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Date:      30 May 2002 17:24:07 -0700
From:      Jon Noack <noackjr@compgeek.com>
To:        freebsd-ipfw@freebsd.org
Subject:   Update: peer-to-peer asymmetric simulation
Message-ID:  <20020531002407.20594.cpmta@c015.snv.cp.net>

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I applied the patch from my original email and seem to have gotten it to work (after setting net.inet.ip.fw.one_pass=0).  Example rules:

For each <X> from 101 to 108

pipe N config bw 32Kbit/s delay 70ms queue 4Kbytes
add pipe N ip from 192.168.1.<X> to any
pipe N config bw 48Kbit/s queue 4Kbytes
add pipe N ip from any to 192.168.1.<X>

There are 2 pipes per host for a total of 16 pipes.

Limiting bandwidth down to 32Kbit/s seems to introduce an innate 20ms delay while 48Kbit/s introduces a delay of around 10ms (stayed constant at HZ=1000 and HZ=10000).  The above rules give me a consistent 200ms ping time between hosts {(70ms [+ 20ms innate] [+ 10ms innate]) * 2}.  Limiting bandwith to 128Kbit/s up and 1Mbit/s down introduces an innate delay of 10ms (for a full ping) about 2/3 of the time (average 7ms added over 60 pings).  This is due to queuing delay, correct (or is this uncertain due to the hack to bridge.c)?  Is there anything I can do to reduce this?

Finally (I ask again), why is this not enabled by default?  What am I risking with this?

Thanks again,
Jon Noack

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