PERFORMANCE OF A ROBUST MULTIPLE-RING, MULTIPLE-TOKEN NETWORK

Analytical and simulation studies of multiple-ring Token Ring Networks (TRNs) in which all nodes are connected to all rings [4,5] show that the packet transfer delay improves with the number of rings connected to each node. However, such multiple-ring TRNs are not economically feasible as the cost of the ring interface increases with the number of rings. Each node must provide a separate transceiver and Medium Access Control (MAC) entity for each ring. In this thesis, we study the performance of a novel configuration of a multiple-ring TRN which requires only two transceivers and two MAC entities at each node. The restriction to having just two transceivers and two MAC entities at each node will be economically viable considering the commerical success of Fiber Distrubuted Data Interface (FDDI) networks. We show that such a network is suitable for use in an environment in which the traffic patterns are clustered. For a quantitaive comparison ot the multiple-ring network, we also study the performance of a doule-ring TRN with a clustered traffic pattern, where transmission priority on each ring is given to intracluster packets. However, we find that this double-ring TRN offers no significant performance improvements over a normal double-ring TRN. By comparing the average packet delays of the multiple-ring TRN with those of the double-ring TRN with prioritised clustered traffic, we show that the former offers significant improvements in delay performance over the latter when the network traffic pattern is highly clustered with several clusters of nodes. Performance is studied in terms of the average packet transfer delay through mathematical formulation and computer simulation. It is shown that for random traffic, the overal delay performance of the network is close to the performance of the double-ring TRN, while the delay performance of this network for intracluster traffic is much better than that of the double-ring TRN. For clustered traffic, the performance of this network is better than that of the double-ring TRN for all cases.

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• WONG TUNG CHONG