Changeset 386 for draft-ietf-httpbis/latest/p2-semantics.html
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- 14/11/08 21:14:27 (14 years ago)
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draft-ietf-httpbis/latest/p2-semantics.html
r382 r386 675 675 <p id="rfc.section.2.p.1">This specification uses the ABNF syntax defined in <a href="p1-messaging.html#notation.abnf" title="ABNF Extension: #rule">Section 2.1</a> of <a href="#Part1" id="rfc.xref.Part1.2"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> and the core rules defined in <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a> of <a href="#Part1" id="rfc.xref.Part1.3"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>: 676 676 </p> 677 <div id="rfc.figure.u.1"></div><pre class="inline"> <a href="#notation" class="smpl">DIGIT</a> = <DIGIT, defined in <a href="#Part1" id="rfc.xref.Part1.4"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 678 </pre><div id="rfc.figure.u.2"></div><pre class="inline"> <a href="#notation" class="smpl">comment</a> = <comment, defined in <a href="#Part1" id="rfc.xref.Part1.5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 679 <a href="#notation" class="smpl">quoted-string</a> = <quoted-string, defined in <a href="#Part1" id="rfc.xref.Part1.6"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 680 <a href="#notation" class="smpl">token</a> = <token, defined in <a href="#Part1" id="rfc.xref.Part1.7"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 681 <a href="#notation" class="smpl">OWS</a> = <OWS, defined in <a href="#Part1" id="rfc.xref.Part1.8"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 682 <a href="#notation" class="smpl">RWS</a> = <RWS, defined in <a href="#Part1" id="rfc.xref.Part1.9"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 677 <div id="rfc.figure.u.1"></div><pre class="inline"> <a href="#notation" class="smpl">CR</a> = <CR, defined in <a href="#Part1" id="rfc.xref.Part1.4"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 678 <a href="#notation" class="smpl">DIGIT</a> = <DIGIT, defined in <a href="#Part1" id="rfc.xref.Part1.5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 679 <a href="#notation" class="smpl">LF</a> = <LF, defined in <a href="#Part1" id="rfc.xref.Part1.6"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 680 </pre><div id="rfc.figure.u.2"></div><pre class="inline"> <a href="#notation" class="smpl">comment</a> = <comment, defined in <a href="#Part1" id="rfc.xref.Part1.7"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 681 <a href="#notation" class="smpl">quoted-string</a> = <quoted-string, defined in <a href="#Part1" id="rfc.xref.Part1.8"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 682 <a href="#notation" class="smpl">token</a> = <token, defined in <a href="#Part1" id="rfc.xref.Part1.9"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 683 <a href="#notation" class="smpl">OWS</a> = <OWS, defined in <a href="#Part1" id="rfc.xref.Part1.10"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 684 <a href="#notation" class="smpl">RWS</a> = <RWS, defined in <a href="#Part1" id="rfc.xref.Part1.11"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 685 <a href="#notation" class="smpl">TEXT</a> = <TEXT, defined in <a href="#Part1" id="rfc.xref.Part1.12"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>> 683 686 </pre><div id="abnf.dependencies"> 684 687 <p id="rfc.section.2.p.4"> The ABNF rules below are defined in other parts:</p> 685 688 </div> 686 <div id="rfc.figure.u.3"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">absolute-URI</a> = <absolute-URI, defined in <a href="#Part1" id="rfc.xref.Part1.1 0"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 3.2</a>>687 <a href="#abnf.dependencies" class="smpl">fragment</a> = <fragment, defined in <a href="#Part1" id="rfc.xref.Part1.1 1"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 3.2</a>>688 <a href="#abnf.dependencies" class="smpl">Host</a> = <Host, defined in <a href="#Part1" id="rfc.xref.Part1.1 2"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 3.2</a>>689 <a href="#abnf.dependencies" class="smpl">HTTP-date</a> = <HTTP-date, defined