How to check whether network busy or not?

Question

Hello everyone,

I am writing a backend program which will upload some big files to another server and I want to detect whether current machine's network is busy or not (I want to use relative non-busy time of current machine to upload files, as I do not want to impact other network related task on the machine as the upload file task priority is low).

Does anyone have any idea about how to check whether current machine is busy with network I/O? Should I check some performance counters?

thanks in advance,
George