SelfS — A real-time protocol for virtual ring topologies

Real-time automation systems have evolved from centrally controlled sensor-actor systems to complex distributed computing systems. Therefore, the communication system becomes a crucial component that strongly influences performance. In this paper we present a simple distributed communication protocol that meets hard real-time constraints without requiring complex synchronization mechanisms. An advantage of the distributed protocol is that network planning can be reduced to a minimum. The protocol is based on virtual rings and can be easily embedded into arbitrary network topologies. Besides a detailed evaluation and analysis of the protocol, the paper includes lower bounds on jitter and performance for arbitrary communication patterns.