in <a href="#Part1" id="rfc.xref.Part1.1 3"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#full.date" title="Full Date">Section 3.3.1</a>>690 <a href="#abnf.dependencies" class="smpl">product</a> = <product, defined in <a href="#Part1" id="rfc.xref.Part1.1 4"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</a>>691 <a href="#abnf.dependencies" class="smpl">relativeURI</a> = <relativeURI, defined in <a href="#Part1" id="rfc.xref.Part1.1 5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 3.2</a>>692 <a href="#abnf.dependencies" class="smpl">TE</a> = <TE, defined in <a href="#Part1" id="rfc.xref.Part1.1 6"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 8.8</a>>689 <div id="rfc.figure.u.3"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">absolute-URI</a> = <absolute-URI, defined in <a href="#Part1" id="rfc.xref.Part1.13"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 3.2</a>> 690 <a href="#abnf.dependencies" class="smpl">fragment</a> = <fragment, defined in <a href="#Part1" id="rfc.xref.Part1.14"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 3.2</a>> 691 <a href="#abnf.dependencies" class="smpl">Host</a> = <Host, defined in <a href="#Part1" id="rfc.xref.Part1.15"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 3.2</a>> 692 <a href="#abnf.dependencies" class="smpl">HTTP-date</a> = <HTTP-date, defined in <a href="#Part1" id="rfc.xref.Part1.16"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#full.date" title="Full Date">Section 3.3.1</a>> 693 <a href="#abnf.dependencies" class="smpl">product</a> = <product, defined in <a href="#Part1" id="rfc.xref.Part1.17"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</a>> 694 <a href="#abnf.dependencies" class="smpl">relativeURI</a> = <relativeURI, defined in <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 3.2</a>> 695 <a href="#abnf.dependencies" class="smpl">TE</a> = <TE, defined in <a href="#Part1" id="rfc.xref.Part1.19"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 8.8</a>> 693 696 </pre><div id="rfc.figure.u.4"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">Accept</a> = <Accept, defined in <a href="#Part3" id="rfc.xref.Part3.1"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept" title="Accept">Section 6.1</a>> 694 697 <a href="#abnf.dependencies" class="smpl">Accept-Charset</a> = … … 762 765 / <a href="#header.expect" class="smpl">Expect</a> ; <a href="#header.expect" id="rfc.xref.header.expect.1" title="Expect">Section 10.2</a> 763 766 / <a href="#header.from" class="smpl">From</a> ; <a href="#header.from" id="rfc.xref.header.from.1" title="From">Section 10.3</a> 764 / <a href="#abnf.dependencies" class="smpl">Host</a> ; <a href="#Part1" id="rfc.xref.Part1. 17"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.host" title="Host">Section 8.4</a>767 / <a href="#abnf.dependencies" class="smpl">Host</a> ; <a href="#Part1" id="rfc.xref.Part1.20"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.host" title="Host">Section 8.4</a> 765 768 / <a href="#abnf.dependencies" class="smpl">If-Match</a> ; <a href="#Part4" id="rfc.xref.Part4.6"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-match" title="If-Match">Section 7.2</a> 766 769 / <a href="#abnf.dependencies" class="smpl">If-Modified-Since</a> ; <a href="#Part4" id="rfc.xref.Part4.7"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-modified-since" title="If-Modified-Since">Section 7.3</a> … … 772 775 / <a href="#abnf.dependencies" class="smpl">Range</a> ; <a href="#Part5" id="rfc.xref.Part5.5"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.range" title="Range">Section 6.4</a> 773 776 / <a href="#header.referer" class="smpl">Referer</a> ; <a href="#header.referer" id="rfc.xref.header.referer.1" title="Referer">Section 10.6</a> 774 / <a href="#abnf.dependencies" class="smpl">TE</a> ; <a href="#Part1" id="rfc.xref.Part1. 