Dr Paul Ashton Lecturer, Department of Computer Science, University of Canterbury Abstract: In a distributed system each computer has its own local clock. Each clock drifts at a close to linear rate from physical (universal) time. Some applications require that the clocks of the computers within a distributed system be synchronised to within some maximum error. Many programs exist to maintain synchronisation. Clock corrections are calculated based on timestamps exchanged in messages. An alternative that can be used in some measurement applications is to correct timestamps after recording during data analysis. Several "off-line" clock synchronisation algorithms have been developed for this purpose. We have developed a test bed that allows clock offsets to be measured very accurately (the accuracy achieved is sub-microsecond). A number of clock synchronisation programs have been interfaced to the test bed (xntp, timed, some off-line algorithms), and some preliminary experiments done. This talk describes the test bed, discusses how programs are interfaced to it, and presents some initial results. When: Friday, 1.00 pm, 18 September 1998 Where: Castle C