Enforcing Consistency of Communication Requirements Updates in FTT-CAN

Traditional design approaches to safety-critical distributed systems, due to fault-tolerance reasons, have typically considered static cyclic table-based traffic scheduling. However, there is a growing demand for flexibility and integration, mainly to improve efficiency in the use of system resources, with the network playing a central role to support such properties. This calls for dynamic on-line traffic scheduling techniques so that dynamic communication requirements are adequately supported. The FTT-CAN protocol (Flexible Time-Triggered communication over Controller Area Network) has been developed specifically to deliver that kind of support with timeliness guarantees. It uses a master-slave approach with one or more master replicas for faulttolerance reasons. The communication requirements are held in a table, that is replicated in all masters. This paper considers the problem of updating the communication requirements while maintaining coherency and synchronization between the master and all its replicas. The paper also discusses the generalization of the proposed mechanism which can easily be adapted to other dynamic master-slave protocols.