server.2">9.3</a>, <a href="#rfc.xref.header.server.3">10.1</a>, <a href="#rfc.xref.header.server.4">A</a></li> 
     3246                        <li>User-Agent&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">3.2</a>, <a href="#rfc.iref.h.10"><b>8.9</b></a>, <a href="#rfc.xref.header.user-agent.2">9.3</a>, <a href="#rfc.xref.header.user-agent.3">10.1</a></li> 
    31993247                     </ul> 
    32003248                  </li> 
     
    32063254            </li> 
    32073255            <li><a id="rfc.index.L" href="#rfc.index.L"><b>L</b></a><ul> 
    3208                   <li>Location header field&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">3.2</a>, <a href="#rfc.xref.header.location.2">6.5</a>, <a href="#rfc.iref.l.1"><b>8.4</b></a>, <a href="#rfc.xref.header.location.3">9.3</a>, <a href="#rfc.xref.header.location.4">A</a></li> 
     3256                  <li>Location header field&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">3.3</a>, <a href="#rfc.xref.header.location.2">6.5</a>, <a href="#rfc.iref.l.1"><b>8.4</b></a>, <a href="#rfc.xref.header.location.3">9.3</a>, <a href="#rfc.xref.header.location.4">A</a></li> 
    32093257               </ul> 
    32103258            </li> 
    32113259            <li><a id="rfc.index.M" href="#rfc.index.M"><b>M</b></a><ul> 
    3212                   <li>Max-Forwards header field&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">3.1</a>, <a href="#rfc.xref.header.max-forwards.2">6.2</a>, <a href="#rfc.xref.header.max-forwards.3">6.8</a>, <a href="#rfc.iref.m.9"><b>8.5</b></a>, <a href="#rfc.xref.header.max-forwards.4">9.3</a>, <a href="#rfc.xref.header.max-forwards.5">A</a></li> 
     3260                  <li>Max-Forwards header field&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">3.2</a>, <a href="#rfc.xref.header.max-forwards.2">6.2</a>, <a href="#rfc.xref.header.max-forwards.3">6.8</a>, <a href="#rfc.iref.m.9"><b>8.5</b></a>, <a href="#rfc.xref.header.max-forwards.4">9.3</a>, <a href="#rfc.xref.header.max-forwards.5">A</a></li> 
    32133261                  <li>Methods&nbsp;&nbsp; 
    32143262                     <ul> 
     
    32303278            </li> 
    32313279            <li><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul> 
    3232                   <li><em>Part1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1</a>, <a href="#rfc.xref.Part1.2">1.2</a>, <a href="#rfc.xref.Part1.3">1.2.1</a>, <a href="#rfc.xref.Part1.4">1.2.1</a>, <a href="#rfc.xref.Part1.5">1.2.1</a>, <a href="#rfc.xref.Part1.6">1.2.1</a>, <a href="#rfc.xref.Part1.7">1.2.1</a>, <a href="#rfc.xref.Part1.8">1.2.1</a>, <a href="#rfc.xref.Part1.9">1.2.2</a>, <a href="#rfc.xref.Part1.10">1.2.2</a>, <a href="#rfc.xref.Part1.11">1.2.2</a>, <a href="#rfc.xref.Part1.12">1.2.2</a>, <a href="#rfc.xref.Part1.13">1.2.2</a>, <a href="#rfc.xref.Part1.14">1.2.2</a>, <a href="#rfc.xref.Part1.15">2</a>, <a href="#rfc.xref.Part1.16">2.2.1</a>, <a href="#rfc.xref.Part1.17">3.1</a>, <a href="#rfc.xref.Part1.18">3.1</a>, <a href="#rfc.xref.Part1.19">3.2</a>, <a href="#rfc.xref.Part1.20">5</a>, <a href="#rfc.xref.Part1.21">5.1</a>, <a href="#rfc.xref.Part1.22">6.8</a>, <a href="#rfc.xref.Part1.23">6.8</a>, <a href="#rfc.xref.Part1.24">6.9</a>, <a href="#rfc.xref.Part1.25">7.1.1</a>, <a href="#rfc.xref.Part1.26">7.1.2</a>, <a href="#rfc.xref.Part1.27">7.2.4</a>, <a href="#rfc.xref.Part1.28">7.2.6</a>, <a href="#rfc.xref.Part1.29">7.4.19</a>, <a href="#rfc.xref.Part1.30">7.5.6</a>, <a href="#rfc.xref.Part1.31">8.2</a>, <a href="#rfc.xref.Part1.32">8.8</a>, <a href="#rfc.xref.Part1.33">8.8</a>, <a href="#rfc.xref.Part1.34">8.8</a>, <a href="#rfc.xref.Part1.35">8.9</a>, <a href="#rfc.xref.Part1.36">8.9</a>, <a href="#rfc.xref.Part1.37">11</a>, <a href="#Part1"><b>12.1</b></a>, <a href="#rfc.xref.Part1.38">A</a><ul> 
