Changeset 2339


Ignore:
Timestamp:
Aug 1, 2013, 7:59:29 PM (6 years ago)
Author:
fielding@…
Message:

(editorial) Partition the definition of chunked trailer part and the Trailer header field into separate sections

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

Legend:

Unmodified
Added
Removed

  • draft-ietf-httpbis/latest/p1-messaging.html

    r2338 r2339  
    616616         <li><a href="#rfc.section.4">4.</a>&nbsp;&nbsp;&nbsp;<a href="#transfer.codings">Transfer Codings</a><ul>
    617617               <li><a href="#rfc.section.4.1">4.1</a>&nbsp;&nbsp;&nbsp;<a href="#chunked.encoding">Chunked Transfer Coding</a><ul>
    618                      <li><a href="#rfc.section.4.1.1">4.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#header.trailer">Trailer</a></li>
    619                      <li><a href="#rfc.section.4.1.2">4.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#decoding.chunked">Decoding chunked</a></li>
     618                     <li><a href="#rfc.section.4.1.1">4.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#chunked.trailer.part">Chunked Trailer Part</a></li>
     619                     <li><a href="#rfc.section.4.1.2">4.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#decoding.chunked">Decoding Chunked</a></li>
    620620                  </ul>
    621621               </li>
    … …  
    627627               </li>
    628628               <li><a href="#rfc.section.4.3">4.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.te">TE</a></li>
     629               <li><a href="#rfc.section.4.4">4.4</a>&nbsp;&nbsp;&nbsp;<a href="#header.trailer">Trailer</a></li>
    629630            </ul>
    630631         </li>
    … …  
    15971598      <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.64"></span><span id="rfc.iref.g.65"></span><span id="rfc.iref.g.66"></span><span id="rfc.iref.g.67"></span><span id="rfc.iref.g.68"></span><span id="rfc.iref.g.69"></span><span id="rfc.iref.g.70"></span><span id="rfc.iref.g.71"></span><span id="rfc.iref.g.72"></span><span id="rfc.iref.g.73"></span><span id="rfc.iref.g.74"></span>  <a href="#chunked.encoding" class="smpl">chunked-body</a>   = *<a href="#chunked.encoding" class="smpl">chunk</a>
    15981599                   <a href="#chunked.encoding" class="smpl">last-chunk</a>
    1599                    <a href="#chunked.encoding" class="smpl">trailer-part</a>
     1600                   <a href="#chunked.trailer.part" class="smpl">trailer-part</a>
    16001601                   <a href="#core.rules" class="smpl">CRLF</a>
    16011602 
    … …  
    16091610  <a href="#chunked.encoding" class="smpl">chunk-ext-val</a>  = <a href="#rule.token.separators" class="smpl">token</a> / <a href="#chunked.encoding" class="smpl">quoted-str-nf</a>
    16101611  <a href="#chunked.encoding" class="smpl">chunk-data</a>     = 1*<a href="#core.rules" class="smpl">OCTET</a> ; a sequence of chunk-size octets
    1611   <a href="#chunked.encoding" class="smpl">trailer-part</a>   = *( <a href="#header.fields" class="smpl">header-field</a> <a href="#core.rules" class="smpl">CRLF</a> )
    16121612 
    16131613  <a href="#chunked.encoding" class="smpl">quoted-str-nf</a>  = <a href="#core.rules" class="smpl">DQUOTE</a> *( <a href="#chunked.encoding" class="smpl">qdtext-nf</a> / <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> ) <a href="#core.rules" class="smpl">DQUOTE</a>
    … …  
    16201620         an empty line.
    16211621      </p>
    1622       <div id="rfc.iref.t.5"></div>
    1623       <h3 id="rfc.section.4.1.1"><a href="#rfc.section.4.1.1">4.1.1</a>&nbsp;<a id="header.trailer" href="#header.trailer">Trailer</a></h3>
     1622      <h3 id="rfc.section.4.1.1"><a href="#rfc.section.4.1.1">4.1.1</a>&nbsp;<a id="chunked.trailer.part" href="#chunked.trailer.part">Chunked Trailer Part</a></h3>
    16241623      <p id="rfc.section.4.1.1.p.1">A trailer allows the sender to include additional fields at the end of a chunked message in order to supply metadata that
    16251624         might be dynamically generated while the message body is sent, such as a message integrity check, digital signature, or post-processing
    … …  
    16271626         header block.
    16281627      </p>
    1629       <p id="rfc.section.4.1.1.p.2">When a message includes a message body encoded with the chunked transfer coding and the sender desires to send metadata in
    1630          the form of trailer fields at the end of the message, the sender <em class="bcp14">SHOULD</em> generate a <a href="#header.trailer" class="smpl">Trailer</a> header field before the message body to indicate which fields will be present in the trailers. This allows the recipient to
    1631          prepare for receipt of that metadata before it starts processing the body, which is useful if the message is being streamed
    1632          and the recipient wishes to confirm an integrity check on the fly.
