bandwidth utilization

Hello

I have very busy linux server with a specific application which is network focused and I want to check is there any bottleneck on network layer and also wants to get application and/or os+application (a single value is enough for now). If I clean up that there is no network issue I could focus into other components of the server.

I could run tcpdump and also could exam it on wireshark I need tcpdump options and wireshark usage examples for my test ?

Any help would be appreciated

Thanks Murat