Changeset 1492 for draft-ietf-httpbis/latest/p1-messaging.xml

Timestamp:

Dec 13, 2011, 7:21:58 PM (8 years ago)

Author:

mnot@…

Message:

Clarify Proxy-Connection; #158

File:

• draft-ietf-httpbis/latest/p1-messaging.xml (modified) (2 diffs)

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

@@ -4899 +4899 @@
 <section title="Keep-Alive Connections" anchor="compatibility.with.http.1.0.persistent.connections">
 <t>
-   For most implementations of HTTP/1.0, each connection is established
-   by the client prior to the request and closed by the server after
-   sending the response. However, some implementations implement the
-   Keep-Alive version of persistent connections described in
-   <xref x:sec="19.7.1" x:fmt="of" target="RFC2068"/>.
-</t>
-<t>
-   Some clients and servers might wish to be compatible with some
-   previous implementations of persistent connections in HTTP/1.0
-   clients and servers. Persistent connections in HTTP/1.0 are
-   explicitly negotiated as they are not the default behavior. HTTP/1.0
-   experimental implementations of persistent connections are faulty,
-   and the new facilities in HTTP/1.1 are designed to rectify these
-   problems. The problem was that some existing HTTP/1.0 clients might
-   send Keep-Alive to a proxy server that doesn't understand
-   Connection, which would then erroneously forward it to the next
-   inbound server, which would establish the Keep-Alive connection and
-   result in a hung HTTP/1.0 proxy waiting for the close on the
-   response. The result is that HTTP/1.0 clients must be prevented from
-   using Keep-Alive when talking to proxies.
-</t>
-<t>
-   However, talking to proxies is the most important use of persistent
-   connections, so that prohibition is clearly unacceptable. Therefore,
-   we need some other mechanism for indicating a persistent connection
-   is desired, which is safe to use even when talking to an old proxy
-   that ignores Connection. Persistent connections are the default for
-   HTTP/1.1 messages; we introduce a new keyword (Connection: close) for
-   declaring non-persistence. See <xref target="header.connection"/>.
+   In HTTP/1.0, each connection is established by the client prior to the
+   request and closed by the server after sending the response. However, some
+   implementations implement the explicitly negotiated ("Keep-Alive") version
+   of persistent connections described in <xref x:sec="19.7.1" x:fmt="of"
+   target="RFC2068"/>.
+</t>
+<t>
+   Some clients and servers might wish to be compatible with these previous
+   approaches to persistent connections, by explicitly negotiating for them
+   with a "Connection: keep-alive" request header field. However, some
+   experimental implementations of HTTP/1.0 persistent connections are faulty;
+   for example, if a HTTP/1.0 proxy server doesn't understand Connection, it
+   will erroneously forward that header to the next inbound server, which
+   would result in a hung connection.
+</t>
+<t>
+   One attempted solution was the introduction of a Proxy-Connection header,
+   targeted specifically at proxies. In practice, this was also unworkable,
+   because proxies are often deployed in multiple layers, bringing about the
+   same problem discussed above.
+</t>
+<t>
+   As a result, clients are encouraged not to send the Proxy-Connection header 
+   in any requests.
+</t>
+<t>
+   Clients are also encouraged to consider the use of Connection: keep-alive
+   in requests carefully; while they can enable persistent connections with
+   HTTP/1.0 servers, clients using them need will need to monitor the
+   connection for "hung" requests (which indicate that the client ought stop
+   sending the header), and this mechanism ought not be used by clients at all
+   when a proxy is being used.
 </t>
 </section>
@@ -5892 +5895 @@
       "Intermediary rewriting of queries"
     </t>
+    <t>
+      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/158"/>:
+      "Proxy-Connection and Keep-Alive"
+    </t>
   </list>
 </t>