A fault tolerant protocol as an extension to a distributed mutual exclusion algorithm

In this paper, we present an extension to Kerry Raymond's tree based distributed mutual exclusion algorithm to make it fault tolerant. The algorithm uses a spanning tree of a computer network. With N nodes in the network the number of messages exchanged per critical section entry is typically O(log N). The novelty of the algorithm lies in each node holding information only about its immediate neighbors in the spanning tree. We basically present a protocol to make the algorithm tolerant to single node/link failure and associated network partition. This protocol assumes that the graph of the underlying network is biconnected. Basically we attempt reconfiguration of the tree after isolating the failed components. With this enhancement a significant number of cases in which the algorithm would have halted due to lack of communication paths, can be effectively handled by utilizing alternative communication paths now available, thus continuing to provide the mutual exclusion service.