ing use of sophisticated communications systems has led to many demands to shape scarce resources. Clearly, it is essential to quantify the performance of both existing systems and the ones at the design stages [1-5]. Today, the laptop personal computer has over a hundred times more computing power than the mainframe computer that was shared by tens, if not hundreds, of users a few decades ago. Evolving technologies, coupled with increasing demands for efficient and timely collection, processing, and dissemination of information, are leading to the fast telecommunications technologies such as Asynchronous Transfer Mode (ATM), Synchronous Optical Networks (SONET), Synchronous Digital Networks (SDH), Broadband-Integrated Services Digital Networks (B-ISDB), wireless networks, mobile computing and communications systems, and multimedia systems, among others [1-3]. Performance evaluation of computer and telecommunications systems has become an increasingly important issue, given their general pervasiveness. Evaluation of these systems is needed at every stage in the life cycle, including their design, manufacturing, sale/ purchase, use, upgrade, tuning, etc. There is no point in designing and implementing a new computer or telecommunications system that cannot compete with the existing systems in the market. Performance