Quantum assignment for QoS-aware AFDX network with deficit round robin

Avionics Full Duplex switched Ethernet (AFDX) is the de facto standard for the transmission of critical avionics flows. It is a specific switched Ethernet solution based on First-in First-out (FIFO) scheduling. Timing constraints have to be guaranteed for such critical flows. The worst-case traversal time analysis introduces some pessimism, leading to a very lightly loaded network: typically less than 10 % of the bandwidth is used. One solution to improve the utilisation of the network is to introduce Quality of Service (QoS) mechanisms. First, it can decrease worst-case delays for the most constrained avionics flows. Second less/non critical additional flows can be transmitted on the network with bounded impact on avionics ones. Deficit Round Robin (DRR) is such a QoS mechanism and it is envisioned for future avionics networks. An optimised WCTT analysis has been proposed for DRR on AFDX, based on network calculus. With DRR, the flow set is divided into classes and each class is allocated a quantum. In each round, transmissions are managed, based on these quanta. Thus delays are significantly impacted by quanta. The contribution of this paper is to propose an efficient quantum assignment for a set of critical avionics flow classes and at most one additional class with less/non critical flows.