Admission control for switched real-time Ethernet : scheduling analysis versus network calculus

Many approaches have been developed to give an estimation of the upper bound of the end-to-end delay or the response-time for real-time application, e.g., the Network Calculus (NC) model and the scheduling analysis. In this paper, we present an approach based on scheduling analysis to support guaranteed real-time services over standard switched Ethernet. Furthermore, we conduct a comparative study between these two admission control schemes, our novel algorithm and an NC-based algorithm. The simulation analysis shows that our feasibility analysis gives up to 50% higher utilization than the popular NC. Another advantage of our solution is that no additional hardware or software modification of the switch and the underlying standard. In our proposal, the traffic differentiation mechanism introduced by the IEEE 802.1D/Q standard and the standard hardware-implemented First Come First Served (FCFS) priority queuing are used in the switch and the source nodes. We have derived a feasibility analysis algorithm to ensure that the real-time requirements can be met. The algorithm also gives, as a sub-result, the needed buffer space in the end nodes and the switch. Moreover, our feasibility analysis supports variable-sized frames and switches with different bit-rates ports