Real-time data management with clock-less reliable broadcast protocols

Paulo VerĂ­ssimo

in Proceedings of the IEEE Workshop on the Management of Replicated Data, November 1990, Houston, Texas, USA.


Distributed applications relying on replication of data objects in several sites are becoming popular. One key to their success is that they rely on reliable broadcast/multicast protocols.

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).