.NET performance counters showing more than 100% network utilization

[bimalendug]

Hi All,

I'm using the .NET performance counters to calculate the network
utilization. But this value exceeds 100%.
In most of the cases, it is very similar to the one shown in the
task-manager. But when I try to measure the network utilization with a
particular utility that sends large data, then the values that I get
exceed 100%. Even in the task-manager it shows similar graph (graph
goes up above the 100% line and disappears and then sometimes comes
back to the 100% line and then it disappears again...)
Here is the formula that I use to calculate the network performance
(half-duplex):
%utilization = ((8*(dataSent + dataReceived))/bandwidth*time_in_sec)) *
100

Can anyone tell me what the problem is? Is it something expected?

Thanks & Regards
Bimalendu