    1633       </p>
    1634       <div id="rfc.figure.u.33"></div><pre class="inline"><span id="rfc.iref.g.75"></span>  <a href="#header.trailer" class="smpl">Trailer</a> = 1#<a href="#header.fields" class="smpl">field-name</a>
    1635 </pre><p id="rfc.section.4.1.1.p.4">A sender <em class="bcp14">MUST NOT</em> generate a trailer that contains a field which needs to be known by the recipient before it can begin processing the message
     1628      <div id="rfc.figure.u.33"></div><pre class="inline"><span id="rfc.iref.g.75"></span>  <a href="#chunked.trailer.part" class="smpl">trailer-part</a>   = *( <a href="#header.fields" class="smpl">header-field</a> <a href="#core.rules" class="smpl">CRLF</a> )
     1629</pre><p id="rfc.section.4.1.1.p.3">A sender <em class="bcp14">MUST NOT</em> generate a trailer that contains a field which needs to be known by the recipient before it can begin processing the message
    16361630         body. For example, most recipients need to know the values of <a href="p2-semantics.html#header.content-encoding" class="smpl">Content-Encoding</a> and <a href="p2-semantics.html#header.content-type" class="smpl">Content-Type</a> in order to select a content handler, so placing those fields in a trailer would force the recipient to buffer the entire
    16371631         body before it could begin, greatly increasing user-perceived latency and defeating one of the main advantages of using chunked
    16381632         to send data streams of unknown length. A sender <em class="bcp14">MUST NOT</em> generate a trailer containing a <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a>, <a href="#header.content-length" class="smpl">Content-Length</a>, or <a href="#header.trailer" class="smpl">Trailer</a> field.
    16391633      </p>
    1640       <p id="rfc.section.4.1.1.p.5">A server <em class="bcp14">MUST</em> generate an empty trailer with the chunked transfer coding unless at least one of the following is true:
     1634      <p id="rfc.section.4.1.1.p.4">A server <em class="bcp14">MUST</em> generate an empty trailer with the chunked transfer coding unless at least one of the following is true:
    16411635      </p>
    16421636      <ol>
    … …  
    16481642         </li>
    16491643      </ol>
    1650       <p id="rfc.section.4.1.1.p.6">The above requirement prevents the need for an infinite buffer when a message is being received by an HTTP/1.1 (or later)
     1644      <p id="rfc.section.4.1.1.p.5">The above requirement prevents the need for an infinite buffer when a message is being received by an HTTP/1.1 (or later)
    16511645         proxy and forwarded to an HTTP/1.0 recipient.
    16521646      </p>
    1653       <h3 id="rfc.section.4.1.2"><a href="#rfc.section.4.1.2">4.1.2</a>&nbsp;<a id="decoding.chunked" href="#decoding.chunked">Decoding chunked</a></h3>
     1647      <h3 id="rfc.section.4.1.2"><a href="#rfc.section.4.1.2">4.1.2</a>&nbsp;<a id="decoding.chunked" href="#decoding.chunked">Decoding Chunked</a></h3>
    16541648      <p id="rfc.section.4.1.2.p.1">A process for decoding the chunked transfer coding can be represented in pseudo-code as:</p>
    16551649      <div id="rfc.figure.u.34"></div><pre class="text">  length := 0
    … …  
    16891683      <p id="rfc.section.4.2.3.p.1">The "gzip" coding is an LZ77 coding with a 32 bit CRC that is commonly produced by the gzip file compression program <a href="#RFC1952" id="rfc.xref.RFC1952.1"><cite title="GZIP file format specification version 4.3">[RFC1952]</cite></a>. Recipients <em class="bcp14">SHOULD</em> consider "x-gzip" to be equivalent to "gzip".
    16901684      </p>
    1691       <div id="rfc.iref.t.6"></div>
     1685      <div id="rfc.iref.t.5"></div>
    16921686      <h2 id="rfc.section.4.3"><a href="#rfc.section.4.3">4.3</a>&nbsp;<a id="header.te" href="#header.te">TE</a></h2>
    16931687      <p id="rfc.section.4.3.p.1">The "TE" header field in a request indicates what transfer codings, besides chunked, the client is willing to accept in response,
    … …  
    17071701  TE: trailers, deflate;q=0.5
    17081702</pre><p id="rfc.section.4.3.p.6">The presence of the keyword "trailers" indicates that the client is willing to accept trailer fields in a chunked transfer
    1709          coding, as defined in <a href="#chunked.encoding" title="Chunked Transfer Coding">Section&nbsp;4.1</a>, on behalf of itself and any downstream clients. For requests from an intermediary, this implies that either: (a) all downstream
     1703         coding, as defined in <a href="#chunked.trailer.part" title="Chunked Trailer Part">Section&nbsp;4.1.1</a>, on behalf of itself and any downstream clients. For requests from an intermediary, this implies that either: (a) all downstream
    17101704         clients are willing to accept trailer fields in the forwarded response; or, (b) the intermediary will attempt to buffer the
    17111705         response on behalf of downstream recipients. Note that HTTP/1.1 does not define any means to limit the size of a chunked response
    … …  
    17211715      <p id="rfc.section.4.3.p.9">Since the TE header field only applies to the immediate connection, a sender of TE <em class="bcp14">MUST</em> also send a "TE" connection option within the <a href="#header.connection" class="smpl">Connection</a> header field (<a href="#header.connection" id="rfc.xref.header.connection.2" title="Connection">Section&nbsp;6.1</a>) in order to prevent the TE field from being forwarded by intermediaries that do not support its semantics.
    17221716      </p>
    1723       <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a id="message.routing" href="#message.routing">Message Routing</a></h1>
     1717      <div id="rfc.iref.t.6"></div>
     1718      <h2 id="rfc.section.4.4"><a href="#rfc.section.4.4">4.4</a>&nbsp;<a id="header.trailer" href="#header.trailer">Trailer</a></h2>
     1719      <p id="rfc.section.4.4.p.1">When a message includes a message body encoded with the chunked transfer coding and the sender desires to send metadata in
     1720         the form of trailer fields at the end of the message, the sender <em class="bcp14">SHOULD</em> generate a <a href="#header.trailer" class="smpl">Trailer</a> header field before the message body to indicate which fields will be present in the trailers. This allows the recipient to
     1721         prepare for receipt of that metadata before it starts processing the body, which is useful if the message is being streamed
     1722         and the recipient wishes to confirm an integrity check on the fly.
