An analytical model for fair rate calculation in resilient packet rings

Resilient packet ring (RPR) is a new medium access control (MAC) protocol for high-speed ring networks. It supports spatial reuse and, therefore, maintaining fairness among different nodes is a challenging task in RPR. To ensure fairness among nodes, a fairness algorithm is employed at each RPR node. In case of congestion, the fairness algorithm advertises a fair rate to all upstream nodes contributing to the congestion. In this paper, we develop an analytical model for fair rate calculation in the standard RPR fairness algorithm in the parking lot scenario. We first ignore the link propagation delay and model the system using a nonlinear discrete-time low-pass filter. We, then, consider the link propagation delay and develop a more realistic model. We verify our model by simulation results and analyze the effect of various parameters on the convergence time. Finally, we determine the low-pass filter coefficient to ensure that convergence time of the algorithm is within its minimum range