We propose an improved probabilistic method for reading remote clocks in systems subject
to unbounded communication delays and use this method to design a family of fault-tolerant
probabilistic internal clock synchronization protocols. The members of this family differ in
the failure classes they tolerate, from crash to arbitrary. Because of probabilistic reading, our
protocols achieve better synchronization precisions than those achievable by previously known
deterministic algorithms. Another advantage of the proposed protocols is that they use a linear,
instead of quadratic, number of messages, and that message exchanges are staggered in time
instead of all happening in narrow synchronization intervals. The envelope and drift rates of the
synchronized clocks are proven to be optimal.