Benchmarking networks is at best a tricky business. This page contains links and other information about network benchmarking
ipbench is a distributed network benchmarking suite written locally at UNSW, for the most part. It is hosted separately at http://ipbench.sourceforge.net
You can read a paper on the architecture Ian Wienand and Luke Macpherson; Ipbench: a framework for distributed network benchmarking; AUUG Winter Conference, Melbourne, Australia, September, 2004
Other interesting projects
Click is a "Modular Router Project" that plugs in components to make high performance, extensible, Linux based network routers.