Equal Opportunity Fairness in Resilient Packet Rings

Ring Ingress Aggregated with Spatial Reuse (RIAS) has been proposed as a fairness model for Resilient Packet Rings (RPR) where available bandwidth is allocated among traffic flows in max-min sense. In this paper, we show that in a feedback controlled system such as RPR, this may cause severe under-allocation for long-haul flows and may also result in degradation of total ring throughput. To overcome this problem, we introduce the concept of Equal Opportunity (EO) fairness. Application of this model for bandwidth management in RPR is studied and a new stateful distributed algorithm to calculate per-destination fair rates is developed. The proposed scheme is studied both analytically and through simulations. The simulation results show that using the proposed algorithm, intra-station fairness among local flows at every station is significantly improved. In some cases, imbalances up to 55% between long and short flows are completely removed. An improvement of up to 20% in total ring utilization is also observed.