Here are some key features of "Iperf":

· TCP
· Measure bandwidth
· Report MSS/MTU size and observed read sizes
· Support for TCP window size via socket buffers
· Multi-threaded if pthreads or Win32 threads are available. Client and server can have multiple simultaneous connections
· UDP
· Client can create UDP streams of specified bandwidth
· Measure packet loss
· Measure delay jitter
· Multicast capable
· Multi-threaded if pthreads are available. Client and server can have multiple simultaneous connections. (This doesn't work in Windows.)
· Where appropriate, options can be specified with K (kilo-) and M (mega-) suffices. So 128K instead of 131072 bytes
· Can run for specified time, rather than a set amount of data to transfer
· Picks the best units for the size of data being reported
· Server handles multiple connections, rather than quitting after a single test
· Print periodic, intermediate bandwidth, jitter, and loss reports at specified intervals
· Run the server as a daemon (Check out Nettest for running it as a secure daemon)
· Run the server as a Windows NT Service
· Use representative streams to test out how link layer compression affects your achievable bandwidth
· A library of useful functions and C++ classes