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Date:      Wed, 16 Aug 2006 19:49:44 +1000
From:      Peter Jeremy <peterjeremy@optushome.com.au>
To:        Bachilo Dmitry <root@solink.ru>
Cc:        freebsd-current@freebsd.org
Subject:   Re: throughput and interrupts
Message-ID:  <20060816094944.GC820@turion.vk2pj.dyndns.org>
In-Reply-To: <200608160959.23100.root@solink.ru>
References:  <200608151627.37828.root@solink.ru> <20060815130002.M45647@fledge.watson.org> <200608160959.23100.root@solink.ru>

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On Wed, 2006-Aug-16 09:59:22 +0700, Bachilo Dmitry wrote:
>Oh, it's natd. Now I see, but I just don't get it. I know that natd is not=
=20
>efficient but, as I've said, at home I have 9 or almost 10 MB/sec through =
the=20
>natd, while at this particular server I see only 3,7 MB maximum. I've trie=
d=20
>now to turn all the natting off and tried to download a file and got like =
9=20
>MB/sec, so it is natd who loads the system up.

natd runs in userland so every packet has to be pushed out to userland,
processed and pushed back into the kernel.  The vast majority of the
overhead is the userland/kernel transition so natd gives you a basically
fixed pps rate.  Your throughput will vary depending on the packet size.

>Someone advised me to use pf or ipnat, but I never did that before and hea=
rd=20
>that this nats have some limitations (like ipnat can't translate icmp pack=
ets=20
>or something).

Some time ago, I switched from natd to ipnat at work because the
overhead was getting too much.  (I've also switched hardware so I
can't give you direct performance comparisons).  I have found some
problems with IPfilter in -stable when combining ipfilter/ipnat,
stateful filtering and conditional NATing (ie a packet to B gets NAT'd
to C only if it came from A).  (The same combination works in IPfilter
3.x on Solaris.)  Normal filtering and NATing works OK.

--=20
Peter Jeremy

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