Parallel discrete-event simulation offers the promise of harnessing the computational power of multiple processors in order to reduce the time needed for simulation-based performance studies. In this paper, we investigate the use of optimistic parallel simulation techniques in simulating reliable multicast communication network protocols. Through empirical studies (using the TeD simulation programming language, the Georgia Tech time warp simulator, and a 12-processor SGI Challenge), we find that these parallelized simulations can run noticeably faster than a uniprocessor simulation and, in a number of cases, can make effective use of parallel resources. These results are somewhat surprising because reliable multicast protocols require considerable communication (and hence synchronization) among different network entities.