1. A system for modeling and simulating a network including a plurality of nodes comprising: a processing system to model and simulate said network, said processing system including: a node model generation unit to produce a node model to enable said processing system to simulate a corresponding network node, wherein said node model includes a plurality of protocol layers each for performing a communications protocol function and a plurality of selectively configurable switches each disposed between and coupling corresponding ones of said protocol layers, and wherein at least one protocol layer includes a plurality of individually selectable functions selectable by a corresponding configurable switch to provide a desired behavior for said node during said simulation.