Ptolemy is a platform which allows the modeling and simulation of communication networks, signal processing, and various other applications. Its unique set of internal object-oriented interfaces allows it to merge heterogeneous descriptions of distinct system components into a unified simulation. This report concerns itself with asynchronous transfer mode (ATM), cell-relay network simulation and shows how the combination of three different domains (modes of system description) lends itself very well to this type of experiment: a synchronous dataflow (SDF) domain, a discrete-event (DE) domain, and a message queue (MQ) domain. The work presented follows on the details of a backbone network simulation described in [4]. It is not the goal of this report to focus on network-layer management and related issues; instead, it focuses on modeling techniques and performance evaluation of various popular, practical queueing disciplines for space-division packet switches. Ptolemy's naturalness for the simulation of such a heterogeneous environment will be demonstrated as well as its usefulness for analyzing network behavior and performance.