Fault tolerance and reliable routing in augmented hypercube architectures

Two schemes for augmenting hypercubes with spare nodes are presented. In both schemes, fault coverage is local in the sense that only the neighbors of the faulty nodes need to know about the faults. Routing in the presence of faults is accomplished by distributed algorithms that deliver messages reliably to their destination nodes. A message destined to a faulty node will be delivered to the spare node that replaces the faulty node. Both node and link failures may be accommodated in both schemes, and because no switches are used for reconfiguration, there is no assumptions about fault-free switches. The two schemes differ in complexity of interconnections between the spare nodes and the original cube nodes. More complex interconnections result in more flexible coverage algorithms and thus, more reliable systems. However, increased flexibility increases the complexity of the routing algorithm because more care has to be given to the possibility of messages looping in cycles and never reaching their destinations. The reliability of the fault coverage schemes and the efficiency of the routing algorithms are evaluated from simulation results.<>