Iperf is a network measurement tool/probe to make TCP and UDP throughput measurements. Miperf is simply the same tool but used for measurements using multiple streams. The home page is at NLANR's Iperf Site together with documentation. It is maintained and there is a mailing list for discussions and problems.
Experience:
One problem with iperf is that it sometimes hangs up. This is especially true for using it in multi stream mode where a thread/stream may not properly terminate resulting in hung sockets and the eventual necessity to reboot the host since too many sockets are in use.
In general we recommend using thrulay instead