Shrinking Timestamp Sizes of Event Ordering Protocols

Almost all published work on causal ordering mechanisms assumes theoretically unbounded counters for timestamps, thus ignoring the real-world problem that arises if one is actually interested in an operable implementation, since unbounded counters simply cannot be realized. An argument for its justification often encountered states, that the counter size can be chosen such that counters practically do not overflow or wrap-around. For example, using matrix timestamps in a distributed computation involving not more than 50 processes and 32 bits per integer results in a timestamp size of almost 10 K-byte. In this paper, we present a solution, called Factorized Timestamp Approach (FTA) that substantially reduces the amount of piggybacked control information. It is based on introducing the notion of phases in which much smaller timestamps are used. Simulation results given in the paper show the suitability of this approach.