18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 8.8</a>777 / <a href="#abnf.dependencies" class="smpl">TE</a> ; <a href="#Part1" id="rfc.xref.Part1.21"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 8.8</a> 775 778 / <a href="#header.user-agent" class="smpl">User-Agent</a> ; <a href="#header.user-agent" id="rfc.xref.header.user-agent.1" title="User-Agent">Section 10.9</a> 776 779 </pre><p id="rfc.section.4.p.3">Request-header field names can be extended reliably only in combination with a change in the protocol version. However, new … … 830 833 831 834 <a href="#request.header.fields" class="smpl">extension-code</a> = 3<a href="#notation" class="smpl">DIGIT</a> 832 <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a> = *< TEXT, excluding CR, LF>835 <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a> = *<<a href="#notation" class="smpl">TEXT</a>, excluding <a href="#notation" class="smpl">CR</a>, <a href="#notation" class="smpl">LF</a>> 833 836 </pre><p id="rfc.section.5.p.4">HTTP status codes are extensible. HTTP applications are not required to understand the meaning of all registered status codes, 834 837 though such understanding is obviously desirable. However, applications <em class="bcp14">MUST</em> understand the class of any status code, as indicated by the first digit, and treat any unrecognized response as being equivalent … … 868 871 fields are defined in <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. 869 872 </p> 870 <p id="rfc.section.7.p.2">An entity-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 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>. The entity-body is obtained from the message-body by decoding any Transfer-Encoding that might have been applied to ensure873 <p id="rfc.section.7.p.2">An entity-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 4.3</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>. The entity-body is obtained from the message-body by decoding any Transfer-Encoding that might have been applied to ensure 871 874 safe and proper transfer of the message. 872 875 </p> … … 1033 1036 </p> 1034 1037 <p id="rfc.section.8.8.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 1035 or diagnostic information. The value of the Via header field (<a href="p1-messaging.html#header.via" title="Via">Section 8.9</a> of <a href="#Part1" id="rfc.xref.Part1.2 0"><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 the1038 or diagnostic information. The value of the Via header field (<a href="p1-messaging.html#header.via" title="Via">Section 8.9</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>) is of particular interest, since it acts as a trace of the request chain. Use of the Max-Forwards header field allows the 1036 1039 client to limit the length of the request chain, which is useful for testing a chain of proxies forwarding messages in an 1037 1040 infinite loop. 1038 1041 </p> 1039 <p id="rfc.section.8.8.p.3">If the request is valid, the response <em class="bcp14">SHOULD</em> contain the entire request message in the entity-body, with a Content-Type of "message/http" (see <a href="p1-messaging.html#internet.media.type.message.http" title="Internet Media Type message/http">Section 9.3.1</a> of <a href="#Part1" id="rfc.xref.Part1.2 1"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). Responses to this method <em class="bcp14">MUST NOT</em> be cached.1042 <p id="rfc.section.8.8.p.3">If the request is valid, the response <em class="bcp14">SHOULD</em> contain the entire request message in the entity-body, with a Content-Type of "message/http" (see <a href="p1-messaging.html#internet.media.type.message.http" title="Internet Media Type message/http">Section 9.3.1</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>). Responses to this method <em class="bcp14">MUST NOT</em> be cached. 1040 1043 </p> 1041 1044 <div id="rfc.iref.c.1"></div> … … 1066 1069 <p id="rfc.section.9.1.1.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 1067 1070 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 1068 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.Part1.2 2"><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.1071 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. 