Real-Time Group Communication in a Quasi-Synchronous System

Carlos Almeida and Paulo VerĂ­ssimo

INESC Technical Report (RT/23-95)


In this paper, we address the problem of having real-time group communication in a system that is not completely synchronous ( quasi-synchronous). This situation may happen when system load is not completely controlled and so, overload scenarios are not ruled out. In such scenarios, and for most of the networks used in this type of environments, temporal guarantees can only be made for the highest priority messages.

The paper describes a group communication protocol that provides a total temporal order in such an environment. It adapts to the uncertainty of the environment by means of a failure detection service, in order to be able to achieve its safety properties in a timely fashion. The protocol also tries to provide early-delivery while preserving its ordering property.

The paper also addresses some aspects related to fault handling and its relashionship to protocols providing several different qualities-of-service.

Also available as INESC RT/23-95 (gzip postscript).