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#158: Proxy-Connection and Keep-alive

From: Mark Nottingham <mnot@mnot.net>
Date: Mon, 28 Nov 2011 15:44:40 +1100
Message-Id: <C533CDDE-4EDB-4B4E-9697-1D365ACDB25C@mnot.net>
To: HTTP Working Group <ietf-http-wg@w3.org>
<http://trac.tools.ietf.org/wg/httpbis/trac/ticket/158>

Description: 

> The Keep-Alive header is referred to in a few places, but not defined as a HTTP/1.1 header. This should be addressed (e.g., in an appendix).
> 
> Likewise, Proxy-Connection is still (!) in common use, but has been deprecated for at least a decade. A few words in an appendix may encourage implementers to stop this practice.

We already have text in p1 about Keep-Alive, so it seemed best to just modify it slightly to also cover Proxy-Connection. I made a proposal on-ticke:

> Proposal - replace p1 A.1.2 with:
> 
> Most HTTP/1.0 implementations use a separate connection for each request. However, some implement persistent connections using the Keep-Alive negotiation mechanism described in Section 19.7.1 of [RFC2068].
> 
> In contrast, persistent connections are the default for HTTP/1.1; they do not need to be explicitly negotiated, as in HTTP/1.0. This is because there were various interoperability problems in the implementations of HTTP/1.0 persistent connections, especially when a proxy is involved.
> 
> For example, 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.
> 
> However, talking to proxies is the most important use of persistent connections, so that prohibition is clearly unacceptable. Some early attempts to correct this was to use the Proxy-Connection request header, but this approach was also unworkable, for similar reasons.
> 
> Therefore, some other mechanism for indicating a persistent connection was needed -- one that 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 Section 8.1.
> 
> As a result, HTTP/1.1 clients ought not to send the Proxy-Connection or Keep-Alive header; at best, they will waste bytes in requests, and at worst they can cause interoperability problems.

We should also probably register Proxy-Connection with a status of "obsoleted".

Comments?

--
Mark Nottingham   http://www.mnot.net/
Received on Monday, 28 November 2011 04:45:08 GMT

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