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Date:      Thu, 05 Mar 2009 19:58:32 +0100
From:      Sebastian Mellmann <sebastian.mellmann@net.t-labs.tu-berlin.de>
To:        Ian Smith <smithi@nimnet.asn.au>
Cc:        freebsd-ipfw@freebsd.org
Subject:   Re: ipfw (dummynet) adds delay, but not configured to do so
Message-ID:  <49B020D8.8070502@net.t-labs.tu-berlin.de>
In-Reply-To: <20090306033309.J71460@sola.nimnet.asn.au>
References:  <49AED3B1.1060209@net.t-labs.tu-berlin.de> <20090305124242.P71460@sola.nimnet.asn.au> <36832.62.206.221.107.1236237708.squirrel@anubis.getmyip.com> <20090306033309.J71460@sola.nimnet.asn.au>

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>  > > Also, without using a separate pipe for either traffic direction, you're
>  > > using 'half-duplex' mode, as well described in ipfw(8) TRAFFIC SHAPING.
>
> Paired pipes will speed things up.  Maybe not noticeably for pings (call 
> and response work half-duplex) but for esp TCP it could be considerable.
>
>   

How does this "pairing" of pipes work?
Couldn't find any documentation about it.

>  > > Output of 'sysctl net.inet.ip.fw.one_pass' and 'ipfw show' with your
>  > > example of using multiple pipes?
>  > 
>  > [root@ ~/ipfw]# sysctl net.inet.ip.fw.one_pass
>  > net.inet.ip.fw.one_pass: 0
>  > 
>  > [root@ ~/ipfw]# ipfw show
>  > 00010        0          0 allow ip from any to any via lo0
>  > 10000      122      11832 allow ip from any to any via em2
>  > 10100        0          0 pipe 100 ip from 192.168.5.0/26 to 192.168.7.0/24 in via em0
>  > 10200        0          0 pipe 200 ip from 192.168.7.0/24 to 192.168.5.0/26 out via em0
>  > 10300      342      28728 pipe 500 ip from any to any via em0
>  > 10400      359      36512 pipe 510 ip from any to any via em1
>  > 10500        0          0 pipe 300 udp from 80.80.80.1 to 60.60.60.1 src-port 4000 dst-port 4000 via em1
>  > 10600        0          0 pipe 305 udp from 60.60.60.1 to 80.80.80.1 src-port 4000 dst-port 4000 via em0
>  > 10700        0          0 pipe 310 udp from 80.80.80.1 to 60.60.60.1 src-port 4001 dst-port 4001 via em1
>  > 10800        0          0 pipe 315 udp from 60.60.60.1 to 80.80.80.1 src-port 4001 dst-port 4001 via em0
>  > 65535 14144748 9784372451 allow ip from any to any
>
> A note of caution: using 'via' unqualified can be tricky; 'via em0' on 
> the inbound pass is the same as 'in recv em0', but 'via em0' on the 
> outbound pass includes packets that came IN on em0 but are going out on 
> any interface, as well as those that came in on any interface that are 
> going OUT on em0.  I prefer specifying 'in recv' and 'out xmit' where 
> there might be any ambiguity; this usually works naturally with pipes, 
> where you'd normally have one pipe per flow direction anyway.
>
>   
Actually I'm using 'in recv' and 'out xmit', but it wasn't applied in
this example, but thanks for the hint again (you already mentioned that
on the freebsd-question mailing list I think ;-)).

> Hopefully increasing kern.hz solves your main issue, and worth trying 
> the new! net.inet.ip.dummynet.io_fast too.  Let us know your results?
>
>   

For now we will stick to the delay "issue" and see how it affects our
results.


> cheers, Ian
>   

Regards,
Sebastian



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