Comparison of AFDX and audio video bridging forwarding methods using network calculus approach

The embedded avionics system is a typical mission-critical and safety-critical system, and should ensure fulfillment of all constraints for all flows with individual timing requirements transmitted in networks. Scheduling strategies are used to meet this requirement, and different networking solutions have different approaches. AFDX (Avionics Full-DupleX Switched Ethernet) implements a SPQ (Strict Priority Queuing) scheduling strategy with two priority levels where large flow bursts from high priority data would lead to high delays for low priority flows. Ethernet-AVB (Audio Video Bridging) implements Credit-Based Shapers (CBS) on top of the SPQ mechanism, which can partly mitigate this problem. This kind of scheduling strategy could be considered in an avionics context for mix-criticality systems. In this paper, CBS and SPQ scheduling algorithms are compared especially from the worst-case criteria by using network calculus approach. Results show that compared with SPQ, CBS has a better anti-interference ability, though it would bring a bigger delay even from the worst-case prospective.