EtherApe is a graphical network monitor for Unix modeled after Etherman.
Featuring link layer, IP and TCP modes, it displays network activity
graphically.  Hosts and links change in size with traffic.  Color coded
protocols display.  It supports Ethernet, FDDI, Token Ring, ISDN, PPP,
SLIP, and WLAN devices, plus several encapsulation formats.  It can
filter traffic to be shown, and can read packets from a file as well as
live from the network.  Node statistics can be exported.

WWW: http://etherape.sourceforge.net/