     3280                  <li><em>Part1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1</a>, <a href="#rfc.xref.Part1.2">1.2</a>, <a href="#rfc.xref.Part1.3">1.2.1</a>, <a href="#rfc.xref.Part1.4">1.2.1</a>, <a href="#rfc.xref.Part1.5">1.2.1</a>, <a href="#rfc.xref.Part1.6">1.2.1</a>, <a href="#rfc.xref.Part1.7">1.2.1</a>, <a href="#rfc.xref.Part1.8">1.2.1</a>, <a href="#rfc.xref.Part1.9">1.2.2</a>, <a href="#rfc.xref.Part1.10">1.2.2</a>, <a href="#rfc.xref.Part1.11">1.2.2</a>, <a href="#rfc.xref.Part1.12">1.2.2</a>, <a href="#rfc.xref.Part1.13">1.2.2</a>, <a href="#rfc.xref.Part1.14">1.2.2</a>, <a href="#rfc.xref.Part1.15">2</a>, <a href="#rfc.xref.Part1.16">2.2.1</a>, <a href="#rfc.xref.Part1.17">3</a>, <a href="#rfc.xref.Part1.18">3.1</a>, <a href="#rfc.xref.Part1.19">3.1</a>, <a href="#rfc.xref.Part1.20">3.1</a>, <a href="#rfc.xref.Part1.21">3.1</a>, <a href="#rfc.xref.Part1.22">3.1</a>, <a href="#rfc.xref.Part1.23">3.2</a>, <a href="#rfc.xref.Part1.24">3.2</a>, <a href="#rfc.xref.Part1.25">3.3</a>, <a href="#rfc.xref.Part1.26">5</a>, <a href="#rfc.xref.Part1.27">5.1</a>, <a href="#rfc.xref.Part1.28">6.8</a>, <a href="#rfc.xref.Part1.29">6.8</a>, <a href="#rfc.xref.Part1.30">6.9</a>, <a href="#rfc.xref.Part1.31">7.1.1</a>, <a href="#rfc.xref.Part1.32">7.1.2</a>, <a href="#rfc.xref.Part1.33">7.2.4</a>, <a href="#rfc.xref.Part1.34">7.2.6</a>, <a href="#rfc.xref.Part1.35">7.4.19</a>, <a href="#rfc.xref.Part1.36">7.5.6</a>, <a href="#rfc.xref.Part1.37">8.2</a>, <a href="#rfc.xref.Part1.38">8.8</a>, <a href="#rfc.xref.Part1.39">8.8</a>, <a href="#rfc.xref.Part1.40">8.8</a>, <a href="#rfc.xref.Part1.41">8.9</a>, <a href="#rfc.xref.Part1.42">8.9</a>, <a href="#rfc.xref.Part1.43">11</a>, <a href="#Part1"><b>12.1</b></a>, <a href="#rfc.xref.Part1.44">A</a><ul> 
    32333281                        <li><em>Section 1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.2">1.2</a></li> 
     3282                        <li><em>Section 1.2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.18">3.1</a></li> 
    32343283                        <li><em>Section 1.2.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.4">1.2.1</a>, <a href="#rfc.xref.Part1.5">1.2.1</a>, <a href="#rfc.xref.Part1.6">1.2.1</a></li> 
    3235                         <li><em>Section 2.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.27">7.2.4</a></li> 
    3236                         <li><em>Section 2.6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.30">7.5.6</a></li> 
     3284                        <li><em>Section 2.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.33">7.2.4</a></li> 
     3285                        <li><em>Section 2.6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.36">7.5.6</a></li> 
    32373286                        <li><em>Section 2.7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.9">1.2.2</a>, <a href="#rfc.xref.Part1.12">1.2.2</a>, <a href="#rfc.xref.Part1.14">1.2.2</a></li> 
    3238                         <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.10">1.2.2</a>, <a href="#rfc.xref.Part1.33">8.8</a>, <a href="#rfc.xref.Part1.36">8.9</a></li> 
    3239                         <li><em>Section 3.2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.7">1.2.1</a>, <a href="#rfc.xref.Part1.8">1.2.1</a></li> 
    3240                         <li><em>Section 3.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.16">2.2.1</a>, <a href="#rfc.xref.Part1.20">5</a>, <a href="#rfc.xref.Part1.28">7.2.6</a></li> 
    3241                         <li><em>Section 4.1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.24">6.9</a></li> 
    3242                         <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.15">2</a>, <a href="#rfc.xref.Part1.19">3.2</a>, <a href="#rfc.xref.Part1.21">5.1</a></li> 
     3287                        <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.10">1.2.2</a>, <a href="#rfc.xref.Part1.17">3</a>, <a href="#rfc.xref.Part1.20">3.1</a>, <a href="#rfc.xref.Part1.39">8.8</a>, <a href="#rfc.xref.Part1.42">8.9</a></li> 
     3288                        <li><em>Section 3.2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.7">1.2.1</a>, <a href="#rfc.xref.Part1.8">1.2.1</a>, <a href="#rfc.xref.Part1.19">3.1</a></li> 
     3289                        <li><em>Section 3.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.16">2.2.1</a>, <a href="#rfc.xref.Part1.26">5</a>, <a href="#rfc.xref.Part1.34">7.2.6</a></li> 
     3290                        <li><em>Section 4.1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.30">6.9</a></li> 
     3291                        <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.15">2</a>, <a href="#rfc.xref.Part1.25">3.3</a>, <a href="#rfc.xref.Part1.27">5.1</a></li> 
    32433292                        <li><em>Section 6.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.11">1.2.2</a></li> 
    3244                         <li><em>Section 6.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.13">1.2.2</a>, <a href="#rfc.xref.Part1.32">8.8</a>, <a href="#rfc.xref.Part1.35">8.9</a></li> 
