Network on Chip (NoC) is a new paradigm for designing large and complex systems on chips (SoCs). In this paradigm, a packet switched network is provided for on-chip communication. The NoC paradigm provides the required scalability and reusability to reduce design time of SoCs. A NoC simulator is an important tool required to support development of designs based on a NoC architecture. In this paper, we describe the design of such a simulator using the ITU-T Specification Description Language (SDL). Features of SDL for representing structural hierarchy using blocks, concurrent processes and dynamic generation of processes, communication channels, user defined data types and timers are useful for modelling a NoC architecture at various levels of communication protocols. We use an event driven SDL simulator to carry out interesting experiments to evaluate various architectural options such as buffer size in switches, and their effect on the performance such as delay and packet loss.