     1723      </p>
     1724      <div id="rfc.figure.u.37"></div><pre class="inline"><span id="rfc.iref.g.81"></span>  <a href="#header.trailer" class="smpl">Trailer</a> = 1#<a href="#header.fields" class="smpl">field-name</a>
     1725</pre><h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a id="message.routing" href="#message.routing">Message Routing</a></h1>
    17241726      <p id="rfc.section.5.p.1">HTTP request message routing is determined by each client based on the target resource, the client's proxy configuration,
    17251727         and establishment or reuse of an inbound connection. The corresponding response routing follows the same connection chain
    … …  
    17591761         both the method being requested and whether the request is to a proxy.
    17601762      </p>
    1761       <div id="rfc.figure.u.37"></div><pre class="inline"><span id="rfc.iref.g.81"></span><span id="rfc.iref.g.82"></span><span id="rfc.iref.g.83"></span><span id="rfc.iref.g.84"></span><span id="rfc.iref.g.85"></span>  <a href="#request-target" class="smpl">request-target</a> = <a href="#origin-form" class="smpl">origin-form</a>
     1763      <div id="rfc.figure.u.38"></div><pre class="inline"><span id="rfc.iref.g.82"></span><span id="rfc.iref.g.83"></span><span id="rfc.iref.g.84"></span><span id="rfc.iref.g.85"></span><span id="rfc.iref.g.86"></span>  <a href="#request-target" class="smpl">request-target</a> = <a href="#origin-form" class="smpl">origin-form</a>
    17621764                 / <a href="#absolute-form" class="smpl">absolute-form</a>
    17631765                 / <a href="#authority-form" class="smpl">authority-form</a>
    … …  
    17771779      </p>
    17781780      <p id="rfc.section.5.3.p.5">For example, a client wishing to retrieve a representation of the resource identified as</p>
    1779       <div id="rfc.figure.u.38"></div><pre class="text">http://www.example.org/where?q=now
     1781      <div id="rfc.figure.u.39"></div><pre class="text">http://www.example.org/where?q=now
    17801782</pre><p id="rfc.section.5.3.p.7">directly from the origin server would open (or reuse) a TCP connection to port 80 of the host "www.example.org" and send the
    17811783         lines:
    17821784      </p>
    1783       <div id="rfc.figure.u.39"></div><pre class="text2">GET /where?q=now HTTP/1.1
     1785      <div id="rfc.figure.u.40"></div><pre class="text2">GET /where?q=now HTTP/1.1
    17841786Host: www.example.org
    17851787</pre><p id="rfc.section.5.3.p.9">followed by the remainder of the request message.</p>
    … …  
    17931795      </p>
    17941796      <p id="rfc.section.5.3.p.12">An example absolute-form of request-line would be:</p>
    1795       <div id="rfc.figure.u.40"></div><pre class="text2">GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
     1797      <div id="rfc.figure.u.41"></div><pre class="text2">GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
    17961798</pre><p id="rfc.section.5.3.p.14">To allow for transition to the absolute-form for all requests in some future version of HTTP, HTTP/1.1 servers <em class="bcp14">MUST</em> accept the absolute-form in requests, even though HTTP/1.1 clients will only send them in requests to proxies.
    17971799      </p>
    … …  
    18021804      <p id="rfc.section.5.3.p.16">The <dfn>authority-form</dfn> of request-target is only used for CONNECT requests (<a href="p2-semantics.html#CONNECT" title="CONNECT">Section 4.3.6</a> of <a href="#Part2" id="rfc.xref.Part2.19"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content">[Part2]</cite></a>). When making a CONNECT request to establish a tunnel through one or more proxies, a client <em class="bcp14">MUST</em> send only the target URI's authority component (excluding any userinfo and its "@" delimiter) as the request-target. For example,
    18031805      </p>
    1804       <div id="rfc.figure.u.41"></div><pre class="text2">CONNECT www.example.com:80 HTTP/1.1
     1806      <div id="rfc.figure.u.42"></div><pre class="text2">CONNECT www.example.com:80 HTTP/1.1
    18051807</pre><div id="asterisk-form">
    18061808         <p id="rfc.section.5.3.p.18"><span id="rfc.iref.a.4"></span> <b>asterisk-form</b>
    … …  
    18101812         the client <em class="bcp14">MUST</em> send only "*" (%x2A) as the request-target. For example,
    18111813      </p>
    1812       <div id="rfc.figure.u.42"></div><pre class="text2">OPTIONS * HTTP/1.1
     1814      <div id="rfc.figure.u.43"></div><pre class="text2">OPTIONS * HTTP/1.1
    18131815</pre><p id="rfc.section.5.3.p.21">If a proxy receives an OPTIONS request with an absolute-form of request-target in which the URI has an empty path and no query
    18141816         component, then the last proxy on the request chain <em class="bcp14">MUST</em> send a request-target of "*" when it forwards the request to the indicated origin server.
    18151817      </p>
    1816       <div id="rfc.figure.u.43"></div>
     1818      <div id="rfc.figure.u.44"></div>
    18171819      <p>For example, the request</p><pre class="text2">OPTIONS http://www.example.org:8001 HTTP/1.1
    1818 </pre><div id="rfc.figure.u.44"></div>
     1820</pre><div id="rfc.figure.u.45"></div>
    18191821      <p>would be forwarded by the final proxy as</p><pre class="text2">OPTIONS * HTTP/1.1
    18201822Host: www.example.org:8001
    … …  
    18251827         to distinguish among resources while servicing requests for multiple host names on a single IP address.
