How to Use the NTttcp Tool to Troubleshoot Network Performance in Windows

When troubleshooting network performance issues, it can be difficult to isolate network performance from that of other system components. Copying a file from one system to another, for example, also uses the memory and disk subsystems on both machines. There is a tool available from Microsoft designed to test only the network: NTttcp.

The latest version of NTttcp (v5.39 as of this writing) is available for download here. 

Usage Example: This command runs the tool as a receiver in asynchronous mode for 30 seconds, using four threads dynamically allocated across all processor cores, two outstanding I/O buffers, and a 64K buffer size:

ntttcp.exe -r -m 4,*,192.168.242.5 -l 64k -a 2 -t 30

This is the corresponding command on the sender:

ntttcp.exe -s -m 4,*,192.168.242.5 -l 64k -a 2 -t 30

Both commands include the same IP address: the address of the receiver.

The output of the tool, which can be saved as an XML file, gives detailed information about the total amount of data transferred, CPU usage, and total throughput during the test. This information can help determine whether a performance bottleneck is caused by the network or another component of the system in question.

There are a couple of important things to remember when using NTttcp:

• It must be run on both sides of a connection (a client and server, for example).
• In the previous version, it was necessary to rename the executable to specify whether it was to be run as a sender or receiver. This is no longer necessary in the new version, which uses the -s and -r switches for this purpose.

More information about NTttcp can be found here. An active Azure subscription is not required to use the tool.