[e2e] Number of persistent connections per HTTP server?

Spencer Dawkins sdawkins at cynetanetworks.com
Thu Oct 10 08:10:56 PDT 2002

A couple of weeks ago, we were looking at the Mozilla source code, and tripped over http://lxr.mozilla.org/mozilla1.0/source/netwerk/protocol/http/src/nsHttpHandler.cpp, which (today - it does change!) includes

114     , mMaxConnections(24)
115     , mMaxConnectionsPerServer(8)
116     , mMaxPersistentConnectionsPerServer(2)
117     , mMaxPersistentConnectionsPerProxy(4)

and (later in the same file)

939     PRUint8 maxPersistentConnections =
940         ci->UsingHttpProxy() ? mMaxPersistentConnectionsPerProxy
941                              : mMaxPersistentConnectionsPerServer;

So it looked (from 50,000 feet) like Mozilla 1.0 does make a distinction between number of persistent connections to a server and number of persistent connections to a proxy. No, I haven't been through the code enough to know how far the implementation goes with this thought - but it seems to be part of the plan.

Mozilla seems to be implementing features like HTTP request pipelining, so this didn't surprise us a lot - we're just curious what science is behind the distinction between "number of connections per server" and "number of connections per proxy".

Any pointers?


(And, as an aside - the last posting on the HTTP mailing list was in September of last year - is there a more appropriate place to ask conceptual questions about HTTP mapping to TCP connections?)

-----Original Message-----
From: Prakash Khemani [mailto:khemani at netscaler.com]
Sent: Wednesday, October 09, 2002 11:51 PM
To: end2end-interest at postel.org
Subject: RE: [e2e] Number of persistent connections per HTTP server? 

Internet Explorer ver6 uses 2 persistent connections.
> Spencer,
> in 1996 or so there was a feeling that opening 4, say, parallel
> connections
> was evil.  possibly the http spec says "2" to mute the brickbats that
> might
> otherwise have been tossed its way because of the then prevailing
> i
> think 4 has always been the number most browsers use.  (i.e., i
> Netscape used 4 and others followed suit.)
> cheers, Greg Minshall

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