Network Pipemeter is a tool for measuring available bandwidth
between hosts. It is also useful to generate network traffic for
testing purposes. It operates in client/server mode, is able to
handle multiple parallel traffic streams, reports periodic partial
statistics along the testing, and supports IPv6. It has been
tested under Linux, FreeBSD, and Solaris.

'nepim' is similar to other tools like Iperf and Netperf.

Default test evaluates unidirectional, server-to-client
TCP bandwidth. It is used as follows:

server$ nepim
client$ nepim -c server-ip-address

Several command-line options can customize the
default behavior.

Further details at home site: http://www.nongnu.org/nepim/