Subject: Re: Strange network problem with buffer space, huge lag, and so on
To: M Graff <>
From: Peter Postma <>
List: current-users
Date: 10/26/2006 19:55:48
On Thu, Oct 26, 2006 at 01:01:24AM -0500, M Graff wrote:
> Hash: SHA1
> M Graff wrote:
> > I have tried this both with and without pf filtering and ALTQ queueing.
> >  I have to keep pf active, however, since it is needed for NAT.
> Turns out I'm wrong there; I must have forgotten to reload the pf rules...
> With altq enabled, and a single default queue:
> altq on vlan9 cbq bandwidth 1100Kb queue { def_vlan9, ftp_vlan9,
> udp_vlan9, http_vlan9, ssh_vlan9, icmp_vlan9 }
> queue def_vlan9 on vlan9 bandwidth 100% cbq(default borrow red)
> I get this strange behavior where I get no buffer space messages, and
> terrible performance -- transferring a file out gives me 20% of my
> outgoing line speed.
> With no altq in my pf.conf, I get no control over my outgoing traffic
> characteristics, but I also don't get any lost packets due to buffer
> space, and I get nearly wire-speed transfers.

What seems to happen is that the queue gets full and ALTQ starts to drop
packets. That would also explain the slow performance (busy queue).
You can verify this with 'pfctl -sq -v'. An extra -v will show the
packet/byte rate for the queues. If there are indeed packets dropped,
then you might want to increase the queue limit with the 'qlimit' keyword.

Peter Postma