Date: Mon, 23 Dec 2002 10:59:10 +0000 From: Mark Knight <markk@knigma.org> To: freebsd-stable@freebsd.org Subject: Strange cable TCP performance Message-ID: <kDqhAr1%2BxuB%2BEwN4@lap.knigma.org>
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I've a box running -stable dated 22nd December. The box contains two fxp interfaces. One interface is attached to my internal network (fxp0), and the other is attached directly to a newly installed Samsung SCM-140 cable modem (fxp1), and hence NTL's business broadband service. fxp1 is running natd, although removing the divert rule appears to make no difference to the symptoms described below. My broadband service claims 500kb/s download and 256kb/s upload. Download performance in fine as I expect. However, upload performance is not. Using ftp to put a 512kB file from this system, or wget to pull the same file either via http or ftp, speeds always start around the 30kB/s. However, this typically drops after a few seconds to 15-17kB/s. I've tried these tests at various times of day, to various well connected sites, and this is both repeatable and consistent. The same affect is observed with larger files; once the transfer rate has fallen, it does not usually increase. However, if I use either a Windows or a -current box, attached via fxp0 (or an0), and using the -stable box as their default router, upload performance is reliably increased to at least 27kB/s. In summary, systems other than the router itself appear to sustain approximately twice the upload rate of the -stable router itself. Various diagnostic outputs are located at: http://www.knigma.org/freebsd/cable/slow.txt A 512Kb test file containing random data is available at: http://www.shrewd.knigma.org/test/fullfile ftp://ftp.knigma.org/pub/download/fullfile I've tried tweaking a few inet sysctl's without noticeable affect, although I'll admit to not really knowing what I'm doing with these ;) Any advice appreciated, thank you, -- Mark A. R. Knight finger: markk@knigma.org Tel: +44 7973 410732 http://www.knigma.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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