I - MAC : A fair access protocol for passive asynchronous optical ring networks

Two major problems in a passive asynchronous optical ring network using CSMA/CA protocol are bandwidth fragmentation due to packet insertion process and unfair bandwidth access due to ring topology, which strongly drop the network performance. We introduce in this paper a CSMA/CA-based protocol with fairness improvement, (the so-called I-MAC for Improved Media Access Control), applied to passive asynchronous optical ring networks. On one hand, I-MAC efficiently counteracts the bandwidth fragmentation effect by intelligently controlling the packet insertion process at ring nodes. On the other hand, by adjusting the inter-transmission gap between consecutive local packets insertion at upstream ring nodes, I-MAC improves the fairness level of bandwidth access among ring nodes. This paper describes I-MAC protocol and analyzes its performance using Network Simulator tool. Simulation works shown that I-MAC is able to provide almost 100% fair bandwidth access (in terms of access delay and throughput) to all ring nodes even if the network is heavily loaded (i.e., offered ring load around 0,80), regardless of traffic partition on the ring. This considerably improves network performances and fairness index in comparison with classical