IP accounting on BSD box

I need to process the traffic on our network, finding how much data is used
by internal IP address.
I have been looking into tcpdump and other methods but cannot find a
definitive answer.

I can write a script to utilitise any input file if I can create an input
file with the right information.

I am trying to monitor web traffic mainly (port 80 & 443) plus some others.

Any ideas on the best methods?




Peter Campbell