A fault-tolerant token passing algorithm on tree networks

We present a self stabilizing token passing algorithm for a tree network. The algorithm is based on the 4 state mutual exclusion algorithm of E.W. Dijkstra (1974) and works under the distributed daemon model of execution. Although our algorithm relies upon an underlying tree network topology, it is not less general than the protocol by S. Huang and N. Chen (1993) since a spanning tree of a network can be obtained by a number of self stabilizing algorithms (A. Arora and M. Gouda, 1993; N. Chen et al., 1991; S. Huang and N. Chen, 1992; S. Sur and P.K. Srimani, 1992). Token passing on a spanning tree thus places no restriction on the topology of the underlying distributed system.