I don't know if this will help the person who started this topic, but there is a command line application that does what is requested. It is located in Networking(universe) section in Synaptic package manager. The name of the app is "nload" the description is as follows:
Nload is a console application which monitors network traffic and bandwidth
usage in real time. It displays the total amount of data that has been
transfered over a network device since the last reboot, the current bandwidth
usage, and the minimum, maximum, and average bandwidth usage measured
since it started.
If the user wants, it is also able to display two bars, similar to progress
bars, presenting the current load graphically. Support for displaying several
devices simultaneously is included.