    18261828      </p>
    1827       <div id="rfc.figure.u.45"></div><pre class="inline"><span id="rfc.iref.g.86"></span>  <a href="#header.host" class="smpl">Host</a> = <a href="#uri" class="smpl">uri-host</a> [ ":" <a href="#uri" class="smpl">port</a> ] ; <a href="#http.uri" title="http URI scheme">Section&nbsp;2.7.1</a>
     1829      <div id="rfc.figure.u.46"></div><pre class="inline"><span id="rfc.iref.g.87"></span>  <a href="#header.host" class="smpl">Host</a> = <a href="#uri" class="smpl">uri-host</a> [ ":" <a href="#uri" class="smpl">port</a> ] ; <a href="#http.uri" title="http URI scheme">Section&nbsp;2.7.1</a>
    18281830</pre><p id="rfc.section.5.4.p.3">A client <em class="bcp14">MUST</em> send a Host header field in all HTTP/1.1 request messages. If the target URI includes an authority component, then a client <em class="bcp14">MUST</em> send a field-value for Host that is identical to that authority component, excluding any userinfo subcomponent and its "@"
    18291831         delimiter (<a href="#http.uri" title="http URI scheme">Section&nbsp;2.7.1</a>). If the authority component is missing or undefined for the target URI, then a client <em class="bcp14">MUST</em> send a Host header field with an empty field-value.
    … …  
    18321834      </p>
    18331835      <p id="rfc.section.5.4.p.5">For example, a GET request to the origin server for &lt;http://www.example.org/pub/WWW/&gt; would begin with:</p>
    1834       <div id="rfc.figure.u.46"></div><pre class="text2">GET /pub/WWW/ HTTP/1.1
     1836      <div id="rfc.figure.u.47"></div><pre class="text2">GET /pub/WWW/ HTTP/1.1
    18351837Host: www.example.org
    18361838</pre><p id="rfc.section.5.4.p.7">A client <em class="bcp14">MUST</em> send a Host header field in an HTTP/1.1 request even if the request-target is in the absolute-form, since this allows the
    … …  
    18711873         the scheme, "://", authority, and combined path and query component.
    18721874      </p>
    1873       <div id="rfc.figure.u.47"></div>
     1875      <div id="rfc.figure.u.48"></div>
    18741876      <p>Example 1: the following message received over an insecure TCP connection</p><pre class="text">GET /pub/WWW/TheProject.html HTTP/1.1
    18751877Host: www.example.org:8080
    1876 </pre><div id="rfc.figure.u.48"></div>
     1878</pre><div id="rfc.figure.u.49"></div>
    18771879      <p>has an effective request URI of</p><pre class="text">http://www.example.org:8080/pub/WWW/TheProject.html
    1878 </pre><div id="rfc.figure.u.49"></div>
     1880</pre><div id="rfc.figure.u.50"></div>
    18791881      <p>Example 2: the following message received over a TLS-secured TCP connection</p><pre class="text">OPTIONS * HTTP/1.1
    18801882Host: www.example.org
    1881 </pre><div id="rfc.figure.u.50"></div>
     1883</pre><div id="rfc.figure.u.51"></div>
    18821884      <p>has an effective request URI of</p><pre class="text">https://www.example.org
    18831885</pre><p id="rfc.section.5.5.p.12">An origin server that does not allow resources to differ by requested host <em class="bcp14">MAY</em> ignore the <a href="#header.host" class="smpl">Host</a> field-value and instead replace it with a configured server name when constructing the effective request URI.
    … …  
    19121914         along the request/response chain.
    19131915      </p>
    1914       <div id="rfc.figure.u.51"></div><pre class="inline"><span id="rfc.iref.g.87"></span><span id="rfc.iref.g.88"></span><span id="rfc.iref.g.89"></span><span id="rfc.iref.g.90"></span><span id="rfc.iref.g.91"></span><span id="rfc.iref.g.92"></span>  <a href="#header.via" class="smpl">Via</a> = 1#( <a href="#header.via" class="smpl">received-protocol</a> <a href="#rule.whitespace" class="smpl">RWS</a> <a href="#header.via" class="smpl">received-by</a> [ <a href="#rule.whitespace" class="smpl">RWS</a> <a href="#rule.comment" class="smpl">comment</a> ] )
     1916      <div id="rfc.figure.u.52"></div><pre class="inline"><span id="rfc.iref.g.88"></span><span id="rfc.iref.g.89"></span><span id="rfc.iref.g.90"></span><span id="rfc.iref.g.91"></span><span id="rfc.iref.g.92"></span><span id="rfc.iref.g.93"></span>  <a href="#header.via" class="smpl">Via</a> = 1#( <a href="#header.via" class="smpl">received-protocol</a> <a href="#rule.whitespace" class="smpl">RWS</a> <a href="#header.via" class="smpl">received-by</a> [ <a href="#rule.whitespace" class="smpl">RWS</a> <a href="#rule.comment" class="smpl">comment</a> ] )
    19151917
    19161918  <a href="#header.via" class="smpl">received-protocol</a> = [ <a href="#header.upgrade" class="smpl">protocol-name</a> "/" ] <a href="#header.upgrade" class="smpl">protocol-version</a>
    … …  
    19381940         server at www.example.com. The request received by www.example.com would then have the following Via header field:
    19391941      </p>
    1940       <div id="rfc.figure.u.52"></div><pre class="text">  Via: 1.0 fred, 1.1 p.example.net
     1942      <div id="rfc.figure.u.53"></div><pre class="text">  Via: 1.0 fred, 1.1 p.example.net
    19411943</pre><p id="rfc.section.5.7.1.p.10">An intermediary used as a portal through a network firewall <em class="bcp14">SHOULD NOT</em> forward the names and ports of hosts within the firewall region unless it is explicitly enabled to do so. If not enabled,
    19421944         such an intermediary <em class="bcp14">SHOULD</em> replace each received-by host of any host behind the firewall by an appropriate pseudonym for that host.
