This thesis presents a modular, general-purpose interconnection network simulator called NETSIM developed as an extension to YACSIM, a C-language based process-oriented discrete event simulator. NETSIM is capable of simulating a wide range of switch architectures and network topologies. A NETSIM model can be simulated in a stand-alone mode with the network traffic generated by stochastic processes, or it can be used as an integral part of PARCSIM in an execution-driven simulation environment. This work emphasizes simulating complex switching schemes like wormhole routing efficiently. A detailed model for wormhole routing is implemented using two different techniques, and their relative advantages are evaluated. The thesis also presents four approximate models for simulating wormhole routing and evaluates the tradeoff between speedup and the accuracy of the approximate models. This thesis also develops a validation model for the iPSC/860 interconnection network using the NETSIM primitives, and evaluates the accuracy of the model in predicting the message latencies for the iPSC/860 system.