On the Reliability of IEEE 802.1CB FRER

The introduction of IEEE Time-sensitive Networking (TSN) enables the design of real-time and mission-critical networks based on Ethernet technologies. Apart from providing necessary tools for near-deterministic scheduling, TSN comes with further functionalities for configurability, security, and reliability. IEEE 802.1CB Frame Replication and Elimination (FRER) is the only protocol in the TSN toolbox for adding fault-tolerance via sending the same packets via redundant paths. Although its core functions are defined by the standard, its effective use mainly depends on the actual deployment scenario and the path selection strategy. In this paper, we show that FRER can induce unintentional elimination of packets packets when the paths chosen for a particular packet flow are non-disjoint. We propose the new metric reassurance that can be used in FRER path selection. Besides, we propose an additional enhancement to FRER that can prevent unintended packet eliminations independent from the deployment scenario. Our simulation results indicate that the reassurance-based path selection performs better than random or maximum-disjoint path selection in random failure scenarios.