The NT Testing TCP Tool is a handy little tool for testing the throughput between two servers – and it’s free! It’s available to download here: http://www.microsoft.com/whdc/device/network/TCP_tool.mspx
First, you need to install the MSI on both ends – for the sake of this, say SERVER1 and SERVER2. Once you’ve installed it on the server, navigate to \Program Files\Microsoft Corporation\NT Testing TCP Tool\, you should see a few copies of the tool for different architectures. Locate the correct .exe for you architecture and rename it to ntttcps.exe. Copy this and rename it to ntttcpr.exe – these form the sender and receiver parts of the tool.