Something else installed to be able to poll a switch for bandwidth usage on its ports.
That usage should be saved per month (so maybe GBGraph?) and displayed in Gb's and/or mbits (95%).

The switch is a DLink DES-3226S, which supports SNMP.

I can do this for you for $20. You can e-mail me at ktims@gotroot.ca, or contact via MSN messenger at the same address.