Optimal fault-tolerant routing in hypercubes using extended safety vectors

Reliable communication in cube-based multicomputers using the extended safety vector concept is studied. Each node in a cube-based multicomputer of dimension n is assorted with an extended safety vector of n bits, which is an approximated measure of the number and distribution of faults in the neighborhood. In the extended safety vector model, each node knows fault information within distance-2 and fault information outside distance-2 is coded in a special way based on the coded information of its neighbors. The extended safety vector of each node can be easily calculated through n-1 rounds of information exchanges among neighboring nodes. Optimal unicasting between two nodes is guaranteed if the kth bit of the safety vector of the source node is one, where k is the Hamming distance between the source and destination nodes. In addition, the extended safety vector can be used as a navigation tool to direct a message to its destination through a minimal path. Simulation results show a significant improvement in terms of optimal routing capability in a hypercube with faulty links using the proposed model, compared with the one using the original safety vector model.