1069 1072 </p> 1070 1073 <div id="rfc.iref.26"></div> … … 1449 1452 <p id="rfc.section.9.5.6.p.1">The server does not support, or refuses to support, the protocol version that was used in the request message. The server 1450 1453 is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described 1451 in <a href="p1-messaging.html#http.version" title="HTTP Version">Section 3.1</a> of <a href="#Part1" id="rfc.xref.Part1.2 3"><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 an entity describing why that version is not supported and what other protocols are supported by that server.1454 in <a href="p1-messaging.html#http.version" title="HTTP Version">Section 3.1</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>, other than with this error message. The response <em class="bcp14">SHOULD</em> contain an entity describing why that version is not supported and what other protocols are supported by that server. 1452 1455 </p> 1453 1456 <h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a> <a id="header.fields" href="#header.fields">Header Field Definitions</a></h1> … … 1495 1498 </p> 1496 1499 <p id="rfc.section.10.2.p.7">Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header.</p> 1497 <p id="rfc.section.10.2.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.Part1.2 4"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for the use of the 100 (Continue) status.1500 <p id="rfc.section.10.2.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.Part1.27"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for the use of the 100 (Continue) status. 1498 1501 </p> 1499 1502 <div id="rfc.iref.f.1"></div> … … 1595 1598 <h2 id="rfc.section.10.8"><a href="#rfc.section.10.8">10.8</a> <a id="header.server" href="#header.server">Server</a></h2> 1596 1599 <p id="rfc.section.10.8.p.1">The response-header field "Server" contains information about the software used by the origin server to handle the request. 1597 The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</a> of <a href="#Part1" id="rfc.xref.Part1.2 5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments identifying the server and any significant subproducts. The product tokens are listed in order of their significance1600 The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</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>) and comments identifying the server and any significant subproducts. The product tokens are listed in order of their significance 1598 1601 for identifying the application. 1599 1602 </p> … … 1603 1606 </pre><p id="rfc.section.10.8.p.3">Example:</p> 1604 1607 <div id="rfc.figure.u.27"></div><pre class="text"> Server: CERN/3.0 libwww/2.17 1605 </pre><p id="rfc.section.10.8.p.5">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server response-header. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 8.9</a> of <a href="#Part1" id="rfc.xref.Part1.2 6"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).1608 </pre><p id="rfc.section.10.8.p.5">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server response-header. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 8.9</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>). 1606 1609 </p> 1607 1610 <dl class="empty"> … … 1616 1619 <p id="rfc.section.10.9.p.1">The request-header field "User-Agent" contains information about the user agent originating the request. This is for statistical 1617 1620 purposes, the tracing of protocol violations, and automated recognition of user agents for the sake of tailoring responses 1618 to avoid particular user agent limitations. User agents <em class="bcp14">SHOULD</em> include this field with requests. The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</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>) and comments identifying the agent and any subproducts which form a significant part of the user agent. By convention, the1621 to avoid particular user agent limitations. User agents <em class="bcp14">SHOULD</em> include this field with requests. The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</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>) and comments identifying the agent and any subproducts which form a significant part of the user agent. By convention, the 1619 1622 product tokens are listed in order of their significance for identifying the application. 