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Date: Fri, 05 Feb 2010 19:34:49 +1100
From: Lawrence Stewart <lstewart@freebsd.org>
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To: Frank Schuster <frank.schuster01@web.de>
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Cc: freebsd-net@freebsd.org
Subject: Re: TCP debugging
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Hi Frank,

On 02/03/10 00:11, Frank Schuster wrote:
> Hello,
>
> I want to debug a tcp connection but I can't find how can I do this.
> I want to plot the cwnd and ssthresh over the time.
>
> I come from the "linux-world" and there is tcp_probe, but what can I do on Freebsd.
>
> 1.) Is this in freebsd possible and if it, how is it?

Have a look at the SIFTR tool I've been working on. You can grab it from 
here:

http://people.freebsd.org/~lstewart/patches/tcp_ffcaia2008/siftr_8.x.r195779.patch

I use it to do exactly the sort of thing you're trying to do.

> 2.) Which slow-start algorithm freebsd 8.0 is using as standard? (Reno, Cubic,...)

The slow start method used is regular RFC2851.

The congestion control algorithm is NewReno, but I also have patches 
enabling experimental use of other algorithms for research purposes. 
Happy to provide more pointers if you're interested.

Cheers,
Lawrence