We propose a formal timing analysis of an extension of the AFDX standard, incorporating the TSN BLS shaper, to homogenize the avionics communication architecture, and enable the interconnection of different avionics domains with mixed-criticality levels, e.g., current AFDX traffic, Flight Control and In-Flight Entertainment. Existing Network Calculus models are limited to three classes, but applications with heterogeneous traffic require additional classes. Hence, we propose to generalize an existing Network Calculus model to do a worst-case timing analysis of an architecture with multiple BLS on multi-hop networks, to infer real-time bounds. Then, we conduct the performance analysis of such a proposal. First we evaluate the model on a simple 3-classes single-hop network to assess the sensitivity and tightness of the model, and compare it to existing models (CPA and Network Calculus). Secondly, we study a realistic AFDX configuration with six classes and two BLS. Finally, we compute a real use-case to add A350 flight control traffic to the AFDX. Results show the good properties of the generalized Network Calculus model compared to the CPA model and the efficiency of the extended AFDX to noticeably enhance the medium priority level delay bounds, while respecting the higher priority level constraints, in comparison with the current AFDX standard.
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.