Unslotted CSMA-CD protocols with combined retransmission strategy for fiber optic bus and ring networks

Abstract

We present an unslotted 1-persistent carrier sense multiple access with collision detection (CSMA-CD) protocol with the combined preemptive-resume/-repeat-identical retransmission strategy for fiber optic bus and ring networks. Under this protocol, if the information field of a packet is preempted by upstream packets, its remaining portion is retransmitted with the identical header. However, when the header field of a packet is preempted, the packet is retransmitted from its beginning. Treating the bus and ring networks with M stations as an M -class priority queueing system and a two-class priority queueing system with the combined retransmision strategy, respectively, we show numerically that this protocol provides better delay-throughout performance than the unslotted CSMA-CD protocol in both networks, and it solves the instability problem of the unslotted CSMA-CD protocol in the ring network. To satisfy the fairness of equal delays among stations in the bus network, we next present the unslotted p i -persistent CSMA-CD protocol with the combined retransmision strategy, and determine the persistent probability p i and its delay performance. Simulation results are present to verify the analytical results.