Date: Fri, 30 Nov 2001 19:35:22 -0500 From: John Capo <jc@irbs.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Nate Williams <nate@yogotech.com>, Alexander Haderer <alexander.haderer@charite.de>, freebsd-hackers@FreeBSD.ORG Subject: Re: Found the problem, w/patch (was Re: FreeBSD performing worse than Linux?) Message-ID: <20011130193522.A36097@exuma.irbs.com> In-Reply-To: <200111302200.fAUM0hD27448@apollo.backplane.com>; from dillon@apollo.backplane.com on Fri, Nov 30, 2001 at 02:00:43PM -0800 References: <20011128153817.T61580@monorchid.lemis.com> <15364.38174.938500.946169@caddis.yogotech.com> <20011128104629.A43642@walton.maths.tcd.ie> <5.1.0.14.1.20011130181236.00a80160@postamt1.charite.de> <200111302047.fAUKlT811090@apollo.backplane.com> <200111302130.fAULUU324648@apollo.backplane.com> <15367.64883.390696.863120@caddis.yogotech.com> <200111302200.fAUM0hD27448@apollo.backplane.com>
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Quoting Matthew Dillon (dillon@apollo.backplane.com):
>
> The question here is... is it actually packet loss that is creating
> this issue for you and John, or is it something else? The only way
> to tell for sure is to run tcpdump on BOTH the client and server
> and then observe whether packet loss is occuring by comparing the dumps.
>
Packet loss is the problem for sure. I am dumping on the server and
client side.
http://www.irbs.net/server-dump.html
http://www.irbs.net/client-dump.html
In 60Ms the server pushed out about 200 segments. My test writes
1 byte at a time on an existing ssh conection so the payload per
segment is small, 48 bytes. (48 + IP + TCP) * 200 is around 17KB
in 60Ms which probably overflowed the frame switch queue. The
client is on a fractional T1, the server is on a 10Mb -> OC3
connection 1200 network miles away.
Jonathan Lemon pointed out in the TCP Anomalies thread that slow
start seems to be broken.
John Capo
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