IPTraf is a network monitoring utility and traffic analyzer for IP networks. It intercepts packets and returns data about captured the network traffic in various statistical facilities.
IPTraf comes with these major features:
An IP traffic monitor that shows TCP connection information (hosts, packet/byte counts, flags, window sizes), and color-coded information about other IP packets
Statistics (counts and load rates) for network interfaces in general and detailed views
Statistics per TCP/UDP port
Statistical breakdown according to packet sizes
A LAN host monitor that returns counts and loads per detected MAC address
A powerful filtering system for users to view only interesting traffic
An asynchronous DNS resolver for the IP traffic monitor
A text-based, full-color, menu-driven user interface suitable for use on all Linux systems with terminals, especially Linux consoles and color xterms
Fully software-based. No additional hardware required
Basic knowledge of the important TCP/IP protocols (IP, TCP, UDP, ICMP, etc.) is necessary for you to best understand the information generated by the program.