    3245                         <li><em>Section 7.2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.25">7.1.1</a>, <a href="#rfc.xref.Part1.31">8.2</a></li> 
    3246                         <li><em>Section 9.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.17">3.1</a></li> 
    3247                         <li><em>Section 9.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.18">3.1</a></li> 
    3248                         <li><em>Section 9.8</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.26">7.1.2</a>, <a href="#rfc.xref.Part1.29">7.4.19</a></li> 
    3249                         <li><em>Section 9.9</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.22">6.8</a>, <a href="#rfc.xref.Part1.34">8.8</a>, <a href="#rfc.xref.Part1.38">A</a></li> 
    3250                         <li><em>Section 10.3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.23">6.8</a></li> 
    3251                         <li><em>Section 12</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.37">11</a></li> 
     3293                        <li><em>Section 6.2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.22">3.1</a></li> 
     3294                        <li><em>Section 6.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.13">1.2.2</a>, <a href="#rfc.xref.Part1.38">8.8</a>, <a href="#rfc.xref.Part1.41">8.9</a></li> 
     3295                        <li><em>Section 7.2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.31">7.1.1</a>, <a href="#rfc.xref.Part1.37">8.2</a></li> 
     3296                        <li><em>Section 9.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.21">3.1</a></li> 
     3297                        <li><em>Section 9.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.23">3.2</a></li> 
     3298                        <li><em>Section 9.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.24">3.2</a></li> 
     3299                        <li><em>Section 9.8</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.32">7.1.2</a>, <a href="#rfc.xref.Part1.35">7.4.19</a></li> 
     3300                        <li><em>Section 9.9</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.28">6.8</a>, <a href="#rfc.xref.Part1.40">8.8</a>, <a href="#rfc.xref.Part1.44">A</a></li> 
     3301                        <li><em>Section 10.3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.29">6.8</a></li> 
     3302                        <li><em>Section 12</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.43">11</a></li> 
    32523303                     </ul> 
    32533304                  </li> 
    3254                   <li><em>Part3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.1">3.1</a>, <a href="#rfc.xref.Part3.2">3.1</a>, <a href="#rfc.xref.Part3.3">3.1</a>, <a href="#rfc.xref.Part3.4">3.1</a>, <a href="#rfc.xref.Part3.5">5</a>, <a href="#rfc.xref.Part3.6">6.5</a>, <a href="#rfc.xref.Part3.7">7.3.1</a>, <a href="#rfc.xref.Part3.8">7.4.7</a>, <a href="#rfc.xref.Part3.9">8.4</a>, <a href="#Part3"><b>12.1</b></a><ul> 
     3305                  <li><em>Part3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.1">3.2</a>, <a href="#rfc.xref.Part3.2">3.2</a>, <a href="#rfc.xref.Part3.3">3.2</a>, <a href="#rfc.xref.Part3.4">3.2</a>, <a href="#rfc.xref.Part3.5">5</a>, <a href="#rfc.xref.Part3.6">6.5</a>, <a href="#rfc.xref.Part3.7">7.3.1</a>, <a href="#rfc.xref.Part3.8">7.4.7</a>, <a href="#rfc.xref.Part3.9">8.4</a>, <a href="#Part3"><b>12.1</b></a><ul> 
    32553306                        <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.7">7.3.1</a></li> 
    3256                         <li><em>Section 6.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.1">3.1</a></li> 
     3307                        <li><em>Section 6.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.1">3.2</a></li> 
    32573308                        <li><em>Section 6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.8">7.4.7</a></li> 
    3258                         <li><em>Section 6.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.2">3.1</a></li> 
    3259                         <li><em>Section 6.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.3">3.1</a></li> 
    3260                         <li><em>Section 6.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.4">3.1</a></li> 
     3309                        <li><em>Section 6.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.2">3.2</a></li> 
