14/12/11 03:21:58 (10 years ago)

Clarify Proxy-Connection; #158

1 edited


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

    r1491 r1492  
    48994899<section title="Keep-Alive Connections" anchor="compatibility.with.http.1.0.persistent.connections">
    4901    For most implementations of HTTP/1.0, each connection is established
    4902    by the client prior to the request and closed by the server after
    4903    sending the response. However, some implementations implement the
    4904    Keep-Alive version of persistent connections described in
    4905    <xref x:sec="19.7.1" x:fmt="of" target="RFC2068"/>.
    4906 </t>
    4907 <t>
    4908    Some clients and servers might wish to be compatible with some
    4909    previous implementations of persistent connections in HTTP/1.0
    4910    clients and servers. Persistent connections in HTTP/1.0 are
    4911    explicitly negotiated as they are not the default behavior. HTTP/1.0
    4912    experimental implementations of persistent connections are faulty,
    4913    and the new facilities in HTTP/1.1 are designed to rectify these
    4914    problems. The problem was that some existing HTTP/1.0 clients might
    4915    send Keep-Alive to a proxy server that doesn't understand
    4916    Connection, which would then erroneously forward it to the next
    4917    inbound server, which would establish the Keep-Alive connection and
    4918    result in a hung HTTP/1.0 proxy waiting for the close on the
    4919    response. The result is that HTTP/1.0 clients must be prevented from
    4920    using Keep-Alive when talking to proxies.
    4921 </t>
    4922 <t>
    4923    However, talking to proxies is the most important use of persistent
    4924    connections, so that prohibition is clearly unacceptable. Therefore,
    4925    we need some other mechanism for indicating a persistent connection
    4926    is desired, which is safe to use even when talking to an old proxy
    4927    that ignores Connection. Persistent connections are the default for
    4928    HTTP/1.1 messages; we introduce a new keyword (Connection: close) for
    4929    declaring non-persistence. See <xref target="header.connection"/>.
     4901   In HTTP/1.0, each connection is established by the client prior to the
     4902   request and closed by the server after sending the response. However, some
     4903   implementations implement the explicitly negotiated ("Keep-Alive") version
     4904   of persistent connections described in <xref x:sec="19.7.1" x:fmt="of"
     4905   target="RFC2068"/>.
     4908   Some clients and servers might wish to be compatible with these previous
     4909   approaches to persistent connections, by explicitly negotiating for them
     4910   with a "Connection: keep-alive" request header field. However, some
     4911   experimental implementations of HTTP/1.0 persistent connections are faulty;
     4912   for example, if a HTTP/1.0 proxy server doesn't understand Connection, it
     4913   will erroneously forward that header to the next inbound server, which
     4914   would result in a hung connection.
     4917   One attempted solution was the introduction of a Proxy-Connection header,
     4918   targeted specifically at proxies. In practice, this was also unworkable,
     4919   because proxies are often deployed in multiple layers, bringing about the
     4920   same problem discussed above.
     4923   As a result, clients are encouraged not to send the Proxy-Connection header
     4924   in any requests.
     4927   Clients are also encouraged to consider the use of Connection: keep-alive
     4928   in requests carefully; while they can enable persistent connections with
     4929   HTTP/1.0 servers, clients using them need will need to monitor the
     4930   connection for "hung" requests (which indicate that the client ought stop
     4931   sending the header), and this mechanism ought not be used by clients at all
     4932   when a proxy is being used.
    58925895      "Intermediary rewriting of queries"
    58935896    </t>
     5897    <t>
     5898      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/158"/>:
     5899      "Proxy-Connection and Keep-Alive"
     5900    </t>
    58945901  </list>
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