    … …  
    19451947         values. For example,
    19461948      </p>
    1947       <div id="rfc.figure.u.53"></div><pre class="text">  Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
     1949      <div id="rfc.figure.u.54"></div><pre class="text">  Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
    19481950</pre><p id="rfc.section.5.7.1.p.13">could be collapsed to</p>
    1949       <div id="rfc.figure.u.54"></div><pre class="text">  Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
     1951      <div id="rfc.figure.u.55"></div><pre class="text">  Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
    19501952</pre><p id="rfc.section.5.7.1.p.15">Senders <em class="bcp14">SHOULD NOT</em> combine multiple entries unless they are all under the same organizational control and the hosts have already been replaced
    19511953         by pseudonyms. Senders <em class="bcp14">MUST NOT</em> combine entries that have different received-protocol values.
    … …  
    20032005      </p>
    20042006      <p id="rfc.section.6.1.p.4">The Connection header field's value has the following grammar:</p>
    2005       <div id="rfc.figure.u.55"></div><pre class="inline"><span id="rfc.iref.g.93"></span><span id="rfc.iref.g.94"></span>  <a href="#header.connection" class="smpl">Connection</a>        = 1#<a href="#header.connection" class="smpl">connection-option</a>
     2007      <div id="rfc.figure.u.56"></div><pre class="inline"><span id="rfc.iref.g.94"></span><span id="rfc.iref.g.95"></span>  <a href="#header.connection" class="smpl">Connection</a>        = 1#<a href="#header.connection" class="smpl">connection-option</a>
    20062008  <a href="#header.connection" class="smpl">connection-option</a> = <a href="#rule.token.separators" class="smpl">token</a>
    20072009</pre><p id="rfc.section.6.1.p.6">Connection options are case-insensitive.</p>
    … …  
    20232025         For example,
    20242026      </p>
    2025       <div id="rfc.figure.u.56"></div><pre class="text">  Connection: close
     2027      <div id="rfc.figure.u.57"></div><pre class="text">  Connection: close
    20262028</pre><p id="rfc.section.6.1.p.12">in either the request or the response header fields indicates that the sender is going to close the connection after the current
    20272029         request/response is complete (<a href="#persistent.tear-down" id="rfc.xref.persistent.tear-down.1" title="Tear-down">Section&nbsp;6.6</a>).
    … …  
    21582160         in order of descending preference, before sending the final response. A server <em class="bcp14">MAY</em> ignore a received Upgrade header field if it wishes to continue using the current protocol on that connection.
    21592161      </p>
    2160       <div id="rfc.figure.u.57"></div><pre class="inline"><span id="rfc.iref.g.95"></span>  <a href="#header.upgrade" class="smpl">Upgrade</a>          = 1#<a href="#header.upgrade" class="smpl">protocol</a>
     2162      <div id="rfc.figure.u.58"></div><pre class="inline"><span id="rfc.iref.g.96"></span>  <a href="#header.upgrade" class="smpl">Upgrade</a>          = 1#<a href="#header.upgrade" class="smpl">protocol</a>
    21612163
    21622164  <a href="#header.upgrade" class="smpl">protocol</a>         = <a href="#header.upgrade" class="smpl">protocol-name</a> ["/" <a href="#header.upgrade" class="smpl">protocol-version</a>]
    … …  
    21722174         in order of descending preference, when appropriate for a future request.
    21732175      </p>
    2174       <div id="rfc.figure.u.58"></div>
     2176      <div id="rfc.figure.u.59"></div>
    21752177      <p>The following is a hypothetical example sent by a client:</p><pre class="text2">GET /hello.txt HTTP/1.1
    21762178Host: www.example.com
    … …  
    21902192         by any protocol.
    21912193      </p>
    2192       <div id="rfc.figure.u.59"></div>
     2194      <div id="rfc.figure.u.60"></div>
    21932195      <p>The following is an example response to the above hypothetical request:</p><pre class="text">HTTP/1.1 101 Switching Protocols
    21942196Connection: upgrade
    … …  
    22592261                  <td class="left">http</td>
    22602262                  <td class="left">standard</td>
    2261                   <td class="left"><a href="#header.trailer" id="rfc.xref.header.trailer.1" title="Trailer">Section&nbsp;4.1.1</a>
     2263                  <td class="left"><a href="#header.trailer" id="rfc.xref.header.trailer.1" title="Trailer">Section&nbsp;4.4</a>
    22622264                  </td>
    22632265               </tr>
    … …  
    30303032         indicating at least &lt;n&gt; and at most &lt;m&gt; elements, each separated by a single comma (",") and optional whitespace (OWS).
