Reliability Aspects of Functional Communication

The object of our studies are functionally heterogeneous systems consisting of a large number of workstations and servers interconnected by a broadcast channel or a token passing ring. We focus on the communication issues in such systems. A functional communication model is proposed in [9] and several types of systems based upon the model are described in [7], [10], [11], and [12]. The functional communication model has three layers, the physical layer, the remote execution layer and the application layer, it is a model which supports directly the client-server paradigm. From the communication standpoint the system allows data packets with usual addresses, and packets with functional addresses. From the high level services point of view, the system consists of a pool of services, each service being identified by a unique service id. A client views the system as consisting of service groups every such group containing the set of servers capable to perform a given service. New servers may be added to a group or may be deleted from it without any change in the client representation of the system, as long as the group is not empty. The location of the server or the identity of the process performing the service are not relevant. Systems based upon the functional communication model are simpler, more reliable and secure.