The authors analyze the reliability of two FDDI computer communication network architectures and make comparisons; these structures are a fault-tolerant dual-homing ring of trees and a failsoft ring of trees. They calculate the probability P[h(s,t)] that two arbitrarily positioned terminal stations (s and t) can communicate by deriving closed-form polynomial expressions for P[h(s,t)] in terms of component failure probabilities. The new expression for dual homing permits efficient quantitative reliability comparisons for networks with an arbitrary number of terminal stations, an arbitrary number of concentrator tree root pairs in the counter rotating dual ring, and varying numbers of ports in the concentrators.>

The reliability of three fiber distributed data interface (FDDI) network topologies is examined. The three interconnection topologies considered are a tree, a double ring, and a ring of trees. The reliability measure is terminal-pair reliability in which the probability P(h(s,t)) that two arbitrarily positioned terminal stations (s and t) can communicate with each other is calculated. For the three FDDI network topologies considered, closed-form expressions are obtained for worst-case reliability as a function of the stations' positions. The expressions are used to optimize the number of ports in and the topological interconnections of the wiring concentrators in order to achieve highest reliability for a given number of stations.>