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Date:      Thu, 5 Mar 2009 13:32:32 +0300
From:      Oleg Bulyzhin <oleg@FreeBSD.org>
To:        Sebastian Mellmann <sebastian.mellmann@net.t-labs.tu-berlin.de>
Cc:        freebsd-ipfw@freebsd.org
Subject:   Re: ipfw (dummynet) adds delay, but not configured to do so
Message-ID:  <20090305103232.GA19726@lath.rinet.ru>
In-Reply-To: <49AED3B1.1060209@net.t-labs.tu-berlin.de>
References:  <49AED3B1.1060209@net.t-labs.tu-berlin.de>

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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
> 
> When I do a simple ping from one machine to another (actually the
> FreeBSD machine is between those machines), I can see a delay of ~2ms.
> Without any rules/pipes I've got under 1ms delay.
> 
> The question is:
> Why do I have such a "high" delay though I didn't configure any "delay"
> in my pipe?
> Where does this additional millisecond come from (processing delay for
> the packet in the pipe?)?
> If I configure another rule (or like 10 more rules) that matches the
> packet, I can see the delay increasing.
> For example a delay of ~20ms, when I configure 10 pipes.
> Am I doing something wrong?
> 
> Thanks in advance for any help and please tell me if you need additional
> informations (e.g. kernel configuration).
> 
> 
> Regards,
> Sebastian M.
> 
> 
> _______________________________________________
> freebsd-ipfw@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-ipfw
> To unsubscribe, send any mail to "freebsd-ipfw-unsubscribe@freebsd.org"

If you have 7.1R or 6.4R setting net.inet.ip.dummynet.io_fast=1 will probably
reduce latency.

-- 
Oleg.

================================================================
=== Oleg Bulyzhin -- OBUL-RIPN -- OBUL-RIPE -- oleg@rinet.ru ===
================================================================




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