Time and Message-Efficient S-Based Consensus

Fabiola GREVE, Michel HURFIN, Raimundo MACEDO, Michel RAYNAL

To appear at Nineteenth Annual ACM SIGACT-SIGOPS Symposium on PRINCIPLES OF DISTRIBUTED COMPUTING (PODC 2000), Portland, Oregon, 16-19 July 2000


The class of "Strong" failure detectors (denoted S) includes all failure detectors that suspect all crashed processes and that do not suspect some (a priori unknown) process that never crashes. So, a failure detector that belongs to S is intrinsically unreliable as it can arbitrarily suspect correct processes. Several S-based consensus protocols have been designed. Some of them systematically require n computation rounds (n being the number of processes), each round involving n*n or n messages. Others allow early decision (i.e., the number of rounds depends only on the maximal number of crashes when there are no erroneous suspicions) but require each round to involve n*n messages. This brief annoucement presents an early deciding S-based consensus protocol each round of which involves 3(n-1) messages. So, the proposed protocol is particularly time and message-efficient. Moreover, it can easily be generalized to reduce the number of rounds at the price of an increase in the number of messages per round.