     3310                        <li><em>Section 6.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.3">3.2</a></li> 
     3311                        <li><em>Section 6.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.4">3.2</a></li> 
    32613312                        <li><em>Section 6.7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.6">6.5</a>, <a href="#rfc.xref.Part3.9">8.4</a></li> 
    32623313                     </ul> 
    32633314                  </li> 
    3264                   <li><em>Part4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.1">3.1</a>, <a href="#rfc.xref.Part4.2">3.1</a>, <a href="#rfc.xref.Part4.3">3.1</a>, <a href="#rfc.xref.Part4.4">3.1</a>, <a href="#rfc.xref.Part4.5">3.2</a>, <a href="#rfc.xref.Part4.6">4.1</a>, <a href="#rfc.xref.Part4.7">4.1</a>, <a href="#rfc.xref.Part4.8">4.1</a>, <a href="#rfc.xref.Part4.9">7.2.2</a>, <a href="#rfc.xref.Part4.10">7.3.5</a>, <a href="#rfc.xref.Part4.11">7.4.13</a>, <a href="#Part4"><b>12.1</b></a>, <a href="#rfc.xref.Part4.12">C.2</a><ul> 
    3265                         <li><em>Section 2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.5">3.2</a>, <a href="#rfc.xref.Part4.9">7.2.2</a></li> 
    3266                         <li><em>Section 3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.1">3.1</a></li> 
    3267                         <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.3">3.1</a></li> 
    3268                         <li><em>Section 3.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.2">3.1</a></li> 
    3269                         <li><em>Section 3.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.4">3.1</a></li> 
     3315                  <li><em>Part4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.1">3.2</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">3.2</a>, <a href="#rfc.xref.Part4.5">3.3</a>, <a href="#rfc.xref.Part4.6">4.1</a>, <a href="#rfc.xref.Part4.7">4.1</a>, <a href="#rfc.xref.Part4.8">4.1</a>, <a href="#rfc.xref.Part4.9">7.2.2</a>, <a href="#rfc.xref.Part4.10">7.3.5</a>, <a href="#rfc.xref.Part4.11">7.4.13</a>, <a href="#Part4"><b>12.1</b></a>, <a href="#rfc.xref.Part4.12">C.2</a><ul> 
     3316                        <li><em>Section 2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.5">3.3</a>, <a href="#rfc.xref.Part4.9">7.2.2</a></li> 
     3317                        <li><em>Section 3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.1">3.2</a></li> 
     3318                        <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.3">3.2</a></li> 
     3319                        <li><em>Section 3.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.2">3.2</a></li> 
     3320                        <li><em>Section 3.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.4">3.2</a></li> 
    32703321                        <li><em>Section 4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.6">4.1</a></li> 
    32713322                        <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.7">4.1</a>, <a href="#rfc.xref.Part4.10">7.3.5</a></li> 
     
    32733324                     </ul> 
    32743325                  </li> 
    3275                   <li><em>Part5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.1">3.1</a>, <a href="#rfc.xref.Part5.2">3.1</a>, <a href="#rfc.xref.Part5.3">3.2</a>, <a href="#rfc.xref.Part5.4">4.1</a>, <a href="#rfc.xref.Part5.5">4.1</a>, <a href="#rfc.xref.Part5.6">4.1</a>, <a href="#rfc.xref.Part5.7">6.3</a>, <a href="#rfc.xref.Part5.8">7.2.7</a>, <a href="#rfc.xref.Part5.9">7.4.17</a>, <a href="#rfc.xref.Part5.10">7.4.17</a>, <a href="#Part5"><b>12.1</b></a><ul> 
     3326                  <li><em>Part5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.1">3.2</a>, <a href="#rfc.xref.Part5.2">3.2</a>, <a href="#rfc.xref.Part5.3">3.3</a>, <a href="#rfc.xref.Part5.4">4.1</a>, <a href="#rfc.xref.Part5.5">4.1</a>, <a href="#rfc.xref.Part5.6">4.1</a>, <a href="#rfc.xref.Part5.7">6.3</a>, <a href="#rfc.xref.Part5.8">7.2.7</a>, <a href="#rfc.xref.Part5.9">7.4.17</a>, <a href="#rfc.xref.Part5.10">7.4.17</a>, <a href="#Part5"><b>12.1</b></a><ul> 
    32763327                        <li><em>Section 3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.4">4.1</a></li> 
    32773328                        <li><em>Section 3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.5">4.1</a>, <a href="#rfc.xref.Part5.8">7.2.7</a></li> 
    32783329                        <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.6">4.1</a>, <a href="#rfc.xref.Part5.10">7.4.17</a></li> 
