Bandwidth utilization tools? [closed]

What commercial or open-source tools are available to measure bandwidth utilization on a network? The tools should provide current and historical snapshots.


For monitoring, I would say something like Cacti, Ganglia or Munin. And for alerts, I would use Nagios.

For spot monitoring, ntop is useful for a quick graphical overview. One could always use netstat or tcpdump if you are into the command line stuff.