1620 1623 </p> … … 2230 2233 </p> 2231 2234 <p id="rfc.section.A.2.p.7">In the description of the Server header, the Via field was described as a SHOULD. The requirement was and is stated correctly 2232 in the description of the Via header in <a href="p1-messaging.html#header.via" title="Via">Section 8.9</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>. (<a href="#header.server" id="rfc.xref.header.server.4" title="Server">Section 10.8</a>)2235 in the description of the Via header in <a href="p1-messaging.html#header.via" title="Via">Section 8.9</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>. (<a href="#header.server" id="rfc.xref.header.server.4" title="Server">Section 10.8</a>) 2233 2236 </p> 2234 2237 <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a> <a id="change.log" href="#change.log">Change Log (to be removed by RFC Editor before publication)</a></h1> … … 2530 2533 </li> 2531 2534 <li class="indline0"><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul class="ind"> 2532 <li class="indline1"><em>Part1</em> <a class="iref" href="#rfc.xref.Part1.1">1</a>, <a class="iref" href="#rfc.xref.Part1.2">2</a>, <a class="iref" href="#rfc.xref.Part1.3">2</a>, <a class="iref" href="#rfc.xref.Part1.4">2</a>, <a class="iref" href="#rfc.xref.Part1.5">2</a>, <a class="iref" href="#rfc.xref.Part1.6">2</a>, <a class="iref" href="#rfc.xref.Part1.7">2</a>, <a class="iref" href="#rfc.xref.Part1.8">2</a>, <a class="iref" href="#rfc.xref.Part1.9">2</a>, <a class="iref" href="#rfc.xref.Part1.10">2</a>, <a class="iref" href="#rfc.xref.Part1.11">2</a>, <a class="iref" href="#rfc.xref.Part1.12">2</a>, <a class="iref" href="#rfc.xref.Part1.13">2</a>, <a class="iref" href="#rfc.xref.Part1.14">2</a>, <a class="iref" href="#rfc.xref.Part1.15">2</a>, <a class="iref" href="#rfc.xref.Part1.16">2</a>, <a class="iref" href="#rfc.xref.Part1.17"> 4</a>, <a class="iref" href="#rfc.xref.Part1.18">4</a>, <a class="iref" href="#rfc.xref.Part1.19">7</a>, <a class="iref" href="#rfc.xref.Part1.20">8.8</a>, <a class="iref" href="#rfc.xref.Part1.21">8.8</a>, <a class="iref" href="#rfc.xref.Part1.22">9.1.1</a>, <a class="iref" href="#rfc.xref.Part1.23">9.5.6</a>, <a class="iref" href="#rfc.xref.Part1.24">10.2</a>, <a class="iref" href="#rfc.xref.Part1.25">10.8</a>, <a class="iref" href="#rfc.xref.Part1.26">10.8</a>, <a class="iref" href="#rfc.xref.Part1.27">10.9</a>, <a class="iref" href="#Part1"><b>14.1</b></a>, <a class="iref" href="#rfc.xref.Part1.28">A.2</a><ul class="ind">2535 <li class="indline1"><em>Part1</em> <a class="iref" href="#rfc.xref.Part1.1">1</a>, <a class="iref" href="#rfc.xref.Part1.2">2</a>, <a class="iref" href="#rfc.xref.Part1.3">2</a>, <a class="iref" href="#rfc.xref.Part1.4">2</a>, <a class="iref" href="#rfc.xref.Part1.5">2</a>, <a class="iref" href="#rfc.xref.Part1.6">2</a>, <a class="iref" href="#rfc.xref.Part1.7">2</a>, <a class="iref" href="#rfc.xref.Part1.8">2</a>, <a class="iref" href="#rfc.xref.Part1.9">2</a>, <a class="iref" href="#rfc.xref.Part1.10">2</a>, <a class="iref" href="#rfc.xref.Part1.11">2</a>, <a class="iref" href="#rfc.xref.Part1.12">2</a>, <a class="iref" href="#rfc.xref.Part1.13">2</a>, <a class="iref" href="#rfc.xref.Part1.14">2</a>, <a class="iref" href="#rfc.xref.Part1.15">2</a>, <a class="iref" href="#rfc.xref.Part1.16">2</a>, <a class="iref" href="#rfc.xref.Part1.17">2</a>, <a class="iref" href="#rfc.xref.Part1.18">2</a>, <a class="iref" href="#rfc.xref.Part1.19">2</a>, <a class="iref" href="#rfc.xref.Part1.20">4</a>, <a class="iref" href="#rfc.xref.Part1.21">4</a>, <a class="iref" href="#rfc.xref.Part1.22">7</a>, <a class="iref" href="#rfc.xref.Part1.23">8.8</a>, <a class="iref" href="#rfc.xref.Part1.24">8.8</a>, <a class="iref" href="#rfc.xref.Part1.25">9.1.1</a>, <a class="iref" href="#rfc.xref.Part1.26">9.5.6</a>, <a class="iref" href="#rfc.xref.Part1.27">10.2</a>, <a class="iref" href="#rfc.xref.Part1.28">10.8</a>, <a class="iref" href="#rfc.xref.Part1.29">10.8</a>, <a class="iref" href="#rfc.xref.Part1.30">10.9</a>, <a class="iref" href="#Part1"><b>14.1</b></a>, <a