Measuring Distributed Durations with Stable Errors

António Casimiro, Pedro Martins, Paulo Veríssimo and Luís Rodrigues

Selected sections of this report were published in the proceedings of the 22nd IEEE Real-Time Systems Symposium (RTSS 2001), London, UK, December 3-6, 2001.


The round-trip duration measurement technique is fundamental to solve many problems in asynchronous distributed systems. In essence, this technique provides the means for reading remote clocks with a known and bounded error}. Therefore, it is used as a fundamental building block in several clock synchronization algorithms. In general, the technique can be used to implement duration measurement services, such as the one of the Timely Computing Base model. In this paper we propose a new technique to measure distributed durations that minimizes the measurement error and is able to keep this error almost stable. The new technique can be used to improve the precision of remote clock reading in certain situations. We provide a protocol that implements this new technique and we present some evaluation results. The results clearly show that our solution is indeed better than existing ones.

Also available extended report (gzip postscript), (pdf) .

Luís Rodrigues