    3279                         <li><em>Section 5.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.3">3.2</a></li> 
    3280                         <li><em>Section 5.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.1">3.1</a></li> 
    3281                         <li><em>Section 5.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.2">3.1</a>, <a href="#rfc.xref.Part5.7">6.3</a>, <a href="#rfc.xref.Part5.9">7.4.17</a></li> 
     3330                        <li><em>Section 5.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.3">3.3</a></li> 
     3331                        <li><em>Section 5.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.1">3.2</a></li> 
     3332                        <li><em>Section 5.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.2">3.2</a>, <a href="#rfc.xref.Part5.7">6.3</a>, <a href="#rfc.xref.Part5.9">7.4.17</a></li> 
    32823333                     </ul> 
    32833334                  </li> 
    3284                   <li><em>Part6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">2.2.1</a>, <a href="#rfc.xref.Part6.2">3.2</a>, <a href="#rfc.xref.Part6.3">3.2</a>, <a href="#rfc.xref.Part6.4">4.2.1</a>, <a href="#rfc.xref.Part6.5">6.3</a>, <a href="#rfc.xref.Part6.6">6.4</a>, <a href="#rfc.xref.Part6.7">6.5</a>, <a href="#rfc.xref.Part6.8">6.6</a>, <a href="#rfc.xref.Part6.9">6.7</a>, <a href="#rfc.xref.Part6.10">7.2.1</a>, <a href="#rfc.xref.Part6.11">7.2.4</a>, <a href="#rfc.xref.Part6.12">7.2.4</a>, <a href="#rfc.xref.Part6.13">7.2.4</a>, <a href="#rfc.xref.Part6.14">7.2.7</a>, <a href="#rfc.xref.Part6.15">7.3.1</a>, <a href="#rfc.xref.Part6.16">7.3.2</a>, <a href="#rfc.xref.Part6.17">7.4.11</a>, <a href="#Part6"><b>12.1</b></a><ul> 
    3285                         <li><em>Section 2.3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.7">6.5</a></li> 
    3286                         <li><em>Section 2.3.1.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.10">7.2.1</a>, <a href="#rfc.xref.Part6.13">7.2.4</a>, <a href="#rfc.xref.Part6.14">7.2.7</a>, <a href="#rfc.xref.Part6.15">7.3.1</a>, <a href="#rfc.xref.Part6.16">7.3.2</a>, <a href="#rfc.xref.Part6.17">7.4.11</a></li> 
    3287                         <li><em>Section 2.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.8">6.6</a>, <a href="#rfc.xref.Part6.9">6.7</a></li> 
    3288                         <li><em>Section 3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.2">3.2</a></li> 
    3289                         <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.11">7.2.4</a></li> 
    3290                         <li><em>Section 3.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.3">3.2</a></li> 
    3291                         <li><em>Section 3.6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.12">7.2.4</a></li> 
     3335                  <li><em>Part6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">2.2.1</a>, <a href="#rfc.xref.Part6.2">3.1</a>, <a href="#rfc.xref.Part6.3">3.3</a>, <a href="#rfc.xref.Part6.4">3.3</a>, <a href="#rfc.xref.Part6.5">4.2.1</a>, <a href="#rfc.xref.Part6.6">6.3</a>, <a href="#rfc.xref.Part6.7">6.4</a>, <a href="#rfc.xref.Part6.8">6.5</a>, <a href="#rfc.xref.Part6.9">6.6</a>, <a href="#rfc.xref.Part6.10">6.7</a>, <a href="#rfc.xref.Part6.11">7.2.1</a>, <a href="#rfc.xref.Part6.12">7.2.4</a>, <a href="#rfc.xref.Part6.13">7.2.4</a>, <a href="#rfc.xref.Part6.14">7.2.4</a>, <a href="#rfc.xref.Part6.15">7.2.7</a>, <a href="#rfc.xref.Part6.16">7.3.1</a>, <a href="#rfc.xref.Part6.17">7.3.2</a>, <a href="#rfc.xref.Part6.18">7.4.11</a>, <a href="#Part6"><b>12.1</b></a><ul> 
     3336                        <li><em>Section 2.3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.8">6.5</a></li> 
     3337                        <li><em>Section 2.3.1.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.11">7.2.1</a>, <a href="#rfc.xref.Part6.14">7.2.4</a>, <a href="#rfc.xref.Part6.15">7.2.7</a>, <a href="#rfc.xref.Part6.16">7.3.1</a>, <a href="#rfc.xref.Part6.17">7.3.2</a>, <a href="#rfc.xref.Part6.18">7.4.11</a></li> 
     3338                        <li><em>Section 2.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.9">6.6</a>, <a href="#rfc.xref.Part6.10">6.7</a></li> 
     3339                        <li><em>Section 3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.3">3.3</a></li> 
     3340                        <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.12">7.2.4</a></li> 
