Performance comparison of two CSMA/CD systems with prioritized retransmission

For efficient processing of various types of traffic in LAN's, the introduction of a priority mechanism is considered to be effective. This paper considers nonpersistent CSMA/CD systems with a new priority mechanism, and derives the throughput and the average response time for each priority class by using the imbedded Markov chain method. The priority structure is achieved by assigning higher exponential retransmission rates to higher priority classes. As for the basis of priority assignment, we analyze two mathematical models: one is terminal-based and the other is message-based. Because the models allow feedback of packets, we can apply our results to error-prone CSMA/CD systems, also. Numerical results show that the simple priority mechanism works effectively, and clarify the differences between the terminal-based system and the message-based system.