"Linux is an excellent platform for network administration. If
you want to monitor your network traffic, you can find many
tools--some accessible from a Web interface, others using a
graphical interface--but nothing beats the speed of the command
line. Command-line tools are also useful in shell scripts, where
they can help you perform complex tasks. Here's a handful of my
favorites for monitoring network traffic.
"Atop is a system and process manager that displays network
traffic, along with other useful information such as CPU
consumption, memory usage, and a process list..."