     3341                        <li><em>Section 3.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.4">3.3</a></li> 
     3342                        <li><em>Section 3.6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.13">7.2.4</a></li> 
    32923343                     </ul> 
    32933344                  </li> 
    3294                   <li><em>Part7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.1">3.1</a>, <a href="#rfc.xref.Part7.2">3.1</a>, <a href="#rfc.xref.Part7.3">3.2</a>, <a href="#rfc.xref.Part7.4">3.2</a>, <a href="#rfc.xref.Part7.5">4.1</a>, <a href="#rfc.xref.Part7.6">4.1</a>, <a href="#rfc.xref.Part7.7">4.1</a>, <a href="#rfc.xref.Part7.8">7.4.2</a>, <a href="#rfc.xref.Part7.9">7.4.8</a>, <a href="#Part7"><b>12.1</b></a><ul> 
     3345                  <li><em>Part7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.1">3.2</a>, <a href="#rfc.xref.Part7.2">3.2</a>, <a href="#rfc.xref.Part7.3">3.3</a>, <a href="#rfc.xref.Part7.4">3.3</a>, <a href="#rfc.xref.Part7.5">4.1</a>, <a href="#rfc.xref.Part7.6">4.1</a>, <a href="#rfc.xref.Part7.7">4.1</a>, <a href="#rfc.xref.Part7.8">7.4.2</a>, <a href="#rfc.xref.Part7.9">7.4.8</a>, <a href="#Part7"><b>12.1</b></a><ul> 
    32953346                        <li><em>Section 3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.5">4.1</a></li> 
    32963347                        <li><em>Section 3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.6">4.1</a>, <a href="#rfc.xref.Part7.8">7.4.2</a></li> 
    32973348                        <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.7">4.1</a>, <a href="#rfc.xref.Part7.9">7.4.8</a></li> 
    3298                         <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.1">3.1</a></li> 
    3299                         <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.3">3.2</a></li> 
    3300                         <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.2">3.1</a></li> 
    3301                         <li><em>Section 4.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.4">3.2</a></li> 
     3349                        <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.1">3.2</a></li> 
     3350                        <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.3">3.3</a></li> 
     3351                        <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.2">3.2</a></li> 
     3352                        <li><em>Section 4.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.4">3.3</a></li> 
    33023353                     </ul> 
    33033354                  </li> 
     
    33073358            </li> 
    33083359            <li><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul> 
    3309                   <li>Referer header field&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">3.1</a>, <a href="#rfc.iref.r.1"><b>8.6</b></a>, <a href="#rfc.xref.header.referer.2">9.3</a>, <a href="#rfc.xref.header.referer.3">A</a></li> 
    3310                   <li>Retry-After header field&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">3.2</a>, <a href="#rfc.xref.header.retry-after.2">7.5.4</a>, <a href="#rfc.iref.r.2"><b>8.7</b></a>, <a href="#rfc.xref.header.retry-after.3">9.3</a></li> 
     3360                  <li>Referer header field&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">3.2</a>, <a href="#rfc.iref.r.1"><b>8.6</b></a>, <a href="#rfc.xref.header.referer.2">9.3</a>, <a href="#rfc.xref.header.referer.3">A</a></li> 
     3361                  <li>Retry-After header field&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">3.3</a>, <a href="#rfc.xref.header.retry-after.2">7.5.4</a>, <a href="#rfc.iref.r.2"><b>8.7</b></a>, <a href="#rfc.xref.header.retry-after.3">9.3</a></li> 
    33113362                  <li><em>RFC1945</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC1945.1">7.3.3</a>, <a href="#RFC1945"><b>12.2</b></a><ul> 
    33123363                        <li><em>Section 9.3</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC1945.1">7.3.3</a></li> 
     
    33273378                     </ul> 
    33283379                  </li> 
    3329                   <li><em>RFC3864</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3864.1">9.3</a>, <a href="#RFC3864"><b>12.2</b></a></li> 
     3380                  <li><em>RFC3864</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3864.1">3.1</a>, <a href="#rfc.xref.RFC3864.2">3.1</a>, <a href="#rfc.xref.RFC3864.3">9.3</a>, <a href="#RFC3864"><b>12.2</b></a><ul> 
