Prioritized protocols for multi-bus local area networks

M-CSMA/CD protocols with priority schemes are presented. Specifically, the basic priority scheme for M-CSMA/CD protocol proposed by M.H. Abdelaziz and R.L. Pickholtz (1984) are considered, and two improved priority schemes which given better channel resource utilization are presented. In the basic scheme, the low-priority messages can only be transmitted if the number of sensed idle channels exceeds a threshold value. In the first improved priority scheme there is a retransmission number threshold value for the lower priority messages. If the number of retransmissions of a lower priority message exceeds the threshold value, then the priority of that message is raised to that of the next higher class. In the second improved priority scheme a waiting time threshold value is set for each of the lower priority classes. The threshold value is obtained from the throughput-versus-delay curve for the basic priority scheme. If the waiting time of a packet exceeds the threshold value for its priority class, then the priority of that message is raised to that of the next higher class