From owner-freebsd-net  Thu Oct 28  0: 5:27 1999
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To: "Craig Critchley" <craigc@nwlink.com>
Cc: "Garrett Wollman" <wollman@khavrinen.lcs.mit.edu>,
	net@FreeBSD.ORG
Subject: Re: FTP Net Performance 
In-reply-to: Your message of "Wed, 27 Oct 1999 22:58:22 PDT."
             <216001bf2109$718c8500$0201010a@fuzzer.com> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Thu, 28 Oct 1999 00:01:51 -0700
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>Ok, all the extra stuff is out of the machine, so it's down to motherboard,
>video card, and netcard.
>
>Still getting the same lousy throughput.
>
>I took another look at tcpdump, not the graphs, but the data itself.  It
>appears that Windows is sort of behind in its acks and eventually acks twice
>with the same sequence number.  When this happens, everybody holds their
>breath for a second and a half, then the BSD machine resends the
>double-acked packet.  This is my first tcpdump analysis effort, so if I have
>misinterpreted something, please let me know.  I just ran tcpdump with no
>switches after setting up BPF and captured the output.
>
>If this rings any bells with anyone, I would love to hear your theory.

   Uh, yeah, that very clearly shows that the Windows box is dropping packets
occasionally. Probably insufficient buffering (or just lousy network card) on
the Windows side.

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org
Creator of high-performance Internet servers - http://www.terasolutions.com
Pave the road of life with opportunities.


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