Asynchronous Traffic Shaping and Redundancy: Avoiding Unbounded Latencies in In-Car Networks

Time-Sensitive Networking enhances Ethernet-based In-Vehicle Networks (IVNs) with real-time capabilities. Different traffic shaping algorithms have been proposed for time-critical communication, of which the Asynchronous Traffic Shaper (ATS) is an upcoming candidate. However, recent research has shown that ATS can introduce unbounded latencies when shaping traffic from non-FIFO systems. This impacts the applicability of ATS in IVNs, as these networks often use redundancy mechanisms, i.e. Frame Replication and Elimination for Reliability (FRER), that can cause non-FIFO behavior. In this paper, we approach the problem of accumulated delays from ATS by analyzing the scenarios that generate latency and by devising placement and configuration methods for ATS schedulers to prevent this behavior. We evaluate our approach in a simulation environment and show how it prevents conditions of unbounded delays. In an IVN simulation case study, we demonstrate the occurrence of unbounded latencies in a realistic scenario and validate the effectiveness of our solutions in avoiding them.