A token-based delay optimal algorithm for mutual exclusion in distributed systems

In this paper, we present a token-based mutual exclusion algorithm for arbitrary topologies. This algorithm makes use of the network topology and site information held by each node to achieve an optimal performance. It reduces the delay in accessing the CS by allowing the token to service the requesting site which fall on-route its destination. This technique reduces the delay to a considerable extent specially at high loads. Moreover, in this algorithm, special messages called token location propagators are used to disseminate token's information faster and wider in the network. The performance of the proposed algorithm is evaluated and compared with Helary et al.'s algorithm [J. Helary, N. Plozeau, M. Raynal, A distributed algorithm for mutual exclusion in an arbitrary network, Computer Journal, 31 (4) 289-295, August 1988.] and Yan et al.'s algorithm [Y. Yan, X. Zhang, H. Yang, A fast token chasing mutual exclusion algorithm in arbitrary network topologies, Journal of Parallel and Distributed Computing 35 (1996) 156-172.]. The effect of increasing the connectivity of the network topology on the performance was also studied. The experimental results show that the proposed algorithm has the best performance specially at high loads and on topologies with low connectivity. (C) 1999 Elsevier Science B.V. All rights reserved.