Centralized synchronization of clocks

摘要

A method for synchronizing clocks in a distributed computing system in the presence of faults. The condition to be renewed guarantees that all clocks of correct processors never deviate by more than some maximum amount. This condition is achieved by periodically resynchronizing the clocks so that the correct clocks do not deviate by more than some minimum deviation. In the process of resynchronization, a correct clock is never adjusted by more than a maximum amount during a period and it is never set back. The method requires that there is a previously agreed upon ordered list of all participants. At a specified time in the period, the first processor on the list attempts to synchronize all to its clock. The result of this is either a synchronization of all correct processors and their clocks to be within the desired tolerance or an agreement among all other correct processors that the first node on the list has failed. If the first fails, then the second tries and so on. Assuming at most f faulty components then one of the first f+1 attempts must succeed.