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Date:      Sun, 1 Apr 2001 22:36:43 +0200 (CEST)
From:      Bert Driehuis <driehuis@playbeing.org>
To:        "Jason T. Luttgens" <lucky@lansters.com>
Cc:        freebsd-stable@freebsd.org
Subject:   RE: Network performance question
Message-ID:  <Pine.BSI.4.21.0104012230300.4361-100000@c1111.nl.compuware.com>
In-Reply-To: <000001c0bae7$d315d910$0200010a@lucky>

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On Sun, 1 Apr 2001, Jason T. Luttgens wrote:

> >Send a predictable load to the device under test (say, include a
> >sequence number) and use that to determine packet loss (and, also
> >interesting, packet loss patterns).
> 
> Well, I thought that I was doing this by using a known set of data from the
> tcpdump I captured earlier and was replaying. Each time it replays, it is
> the same number of packets and payload content. The network I am testing on
> is isolated (not connected to anything else but these two computers).
> 
> I'm not sure I see the difference between what you describe and what I did.
> What do I need to do to create the environment you mention?

Number the packets sequentially, and read the tcpdump recording on the
receiving end. There is a huge difference between a driver crapping out
halfway through or one dropping every twelfth packet. I've seen Ethernet
drivers shut down for an X amount of time until a deadman timer restarts
it, and finding gaps in the data is an indication of that.

Cheers,

			-- Bert

-- 
Bert Driehuis -- driehuis@playbeing.org -- +31-20-3116119
If the only tool you've got is an axe, every problem looks like fun!


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