     3381                        <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3864.2">3.1</a></li> 
     3382                     </ul> 
     3383                  </li> 
    33303384                  <li><em>RFC3986</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">8.4</a>, <a href="#rfc.xref.RFC3986.2">8.4</a>, <a href="#RFC3986"><b>12.1</b></a><ul> 
    33313385                        <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">8.4</a></li> 
     
    33373391                     </ul> 
    33383392                  </li> 
    3339                   <li><em>RFC5234</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5234.1">1.2</a>, <a href="#rfc.xref.RFC5234.2">1.2</a>, <a href="#RFC5234"><b>12.1</b></a><ul> 
     3393                  <li><em>RFC5234</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5234.1">1.2</a>, <a href="#rfc.xref.RFC5234.2">1.2</a>, <a href="#rfc.xref.RFC5234.3">3.1</a>, <a href="#RFC5234"><b>12.1</b></a><ul> 
    33403394                        <li><em>Appendix B.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5234.2">1.2</a></li> 
    33413395                     </ul> 
     
    33463400                  </li> 
    33473401                  <li><em>RFC5789</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5789.1">6.6</a>, <a href="#RFC5789"><b>12.2</b></a></li> 
     3402                  <li><em>RFC5987</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5987.1">3.1</a>, <a href="#RFC5987"><b>12.2</b></a></li> 
    33483403               </ul> 
    33493404            </li> 
    33503405            <li><a id="rfc.index.S" href="#rfc.index.S"><b>S</b></a><ul> 
    33513406                  <li>Safe Methods&nbsp;&nbsp;<a href="#rfc.iref.s.1"><b>6.1.1</b></a></li> 
    3352                   <li>Server header field&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">3.2</a>, <a href="#rfc.iref.s.44"><b>8.8</b></a>, <a href="#rfc.xref.header.server.2">9.3</a>, <a href="#rfc.xref.header.server.3">10.1</a>, <a href="#rfc.xref.header.server.4">A</a></li> 
     3407                  <li>Server header field&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">3.3</a>, <a href="#rfc.iref.s.44"><b>8.8</b></a>, <a href="#rfc.xref.header.server.2">9.3</a>, <a href="#rfc.xref.header.server.3">10.1</a>, <a href="#rfc.xref.header.server.4">A</a></li> 
    33533408                  <li>Status Codes&nbsp;&nbsp; 
    33543409                     <ul> 
     
    34043459            </li> 
    34053460            <li><a id="rfc.index.U" href="#rfc.index.U"><b>U</b></a><ul> 
    3406                   <li>User-Agent header field&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">3.1</a>, <a href="#rfc.iref.u.1"><b>8.9</b></a>, <a href="#rfc.xref.header.user-agent.2">9.3</a>, <a href="#rfc.xref.header.user-agent.3">10.1</a></li> 
     3461                  <li>User-Agent header field&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">3.2</a>, <a href="#rfc.iref.u.1"><b>8.9</b></a>, <a href="#rfc.xref.header.user-agent.2">9.3</a>, <a href="#rfc.xref.header.user-agent.3">10.1</a></li> 
    34073462               </ul> 
    34083463            </li> 
  • draft-ietf-httpbis/latest/p2-semantics.xml

    r1416 r1417  
    3131  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
    3232  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
     33  <!ENTITY chunked-encoding           "<xref target='Part1' x:rel='#chunked.encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
    3334  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
    3435  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
     
    4546  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
    4647  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
     48  <!ENTITY header-connection          "<xref target='Part1' x:rel='#header.connection' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
    4749  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
    4850  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 
     
    480482 
    481483<section title="Header Fields" anchor="header.fields"> 
     484<t> 
     485   Header fields are key value pairs that can be used to communicate data about 
     486   the message, its payload, the target resource, or about the connection 
     487   itself (i.e., control data).  See &header-fields; for a general definition 
     488   of their syntax. 
