Asynchronous protocols to meet real-time constraints: is it really sensible? How to proceed?

This paper investigates the use of asynchronous protocols to design and build middleware whose aim is to provide run-time support for soft real-time applications. A simple and general framework is described. This framework allows to take into account timeliness constraints of upper layer applications, while using an asynchronous protocol at the underlying level. When a timeliness constraint is about to be violated, the application layer is informed and can take appropriate measures. The deadline period can then be extended if the constraint is soft enough; in the other case, a default value can be used as a result. This framework can be seen as a bridge from asynchronous systems to synchronous ones. The proposed approach is illustrated with the consensus problem. This approach is investigated in the ARGO system we are implementing. The target applications of the ARGO middleware are telecommunication applications.