This is iperf3, a tool for measuring Internet bandwidth performance.

iperf3 should work on Linux, FreeBSD, and Mac OSX

Prerequisites:
   libuuid: this is not installed by default for Debian/Ubuntu Systems
   to install: apt-get install uuid-dev

To build, just type 'make'  (or 'gmake' on FreeBSD)

For more information see: http://code.google.com/p/iperf/

Note that iperf3 is NOT backwards compatible with iperf2.