Algorithms for o -line clock synchronisation

O -line clock synchronisation algorithms, in which synchronisation is performed by adjusting a collection of recorded timestamps, is suitable for use with many monitors for distributed systems. O -line synchronisation can often achieve very good synchronisation without the need for extra messages. The work described here builds on earlier work in this area [4] by introducing new synchronisation algorithms, developing ways of evaluating algorithms, and performing an extensive set of experiments based on ve di erent algorithms and a considerable amount of data collected by a monitor for Amoeba. The best algorithms achieve excellent synchronisation, and are used in the Amoeba monitor.