[c-nsp] Total bandwidth usage

[Kanagaraj Krishna]

Hi,
   We are currently looking into usage based charges for our customers as an 
alternative option. Are there any free application thats is able to get total 
bandwidth usage (daily/weekly/monthly etc reports) which are port based? MRTG 
only gets bandwidth utilization rate and not the exact total utilization. I 
have a few questions:

- If an application monitors total utilization for a number of ports on 
  different devices wouldn't it be cpu, memory and bandwidth intensive?
- Are there any application that gathers bandwidth usage on intervals? If yes 
wouldn't it be a problem if the interface counters are reseted?

Thanks.

Regards,
Kanagaraj Krishna