IPtraf is described as 'IPTraf is a console-based network statistics utility for Linux. It gathers a variety of figures such as TCP connection packet and byte counts, interface statistics and activity indicators, TCP/UDP traffic breakdowns, and LAN station packet and byte counts' and is a Network Monitor in the Network & Admin category. There are three alternatives to IPtraf for Linux and Xfce. The best alternative is Nethogs, which is both free and Open Source. Other great apps like IPtraf are iftop (Free, Open Source) and IPtraf-ng (Free, Open Source).
iftop does for network usage what top(1) does for CPU usage. It listens to network traffic on a named interface and displays a table of current bandwidth usage by pairs of hosts. Handy for answering the question "why is our ADSL link so slow?".