Fault tolerant list scheduler for time-triggered communication in time-sensitive networks

Abstract

The performance and dependability of modern mission-critical systems significantly depends on the communication infrastructure. In this context, the Time-Sensitive Networking (TSN) task group addressed different requirements of cyber-physical systems such as timing and reliability constraints. TSN provides real-time capabilities through sharing a global time reference and employing transmission schedule tables called Gate Control Lists (GCL). On the other hand, TSN masks faulty behaviors within a system through a technique called Frame Replication and Elimination for Reliability (FRER). FRER fulfills the safety requirements of mission-critical systems by message replication and transmission of message replicas over redundant paths. The scheduling problem for the GCL synthesis is NP-complete. For simplification of the scheduling process, several state-of-the-art solutions provide schedulers for fault-free networks. However, this assumption is very optimistic and in practice networks experience different faulty-behaviors over time. This paper extends our heuristic TSN scheduler which was developed for fault-free TSN systems to support the FRER mechanism. Our fault-tolerant TSN scheduler focuses on enhancing the reliability of a mission-critical system while meeting the deadlines of time-critical jobs. To achieve this goal, we introduce a novel reliability analysis approach for a mission-critical system with a TSN communication infrastructure. This approach models and evaluates the reliability of a system based on the reliability of message transmissions between safety-critical jobs. The reliability of message transmissions is computed based on the reliability of the network components that form the forwarding paths. Thereby, our reliability model enables the system designers to plan networks more optimally.