Flowgrind grinds flows among hosts in your network. It is a tool similar
to iperf, netperf to measure throughput and other metrics for TCP.
Flowgrind is split into two components: the flowgrind daemon and the
flowgrind controller. Using the controller, flows between any two systems
running the flowgrind daemon can be setup (third party tests). At regular
intervals during the test the controller collects and displays the
measured results from the daemons. It can run multiple flows at once with
the same or different settings and individually schedule every one.
Test and control connection can optionally be diverted to different interfaces.

WWW: http://launchpad.net/flowgrind