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Date: Wed, 4 Mar 2009 22:00:17 +0100
From: Luigi Rizzo <rizzo@iet.unipi.it>
To: Sebastian Mellmann <sebastian.mellmann@net.t-labs.tu-berlin.de>
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Cc: freebsd-ipfw@freebsd.org
Subject: Re: ipfw (dummynet) adds delay, but not configured to do so
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On Wed, Mar 04, 2009 at 08:17:05PM +0100, Sebastian Mellmann wrote:
> Hi everyone!
> 
> I hope this is the right place to ask.
> 
> I've got a IPFW ruleset that looks like this:
> 
> cmd=ipfw
> bottleneck_bandwidth=100Mbit/s
> in_if="em0"
> 
> $cmd pipe 500 config bw $bottleneck_bandwidth
> $cmd add pipe 500 all from any to any via $in_if

the delay that a packet experiences corresponds to len/bandwidth,
often rounded up to the next clock tick (1ms is the default).
You get one delay inbound, one delay outbound, so that's 2ms.

cheers
luigi