Network utilization is an important performance indicator, in fact, there are four critical performance indicators: CPU, Memory, IO and Network.
Having said that, how do you know that is your network utilization?
I am sure you know that the Task Manager allow you to see the network utilization
In Vista you can also use the Reliability and Performance Monitor
But, what about windows performance counters? How can it be that Microsoft did not publish any performance counter for Network Utilization?
If you are asking yourself "why do I need Network Utilization performance counter?", here is an example:
Microsoft Visual Studio Team Edition for Testers supplies a load testing tool. During the load test you can collect information about critical resources from all machines in the lab. This way you will collect information about the CPU, Memory, IO and Network. Understanding how your network behaves is important. The load test tool is using Microsoft performance counters to gather this information.
Having said that, it is obvious that there needs to be basic information about the network utilization, right?
The solution will be to create a custom performance counter that will use the information that is available and will expose the network utilization.
You can read about the solution here.
You can get the code here.