    30313033      </p>
    3032       <div id="rfc.figure.u.60"></div>
     3034      <div id="rfc.figure.u.61"></div>
    30333035      <p>Thus,</p><pre class="text">  1#element =&gt; element *( OWS "," OWS element )
    3034 </pre><div id="rfc.figure.u.61"></div>
     3036</pre><div id="rfc.figure.u.62"></div>
    30353037      <p>and:</p><pre class="text">  #element =&gt; [ 1#element ]
    3036 </pre><div id="rfc.figure.u.62"></div>
     3038</pre><div id="rfc.figure.u.63"></div>
    30373039      <p>and for n &gt;= 1 and m &gt; 1:</p><pre class="text">  &lt;n&gt;#&lt;m&gt;element =&gt; element &lt;n-1&gt;*&lt;m-1&gt;( OWS "," OWS element )
    30383040</pre><p id="rfc.section.B.p.6">For compatibility with legacy list rules, recipients <em class="bcp14">SHOULD</em> accept empty list elements. In other words, consumers would follow the list productions:
    30393041      </p>
    3040       <div id="rfc.figure.u.63"></div><pre class="text">  #element =&gt; [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
     3042      <div id="rfc.figure.u.64"></div><pre class="text">  #element =&gt; [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
    30413043 
    30423044  1#element =&gt; *( "," OWS ) element *( OWS "," [ OWS element ] )
    30433045</pre><p id="rfc.section.B.p.8">Note that empty elements do not contribute to the count of elements present, though.</p>
    30443046      <p id="rfc.section.B.p.9">For example, given these ABNF productions:</p>
    3045       <div id="rfc.figure.u.64"></div><pre class="text">  example-list      = 1#example-list-elmt
     3047      <div id="rfc.figure.u.65"></div><pre class="text">  example-list      = 1#example-list-elmt
    30463048  example-list-elmt = token ; see <a href="#field.components" title="Field value components">Section&nbsp;3.2.6</a>
    30473049</pre><p id="rfc.section.B.p.11">Then these are valid values for example-list (not including the double quotes, which are present for delimitation only):</p>
    3048       <div id="rfc.figure.u.65"></div><pre class="text">  "foo,bar"
     3050      <div id="rfc.figure.u.66"></div><pre class="text">  "foo,bar"
    30493051  "foo ,bar,"
    30503052  "foo , ,bar,charlie   "
    30513053</pre><p id="rfc.section.B.p.13">But these values would be invalid, as at least one non-empty element is required:</p>
    3052       <div id="rfc.figure.u.66"></div><pre class="text">  ""
     3054      <div id="rfc.figure.u.67"></div><pre class="text">  ""
    30533055  ","
    30543056  ",   ,"
    … …  
    30563058      </p>
    30573059      <h1 id="rfc.section.C"><a href="#rfc.section.C">C.</a>&nbsp;<a id="collected.abnf" href="#collected.abnf">Collected ABNF</a></h1>
    3058       <div id="rfc.figure.u.67"></div><pre class="inline"><a href="#rule.whitespace" class="smpl">BWS</a> = OWS
     3060      <div id="rfc.figure.u.68"></div><pre class="inline"><a href="#rule.whitespace" class="smpl">BWS</a> = OWS
    30593061
    30603062<a href="#header.connection" class="smpl">Connection</a> = *( "," OWS ) connection-option *( OWS "," [ OWS
    … …  
    31673169 "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
    31683170<a href="#rule.token.separators" class="smpl">token</a> = 1*tchar
    3169 <a href="#chunked.encoding" class="smpl">trailer-part</a> = *( header-field CRLF )
     3171<a href="#chunked.trailer.part" class="smpl">trailer-part</a> = *( header-field CRLF )
    31703172<a href="#transfer.codings" class="smpl">transfer-coding</a> = "chunked" / "compress" / "deflate" / "gzip" /
    31713173 transfer-extension
    … …  
    33153317                  <li><tt>Grammar</tt>&nbsp;&nbsp;
    33163318                     <ul>
    3317                         <li><tt>absolute-form</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.83"><b>5.3</b></a></li>
     3319                        <li><tt>absolute-form</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.84"><b>5.3</b></a></li>
    33183320                        <li><tt>absolute-path</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.19"><b>2.7</b></a></li>
    33193321                        <li><tt>absolute-URI</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.17"><b>2.7</b></a></li>
    33203322                        <li>ALPHA&nbsp;&nbsp;<a href="#rfc.iref.g.1"><b>1.2</b></a></li>
    3321                         <li><tt>asterisk-form</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.85"><b>5.3</b></a></li>
     3323                        <li><tt>asterisk-form</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.86"><b>5.3</b></a></li>
    33223324                        <li><tt>attribute</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.60"><b>4</b></a></li>
    33233325                        <li><tt>authority</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.18"><b>2.7</b></a></li>
    3324                         <li><tt>authority-form</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.84"><b>5.3</b></a></li>
     3326                        <li><tt>authority-form</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.85"><b>5.3</b></a></li>
    33253327                        <li><tt>BWS</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.42"><b>3.2.3</b></a></li>
    33263328                        <li><tt>chunk</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.65"><b>4.1</b></a></li>
    … …  
    33323334                        <li><tt>chunked-body</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.64"><b>4.1</b></a></li>
    33333335                        <li><tt>comment</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.51"><b>3.2.6</b></a></li>
    3334                         <li><tt>Connection</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.93"><b>6.1</b></a></li>
    3335                         <li><tt>connection-option</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.94"><b>6.1</b></a></li>
     3336                        <li><tt>Connection</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.94"><b>6.1</b></a></li>
     3337                        <li><tt>connection-option</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.95"><b>6.1</b></a></li>
    33363338                        <li><tt>Content-Length</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.56"><b>3.3.2</b></a></li>
    33373339                        <li>CR&nbsp;&nbsp;<a href="#rfc.iref.g.2"><b>1.2</b></a></li>
    … …  
    33493351                        <li><tt>header-field</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.35"><b>3.2</b></a></li>
    33503352                        <li>HEXDIG&nbsp;&nbsp;<a href="#rfc.iref.g.7"><b>1.2</b></a></li>
    3351                         <li><tt>Host</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.86"><b>5.4</b></a></li>
     3353                        <li><tt>Host</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.87"><b>5.4</b></a></li>
    33523354                        <li>HTAB&nbsp;&nbsp;<a href="#rfc.iref.g.8"><b>1.2</b></a></li>
    33533355                        <li><tt>HTTP-message</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.28"><b>3</b></a></li>
    … …  
    33633365                        <li><tt>obs-text</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.49"><b>3.2.6</b></a></li>
    33643366                        <li>OCTET&nbsp;&nbsp;<a href="#rfc.iref.g.10"><b>1.2</b></a></li>
    3365                         <li><tt>origin-form</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.82"><b>5.3</b></a></li>
