Network Monitoring Software

y guys,

Need a bit of advice. Our network currently contains around 15 2650 HP Procurve switches. These are all either running 1gig or fibre to a HP 4100GL. I am currently using Procurve manager to manage the swtiches using SNMP so i can check on port activity, status, configs etc. What I now need is some traffic management software. Procurve has the ability to do this but not in the way I want it to be done. I can look at traffic statistics on a given port, such as broadcasts, frames/sec etc but I want to be able to look at the network in a Topological format and see where traffic bottlenecks are occuring and things of this nature. As it stands now, I must wait for a problem to be reported and then sit there with the traffic monitor (which updates every 60 seconds so not live) and watch for frame traffic, excessive broadcasts etc.

Any ideas? Obviously prefer free software

Cheers

Jon