Efficient fault-tolerant routing algorithms for forward loop backward hop networks

Forward loop backward hop (FLBH) networks, characterized by a forward loop connecting all the adjacent nodes and a backward loop connecting nodes separated by a distance of h hops, have a higher connectivity and therefore a higher potential for fault-tolerance than single-loop networks. How to devise efficient fault-tolerant routing algorithms is an important issue on designing FLBH networks. This paper proposes two new fault-tolerant routing algorithms. One is for optimal FLBH networks with h²=N, where N is the number of nodes. The other is for arbitrary FLBH networks (i.e., 1⩽h⩽N-1). Both algorithms are theoretically shown to be able to guarantee that any packet is sure to reach its destination even when a faulty node exists. At the same time, they are simple and merely require local knowledge. A simple and effective rule, called the balancing rule, is used to determine the next node to which the incoming packet should be forwarded. The balancing rule enables the algorithms to find the shortest path between the source and the destination in most cases despite the presence of network faults. The results of computer simulations demonstrate that the average length of paths discovered by the authors´ algorithms is shorter than that found by other algorithms and is near optimal solution. As a result, these algorithms are suitable for implementation on practical local computer networks, especially on large ones