     489</t> 
     490 
     491<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields"> 
     492<t> 
     493   New header fields are registered using the procedures described in 
     494   <xref target="RFC3864"/>. 
     495</t> 
     496<t> 
     497   The requirements for header field names are defined in 
     498   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications 
     499   defining new fields are advised to keep the name as short as practical, and 
     500   not to prefix them with "X-" if they are to be registered (either 
     501   immediately or in the future). 
     502</t> 
     503<t> 
     504   New header field values typically have their syntax defined using ABNF 
     505   (<xref target="RFC5234"/>), using the extensions defined in &notation-abnf; 
     506   as necessary, and are usually constrained to the range of ASCII characters. 
     507   Header fields needing a greater range of characters can use an encoding 
     508   such as the one defined in <xref target="RFC5987"/>.  
     509</t> 
     510<t> 
     511   Because commas (",") are used as a generic delimiter between field-values, 
     512   they need to be treated with care if they are allowed in the field-value's 
     513   payload. Typically, components that might contain a comma are protected with 
     514   double-quotes using the quoted-string ABNF production (&field-rules;).  
     515</t> 
     516<t> 
     517   For example, a textual date and a URI (either of which might contain a comma) 
     518   could be safely carried in field-values like these: 
     519</t> 
     520<figure><artwork type="example"> 
     521  Example-URI-Field: "http://example.com/a.html,foo", 
     522                     "http://without-a-comma.example.com/" 
     523  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005" 
     524</artwork></figure> 
     525<t> 
     526   Authors of specifications defining new header fields are advised to consider 
     527   documenting: 
     528  <list style="symbols"> 
     529    <t>Whether the field is a single value, or whether it can be a list 
     530    (delimited by commas; see &header-fields;).</t> 
     531    <t>Under what conditions the header field can be used; e.g., only i 
     532    responses or requests, in all messages, only on responses to a particular 
     533    request method.</t> 
     534    <t>Whether it is appropriate to list the field-name in the Connection header 
     535    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t> 
     536    <t>Under what conditions intermediaries are allowed to modify the header 
     537    field's value, insert or delete it.</t> 
     538    <t>How the header might interact with caching (see <xref target="Part6"/>).</t> 
     539    <t>Whether the header field is useful or allowable in trailers (see 
     540    &chunked-encoding;).</t> 
     541    <t>Whether the header field should be preserved across redirects.</t> 
     542  </list> 
     543</t> 
     544</section> 
    482545 
    483546<section title="Request Header Fields" anchor="request.header.fields"> 
     
    35053568</reference> 
    35063569 
     3570<reference anchor="RFC5987"> 
     3571        <front> 
     3572    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title> 
     3573    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke"> 
     3574      <organization abbrev="greenbytes">greenbytes GmbH</organization> 
     3575      <address> 
     3576        <postal> 
     3577          <street>Hafenweg 16</street> 
     3578          <city>Muenster</city><region>NW</region><code>48155</code> 
     3579          <country>Germany</country> 
     3580        </postal> 
     3581        <email>julian.reschke@greenbytes.de</email>      
     3582        <uri>http://greenbytes.de/tech/webdav/</uri>     
     3583      </address> 
     3584    </author> 
     3585    <date month="August" year="2010"/> 
     3586  </front> 
     3587  <seriesInfo name="RFC" value="5987"/> 
     3588</reference> 
     3589 
    35073590</references> 
    35083591 
     
    41844267<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16"> 
    41854268<t> 
    4186   None yet. 
     4269  Work-in-progress: 
     4270  <list style="symbols">  
     4271    <t> 
     4272      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>: 
     4273      "Considerations for new headers" 
     4274    </t> 
     4275  </list> 
    41874276</t> 
    41884277</section> 
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