     3367                        <li><tt>origin-form</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.83"><b>5.3</b></a></li>
    33663368                        <li><tt>OWS</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.40"><b>3.2.3</b></a></li>
    33673369                        <li><tt>partial-URI</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.25"><b>2.7</b></a></li>
    33683370                        <li><tt>port</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.20"><b>2.7</b></a></li>
    3369                         <li><tt>protocol-name</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.89"><b>5.7.1</b></a></li>
    3370                         <li><tt>protocol-version</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.90"><b>5.7.1</b></a></li>
    3371                         <li><tt>pseudonym</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.92"><b>5.7.1</b></a></li>
     3371                        <li><tt>protocol-name</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.90"><b>5.7.1</b></a></li>
     3372                        <li><tt>protocol-version</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.91"><b>5.7.1</b></a></li>
     3373                        <li><tt>pseudonym</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.93"><b>5.7.1</b></a></li>
    33723374                        <li><tt>qdtext</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.48"><b>3.2.6</b></a></li>
    33733375                        <li><tt>qdtext-nf</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.74"><b>4.1</b></a></li>
    … …  
    33793381                        <li><tt>rank</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.80"><b>4.3</b></a></li>
    33803382                        <li><tt>reason-phrase</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.34"><b>3.1.2</b></a></li>
    3381                         <li><tt>received-by</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.91"><b>5.7.1</b></a></li>
    3382                         <li><tt>received-protocol</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.88"><b>5.7.1</b></a></li>
     3383                        <li><tt>received-by</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.92"><b>5.7.1</b></a></li>
     3384                        <li><tt>received-protocol</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.89"><b>5.7.1</b></a></li>
    33833385                        <li><tt>request-line</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.30"><b>3.1.1</b></a></li>
    3384                         <li><tt>request-target</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.81"><b>5.3</b></a></li>
     3386                        <li><tt>request-target</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.82"><b>5.3</b></a></li>
    33853387                        <li><tt>RWS</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.41"><b>3.2.3</b></a></li>
    33863388                        <li><tt>segment</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.23"><b>2.7</b></a></li>
    … …  
    33953397                        <li><tt>TE</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.77"><b>4.3</b></a></li>
    33963398                        <li><tt>token</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.44"><b>3.2.6</b></a></li>
    3397                         <li><tt>Trailer</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.75"><b>4.1.1</b></a></li>
    3398                         <li><tt>trailer-part</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.72"><b>4.1</b></a></li>
     3399                        <li><tt>Trailer</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.81"><b>4.4</b></a></li>
     3400                        <li><tt>trailer-part</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.72">4.1</a>, <a href="#rfc.iref.g.75"><b>4.1.1</b></a></li>
    33993401                        <li><tt>transfer-coding</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.57"><b>4</b></a></li>
    34003402                        <li><tt>Transfer-Encoding</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.55"><b>3.3.1</b></a></li>
    34013403                        <li><tt>transfer-extension</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.58"><b>4</b></a></li>
    34023404                        <li><tt>transfer-parameter</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.59"><b>4</b></a></li>
    3403                         <li><tt>Upgrade</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.95"><b>6.7</b></a></li>
     3405                        <li><tt>Upgrade</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.96"><b>6.7</b></a></li>
    34043406                        <li><tt>uri-host</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.24"><b>2.7</b></a></li>
    34053407                        <li><tt>URI-reference</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.16"><b>2.7</b></a></li>
    34063408                        <li><tt>value</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.61"><b>4</b></a></li>
    34073409                        <li>VCHAR&nbsp;&nbsp;<a href="#rfc.iref.g.12"><b>1.2</b></a></li>
    3408                         <li><tt>Via</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.87"><b>5.7.1</b></a></li>
     3410                        <li><tt>Via</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.88"><b>5.7.1</b></a></li>
    34093411                        <li><tt>word</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.43"><b>3.2.6</b></a></li>
    34103412                     </ul>
    … …  
    35753577                  <li>target resource&nbsp;&nbsp;<a href="#rfc.iref.t.7"><b>5.1</b></a></li>
    35763578                  <li>target URI&nbsp;&nbsp;<a href="#rfc.iref.t.8"><b>5.1</b></a></li>
    3577                   <li>TE header field&nbsp;&nbsp;<a href="#rfc.xref.header.te.1">4</a>, <a href="#rfc.xref.header.te.2">4.1.1</a>, <a href="#rfc.iref.t.6"><b>4.3</b></a>, <a href="#rfc.xref.header.te.3">7.1</a></li>
    3578                   <li>Trailer header field&nbsp;&nbsp;<a href="#rfc.iref.t.5"><b>4.1.1</b></a>, <a href="#rfc.xref.header.trailer.1">7.1</a></li>
     3579                  <li>TE header field&nbsp;&nbsp;<a href="#rfc.xref.header.te.1">4</a>, <a href="#rfc.xref.header.te.2">4.1.1</a>, <a href="#rfc.iref.t.5"><b>4.3</b></a>, <a href="#rfc.xref.header.te.3">7.1</a></li>
     3580                  <li>Trailer header field&nbsp;&nbsp;<a href="#rfc.iref.t.6"><b>4.4</b></a>, <a href="#rfc.xref.header.trailer.1">7.1</a></li>
    35793581                  <li>Transfer-Encoding header field&nbsp;&nbsp;<a href="#rfc.xref.header.transfer-encoding.1">3.3</a>, <a href="#rfc.iref.t.4"><b>3.3.1</b></a>, <a href="#rfc.xref.header.transfer-encoding.2">4</a>, <a href="#rfc.xref.header.transfer-encoding.3">7.1</a>, <a href="#rfc.xref.header.transfer-encoding.4">A.1.3</a></li>
    35803582                  <li>transforming proxy&nbsp;&nbsp;<a href="#rfc.iref.t.1"><b>2.3</b></a></li>

  • draft-ietf-httpbis/latest/p1-messaging.xml

    r2338 r2339  
    19761976  <x:anchor-alias value="chunk-size"/>
    19771977  <x:anchor-alias value="last-chunk"/>
    1978   <x:anchor-alias value="trailer-part"/>
    19791978  <x:anchor-alias value="quoted-str-nf"/>
    19801979  <x:anchor-alias value="qdtext-nf"/>
    … …  
    19871986   received the full message.
