Here are some tools provided by the Ubuntu repos for network monitoring:

iftop - display bandwidth usage on an interface by host.

bmon -  portable bandwidth monitor and rate estimator, shows multiple interfaces at once.

slurm - network load monitor equipped with colored graphs.

tcptrack - reveals how much bandwidth is being used by what protocol (service/port), and destination the transmission is taking place to.

Each can be used for Specific monitoring or basic statistics.

Note Linux monitoring tools