Network Calculus-based Timing Analysis of AFDX networks with Strict Priority and TSN/BLS Shapers

Abstract

A homogeneous avionic communication architecture based on the AFDX supporting mixed-criticality applications will bring significant advantages, i.e., easier maintenance and reduced costs. To cope with this emerging issue, the AFDX may integrate multiple traffic classes: Safety-Critical Traffic (SCT) with hard real-time constraints, Rate-Constrained (RC) traffic requiring bounded latencies and Best Effort (BE) traffic with no delivery constraints. These traffic classes are managed based on a Non-Preemptive Strict Priority (NP-SP) Scheduler, where the highest priority traffic (SCT) is shaped with a Burst Limiting Shaper (BLS). The latter has been defined by the Time Sensitive Networking (TSN) task group to limit the impact of high priority flows on lower priority ones. This paper proposes a Network Calculus-based approach to compute the end-to-end delay bounds of SCT and RC classes. We consider the impact of the BLS and the multi-hop network architecture. We also provide proofs of service curves guaranteed to SCT and RC classes, needed to derive delay bounds with Network Calculus. The proposed approach is evaluated on a realistic AFDX configuration. Results show the efficiency of incorporating the TSN/BLS on top of a NP-SP scheduler in the AFDX to noticeably enhance the RC delay bounds while guaranteeing the SCT deadline, in comparison to an AFDX implementing only a NP-SP scheduler.