    19881987</t>
    1989 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="chunked-body"><!--terminal production--></iref><iref primary="true" item="Grammar" subitem="chunk"/><iref primary="true" item="Grammar" subitem="chunk-size"/><iref primary="true" item="Grammar" subitem="last-chunk"/><iref primary="true" item="Grammar" subitem="chunk-ext"/><iref primary="true" item="Grammar" subitem="chunk-ext-name"/><iref primary="true" item="Grammar" subitem="chunk-ext-val"/><iref primary="true" item="Grammar" subitem="chunk-data"/><iref primary="true" item="Grammar" subitem="trailer-part"/><iref primary="true" item="Grammar" subitem="quoted-str-nf"/><iref primary="true" item="Grammar" subitem="qdtext-nf"/>
     1988<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="chunked-body"><!--terminal production--></iref><iref primary="true" item="Grammar" subitem="chunk"/><iref primary="true" item="Grammar" subitem="chunk-size"/><iref primary="true" item="Grammar" subitem="last-chunk"/><iref primary="true" item="Grammar" subitem="chunk-ext"/><iref primary="true" item="Grammar" subitem="chunk-ext-name"/><iref primary="true" item="Grammar" subitem="chunk-ext-val"/><iref primary="true" item="Grammar" subitem="chunk-data"/><iref primary="false" item="Grammar" subitem="trailer-part"/><iref primary="true" item="Grammar" subitem="quoted-str-nf"/><iref primary="true" item="Grammar" subitem="qdtext-nf"/>
    19901989  <x:ref>chunked-body</x:ref>   = *<x:ref>chunk</x:ref>
    19911990                   <x:ref>last-chunk</x:ref>
    … …  
    20022001  <x:ref>chunk-ext-val</x:ref>  = <x:ref>token</x:ref> / <x:ref>quoted-str-nf</x:ref>
    20032002  <x:ref>chunk-data</x:ref>     = 1*<x:ref>OCTET</x:ref> ; a sequence of chunk-size octets
    2004   <x:ref>trailer-part</x:ref>   = *( <x:ref>header-field</x:ref> <x:ref>CRLF</x:ref> )
    20052003 
    20062004  <x:ref>quoted-str-nf</x:ref>  = <x:ref>DQUOTE</x:ref> *( <x:ref>qdtext-nf</x:ref> / <x:ref>quoted-pair</x:ref> ) <x:ref>DQUOTE</x:ref>
    … …  
    20202018</t>
    20212019
    2022 <section title="Trailer" anchor="header.trailer">
    2023   <iref primary="true" item="Trailer header field" x:for-anchor=""/>
    2024   <x:anchor-alias value="Trailer"/>
     2020<section title="Chunked Trailer Part" anchor="chunked.trailer.part">
     2021  <x:anchor-alias value="trailer-part"/>
    20252022<t>
    20262023   A trailer allows the sender to include additional fields at the end of a
    … …  
    20312028   instead of the message header block.
    20322029</t>
    2033 <t>
    2034    When a message includes a message body encoded with the chunked
    2035    transfer coding and the sender desires to send metadata in the form of
    2036    trailer fields at the end of the message, the sender &SHOULD; generate a
    2037    <x:ref>Trailer</x:ref> header field before the message body to indicate
    2038    which fields will be present in the trailers. This allows the recipient
    2039    to prepare for receipt of that metadata before it starts processing the body,
    2040    which is useful if the message is being streamed and the recipient wishes
    2041    to confirm an integrity check on the fly.
    2042 </t>
    2043 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Trailer"/>
    2044   <x:ref>Trailer</x:ref> = 1#<x:ref>field-name</x:ref>
     2030<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="trailer-part"/>
     2031  <x:ref>trailer-part</x:ref>   = *( <x:ref>header-field</x:ref> <x:ref>CRLF</x:ref> )
    20452032</artwork></figure>
    20462033<t>
    … …  
    20802067</section>
    20812068
    2082 <section title="Decoding chunked" anchor="decoding.chunked">
     2069<section title="Decoding Chunked" anchor="decoding.chunked">
    20832070<t>
    20842071   A process for decoding the chunked transfer coding
    … …  
    21912178   The presence of the keyword "trailers" indicates that the client is willing
    21922179   to accept trailer fields in a chunked transfer coding, as defined in
    2193    <xref target="chunked.encoding"/>, on behalf of itself and any downstream
     2180   <xref target="chunked.trailer.part"/>, on behalf of itself and any downstream
    21942181   clients. For requests from an intermediary, this implies that either:
    21952182   (a) all downstream clients are willing to accept trailer fields in the
    … …  
    22202207   that do not support its semantics.
    22212208</t>
     2209</section>
     2210
     2211<section title="Trailer" anchor="header.trailer">
     2212  <iref primary="true" item="Trailer header field" x:for-anchor=""/>
     2213  <x:anchor-alias value="Trailer"/>
     2214<t>
     2215   When a message includes a message body encoded with the chunked
     2216   transfer coding and the sender desires to send metadata in the form of
     2217   trailer fields at the end of the message, the sender &SHOULD; generate a
     2218   <x:ref>Trailer</x:ref> header field before the message body to indicate
     2219   which fields will be present in the trailers. This allows the recipient
     2220   to prepare for receipt of that metadata before it starts processing the body,
     2221   which is useful if the message is being streamed and the recipient wishes
     2222   to confirm an integrity check on the fly.
     2223</t>
     2224<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Trailer"/>
     2225  <x:ref>Trailer</x:ref> = 1#<x:ref>field-name</x:ref>
     2226</artwork></figure>
    22222227</section>
    22232228</section>
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