Network Monitoring Software

[Mongrel]

So my fraternity has a network system for internet and connection to all of each others computers. I need a suggestion for a software program that will enabel me to monitor all ip addresses connected to our network, tell me how much bandwidth they are using etc. This software also needs to be able to limit peoples bandwidth. Do you have any suggestions?

 

[Cleric7x9]

here is a good place to start:
http://en.wikipedia.org/wiki/Network_traffic_measurement