Traffic Monitor

[Spidey Knepscheld]

Hi

I am an ISP running FreeBSD as a firewall and as a Mail Server. My
problem is that I am not able to monitor the amount of traffic that user
are using on my network. 

My network looks like this: My Link comes in on a Cisco 805 from the
router it goes to the first NIC on the Firewall from the second NIC it
runs into a Cisco Catalyst and then to the network.On the catalyst I
mirrored the data coming from the network to the Firewall to one port
and I have a FreeBSD box on that port just to monitor the traffic.

What I am looking for is some app that could show me live what ip on my
network is utilizing what part of the bandwidth.I know there are a
million apps available but I need to see from IP ???? to IP ????   ????
kb/s and then see how much of the 256k is still available. Don't laugh
!!I have a 256k Diginet connection and I would like to see who is
killing my network. I do get live graphs from my upstream supplier but
it shows the line utilization from my router and not who is using what.

So I can't be proactive in solving speed issues I need to wait for it to
happen and then by a process of elimination disconnect segments of the
network and see when the graph drops.

I hope this makes sense to someone

thank you

Spidey