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Date:      Thu, 6 Jun 2002 13:34:34 +0200
From:      "Patrick O'Reilly" <bsd@perimeter.co.za>
To:        "FreeBSD Question List" <freebsd-questions@freebsd.org>
Subject:   Voice QOS issue using ipfw/dummynet
Message-ID:  <000501c20d4e$250f11f0$b50d030a@PATRICK>

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Hi all.

I am trying to run some voice over an IP link using some devices which
convert voice to IP and back again.  The IP stream is then passing over
a 64k data line which has a FreeBSD gateway at each end.

Everything is fine when the first 2 voice channels are open, but once
the 3rd, then 4th channels are open the Quality starts to degrade.  The
voice supposedly only requires about 8k per channel, so even with 4
channels open the line should only be running at about 50% of capacity.

I have built the kernels with HZ=1000 just in case the clock granularity
was a problem, but that did not help at all.  Anyway, at present the
ipfw rules are passing the voice traffic without even using a dummynet
pipe, so the HZ setting might be inconsequential.

Does anyone have any experience with a similar combination of
requirements, and have some advice for me?

The gateways are running FreeBSD 4.5-RELEASE.  They are not doing any
other work, and the data line was not in use for any other data during
testing of the voice issues.  I am not sure what other technical info
might be relevant to this issue, so please ask and I'll fill in as
required.

Regards,
Patrick O'Reilly.
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