Psimulator2 is a basic graphical network simulator that may be used to demonstrate basic IP networking concepts to students. It is not a fully-functional simulator because only a small sub-set of normal networking functionality is supported on each emulated node.
It will run on any system that supports Java; including Windows, Mac OS, and Linux. It offers the ability to “capture” and “play back” data traffic generated by the simulation. The packets are displayed on the GUI as envelopes that move through the network.