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Date:      Wed, 17 Nov 1999  1:20:35 UTC-0800
From:      Mark McCutcheon <>
Subject:   Re: Bandwidth Capping fore ATM circuits?
Message-ID:  <"16609*"@MHS>

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On Wed, 17 Nov 1999 12:19:56 UTC+1000 George Michaelson
  <> wrote:

> I have a 2-PVC network config between two sites
> using Fore PCA200e cards. Well, its one PVC between
> the sites, and one additional PVC at the "main" site
> to provide edge connect into an Internet cloud.
> My backend network provider (campus networking) reports
> that I am exceeding their bandwidth allocations for the
> inter-site PVC, and the behaviour I see is that FTP downloads
> stall badly (presumably because TCP sees horrendous drop rate)
> I can't see any code clues to how I can do capped bandwidth stuff
> on this setup.
> Help! I need to make a 155mbps edge device behave "well" on 24mbps 
> core network bandwidth...

I imagine you're using the HARP ATM networking code supplied with
current versions of FreeBSD.  I haven't used it but understand that
it does not provide native traffic control facilities.  If you need
to do native ATM bandwidth management, that's a problem.  If you
can use IP-level bandwidth control, 2 means suggest themselves:

a) Luigi Rizzo's dummynet pipes under ipfw (man pages in current
versions) - haven't used it but there are favourable reports.  See

b) Kenjiro Cho's Alternate Queuing (ALTQ) with Class-Based Queuing
(CBQ) allows close control of bandwidth in IP flows.  Have used
this and it works well with 100BaseT.  However, it needs to modify
the output NIC drivers, and in earlier versions only knew about
Adaptec/Efficient ATM NICs with Chuck Cranor's BSD ATM.  You could
see whether the current release has support for Fore NICs and HARP
ATM code....

Hope this helps,


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