Fault-Local Distributed Mending

As communication networks grow, existing fault handling tools that involve global measures such as global time-outs or reset procedures become increasingly unaffordable, since their cost grows with the size of the network. Rather, for a fault handling mechanism to scale to large networks, its cost must depend only on the Ž number of failed nodes which, thanks to today’s technology, grows much more . slowly than the networks . Moreover, it should allow the nonfaulty regions of the networks to continue their operation even during the recovery of the faulty parts. This paper introduces the concepts fault locality and fault-locally mendable probŽ lems, which are problems for which there are correction algorithms applied after . Ž . faults whose cost depends only on the unknown number of faults. We show that any input-output problem is fault-locally mendable. The solution involves a novel technique combining data structures and ‘‘local votes’’ among nodes, which may be of interest in itself. Q 1999 Academic Press