in Proceedings of the IEEE Workshop on the Management of Replicated Data, November 1990, Houston, Texas, USA.
There are essentially two classes of approaches to build reliable broadcast services: the clock-driven and the clock-less approach. The former rely on the existence of a global timebase, whereas the latter do not. Clock-driven and clock-less protocols have often been classified as equivalent to `synchronous' and `asynchronous', respectively. The clock as an implementation tool is, however, not mandatory to achieve synchronism.
By measuring the quality of synchronism by steadiness and tightness - a metrics that applies equally to both classes - we show that the criteria of suitability for real-time and fault-tolerance, can be extended to clock-less protocols.
Also available as INESC AR/25-90 (gzip postscript).