We have a Debian linux based iptables firewall machine controlling access to the network. Occasionally we receive complaints that some users are having a hard time connecting to the Internet or that it is 'slow'. What we would like to do is be able to keep a historical graph for each host on the network (approx 50 computers) so when they complain we can look and see if there were any people using a lot of bandwidth at that time. Then we can decide what to do later.
Currently we use mrtg to graph the data in and out but we would like to be able to break that down per LAN computer. What tools are available to help us with that?