Performance of a dual-bus unidirectional broadcast network operating under probabilistic scheduling strategy

• Authors: B. Mukherjee
• Venue: SIGMETRICS '89 Proceedings of the 1989 ACM SIGMETRICS international conference on Measurement and modeling of computer systems
• Year: 1989

Recent advances in fiber optic technology (viz. its promise to provide information-carrying capacity in the Gpbs range over long repeater-free distances) has triggered tremendous activity in the study of unidirectional bus networks (because signal flow in the fiber is unidirectional). A popular network structure that has received significant attention is the Dual-bus Unidirectional Broadcast System (DUBS) network topology. Most of the access mechanism studied on this structure are based on round-robin scheduling (or some variation thereof). However since round-robin schemes suffer a loss of channel capacity because of their inter-round overhead (which can be significant for long high-speed buses), a probabilistic scheduling strategy, called pi-persistent protocol, has recently been proposed and studied for single channel unidirectional bus systems. Our concern here is to apply this probabilistic scheduling strategy to each bus in DUBS, and study the corresponding network performance. In so doing, we allow stations to buffer multiple packets, represent a station's queue size by a Markov chain model, and employ an independence assumption. We find that the average packet delay is bounded and the maximum network throughput approaches two pkt/slot with increasing buffer size. Further, the protocol's performance is insensitive to bus characteristics, and it appears to be a particularly well suited for fiber-optic network application requiring long distances and high bandwidth. Simulation results, which verify the analytical model, are also included.