Iperf : Testing the limits of your network

While tools to measure network performance, such as ttcp, exist, most are very old and have confusing options. Iperf was developed as a modern alternative for measuring TCP and UDP bandwidth performance.

Iperf is a tool to measure maximum TCP bandwidth, allowing the tuning of various parameters and UDP characteristics. Iperf reports bandwidth, delay jitter, datagram loss.

Multi Platform supports.

http://dast.nlanr.net/Projects/Iperf/