class="iref" href="#rfc.xref.Part1.31">A.2</a><ul class="ind"> 2533 2536 <li class="indline1"><em>Section 2.1</em> <a class="iref" href="#rfc.xref.Part1.2">2</a></li> 2534 <li class="indline1"><em>Section 2.2</em> <a class="iref" href="#rfc.xref.Part1.3">2</a>, <a class="iref" href="#rfc.xref.Part1.4">2</a>, <a class="iref" href="#rfc.xref.Part1.5">2</a>, <a class="iref" href="#rfc.xref.Part1.6">2</a>, <a class="iref" href="#rfc.xref.Part1.7">2</a>, <a class="iref" href="#rfc.xref.Part1.8">2</a>, <a class="iref" href="#rfc.xref.Part1.9">2</a> </li>2535 <li class="indline1"><em>Section 3.1</em> <a class="iref" href="#rfc.xref.Part1.2 3">9.5.6</a></li>2536 <li class="indline1"><em>Section 3.2</em> <a class="iref" href="#rfc.xref.Part1.1 0">2</a>, <a class="iref" href="#rfc.xref.Part1.11">2</a>, <a class="iref" href="#rfc.xref.Part1.12">2</a>, <a class="iref" href="#rfc.xref.Part1.15">2</a></li>2537 <li class="indline1"><em>Section 3.3.1</em> <a class="iref" href="#rfc.xref.Part1.1 3">2</a></li>2538 <li class="indline1"><em>Section 3.5</em> <a class="iref" href="#rfc.xref.Part1.1 4">2</a>, <a class="iref" href="#rfc.xref.Part1.25">10.8</a>, <a class="iref" href="#rfc.xref.Part1.27">10.9</a></li>2539 <li class="indline1"><em>Section 4.3</em> <a class="iref" href="#rfc.xref.Part1. 19">7</a></li>2540 <li class="indline1"><em>Section 7.2.3</em> <a class="iref" href="#rfc.xref.Part1.2 2">9.1.1</a>, <a class="iref" href="#rfc.xref.Part1.24">10.2</a></li>2541 <li class="indline1"><em>Section 8.4</em> <a class="iref" href="#rfc.xref.Part1. 17">4</a></li>2542 <li class="indline1"><em>Section 8.8</em> <a class="iref" href="#rfc.xref.Part1.1 6">2</a>, <a class="iref" href="#rfc.xref.Part1.18">4</a></li>2543 <li class="indline1"><em>Section 8.9</em> <a class="iref" href="#rfc.xref.Part1.2 0">8.8</a>, <a class="iref" href="#rfc.xref.Part1.26">10.8</a>, <a class="iref" href="#rfc.xref.Part1.28">A.2</a></li>2544 <li class="indline1"><em>Section 9.3.1</em> <a class="iref" href="#rfc.xref.Part1.2 1">8.8</a></li>2537 <li class="indline1"><em>Section 2.2</em> <a class="iref" href="#rfc.xref.Part1.3">2</a>, <a class="iref" href="#rfc.xref.Part1.4">2</a>, <a class="iref" href="#rfc.xref.Part1.5">2</a>, <a class="iref" href="#rfc.xref.Part1.6">2</a>, <a class="iref" href="#rfc.xref.Part1.7">2</a>, <a class="iref" href="#rfc.xref.Part1.8">2</a>, <a class="iref" href="#rfc.xref.Part1.9">2</a>, <a class="iref" href="#rfc.xref.Part1.10">2</a>, <a class="iref" href="#rfc.xref.Part1.11">2</a>, <a class="iref" href="#rfc.xref.Part1.12">2</a></li> 2538 <li class="indline1"><em>Section 3.1</em> <a class="iref" href="#rfc.xref.Part1.26">9.5.6</a></li> 2539 <li class="indline1"><em>Section 3.2</em> <a class="iref" href="#rfc.xref.Part1.13">2</a>, <a class="iref" href="#rfc.xref.Part1.14">2</a>, <a class="iref" href="#rfc.xref.Part1.15">2</a>, <a class="iref" href="#rfc.xref.Part1.18">2</a></li> 2540 <li class="indline1"><em>Section 3.3.1</em> <a class="iref" href="#rfc.xref.Part1.16">2</a></li> 2541 <li class="indline1"><em>Section 3.5</em> <a class="iref" href="#rfc.xref.Part1.17">2</a>, <a class="iref" href="#rfc.xref.Part1.28">10.8</a>, <a class="iref" href="#rfc.xref.Part1.30">10.9</a></li> 2542 <li class="indline1"><em>Section 4.3</em> <a class="iref" href="#rfc.xref.Part1.22">7</a></li> 2543 <li class="indline1"><em>Section 7.2.3</em> <a class="iref" href="#rfc.xref.Part1.25">9.1.1</a>, <a class="iref" href="#rfc.xref.Part1.27">10.2</a></li> 2544 <li class="indline1"><em>Section 8.4</em> <a class="iref" href="#rfc.xref.Part1.20">4</a></li> 2545 <li class="indline1"><em>Section 8.8</em> <a class="iref" href="#rfc.xref.Part1.19">2</a>, <a class="iref" href="#rfc.xref.Part1.21">4</a></li> 2546 <li class="indline1"><em>Section 8.9</em> <a class="iref" href="#rfc.xref.Part1.23">8.8</a>, <a class="iref" href="#rfc.xref.Part1.29">10.8</a>, <a class="iref" href="#rfc.xref.Part1.31">A.2</a></li> 2547 <li class="indline1"><em>Section 9.3.1</em> <a class="iref" href="#rfc.xref.Part1.24">8.8</a></li> 2545 2548 </ul> 2546 2549 </li>
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