FreeBSD 5.3 Networking performance problem

[Chuck Swiger]

Andrew Seguin wrote:
> We have about 100 computers active, generating a stream of approximately
> 80-90K packets per minute for a load I estimate* to be a little under
> 10Mbps. Overall the firewall will need to filter for a /24 subnet.

OK.

> *Configuration:
>   Hardware:
> The firewall is a Celeron 900Mhz with 128MB ram (more on the way) with one
> rl and one sis based network cards.

My first suggestion would be to bin the rl NIC and replace it with an fxp or 
dc-based NIC.  Realtek NICs are infamous for working poorly or not working 
reliably at all under load.

[ ... ]
> I then tested with the whole school going through the firewall: very bad.
> packets were being droped and ping times were around 600ms. Internet was
> pretty much unuseable.

This report sounds consistent, although you could also have a bad cable or 
switch port, too.  It would be useful to you to look into the output of 
"netstat -i" and "netstat -s", and any statistics which might be available on 
your switches (if they have management & per-port stats).

-- 
-Chuck