Scalable Fault Tolerance

Abst rac t . As communication networks grow, existing fault handling tools become increasingly unaffordable. In many cases the reason is that they involve global measures such as global time-outs or reset procedures, and their cost grows with the size of the network. Rather, for a fault handling mechanism to scale to large networks, it should involve local measures, or, at worse, fault local measures, i.e. measures the cost of which depends only on the number of failed nodes (which, thanks to today's technology, grows much slower than the networks). This decreases the recovery time and, moreover, often allows the non-faulty regions of the networks to continue their operation even during the recovery of the faulty parts. We describe several research ideas that lead in this direction.