Date: Fri, 30 Nov 2001 19:41:26 -0500 From: Leo Bicknell <bicknell@ufp.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Mike Silbersack <silby@silby.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: TCP Performance Graphs Message-ID: <20011130194126.A969@ussenterprise.ufp.org> In-Reply-To: <200111302059.fAUKxrI19553@apollo.backplane.com>; from dillon@apollo.backplane.com on Fri, Nov 30, 2001 at 12:59:53PM -0800 References: <Pine.BSF.4.30.0111301523400.3797-100000@niwun.pair.com> <200111302059.fAUKxrI19553@apollo.backplane.com>
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On Fri, Nov 30, 2001 at 12:59:53PM -0800, Matthew Dillon wrote:
> The transmit side requires more thought. I did write that patch, and
> it does work, but it's too messy for my tastes. I would personally
> much rather rewrite it to (A) fix the RTT stored in the route tables
> and (B) adjust the transmit window based on that, which is a much less
> sophisticated patch (and less messy), but ought to work quite well
> in regards to transmit buffer management.
I think I tried this patch, and found some problems with it. As
I recall the problems were with extremely high bandwidth connections
(eg, I have two machines that can move 100Mbps FDX across country
(70ms latency), and when I tried the patch with that case performance
was "bad", in the sense that I got like 20Mbps, rather than 100,
like it should have allowed.
I believe I theorized at the time that the calculation code had a
term that ended up zero, or infinity or something with values that
large.
Sadly, at this moment I don't have test boxes on that path, but I
do now have test boxes behind an otherwise empty T1 that I can do
interesting things with (eg, WRED on or off, short queues, long
queues, artificial limits like CAR). I have a little time to do
testing (emphasis on little), if one or two people would like to
do more I can make the resources available, contact me privately.
--
Leo Bicknell - bicknell@ufp.org - CCIE 3440
PGP keys at http://www.ufp.org/~bicknell/
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