A generalized simulator for computer networks

Abstract

A generalized network simulator has been constructed to help investigate the performance of computer networks at a variety of levels. The simulator accounts for user-host, host-node (a node is a communications interface unit), and node-node interactions. The program is highly modular so that the user can change one level without affecting the others; this structure allows for innovation and efficient experimentation. Model validation has been a major consideration in the develop ment of the simulator. We have employed a formal procedure to validate models at the input-output level by comparing them to simple lumped models for a given experimental frame. The simulator can handle a variety of network structures and protocols. A particular network is described in terms of a schedul ing function, a grouping function, and a distance control matrix. Several network topologies and protocols have been simulated successfully. One problem with the modular approach is that it may lead to inefficient programs. Our simulator, for example, had to perform many scans of its events list because of the existence of numerous simultaneous events. We removed this inefficiency by introduc ing a new event scheduling routine based on a secondary key. The secondary key assigns priorities to simultaneous events.