A new fairness model for resilient packet rings

One of the main requirements in packet ring networks is to provide fairness in bandwidth allocation among the ring nodes. Each node must receive a fair share of the ring bandwidth and should not starve for an extended period of time. Due to the particular architecture of the packet rings, fairness models such as max-min fairness and proportional fairness are not suitable for these networks. Ring ingress aggregated with spatial reuse (RIAS) is a proposed model for packet rings. However, it lacks generality and intuition. In this paper, a new fairness model for ring networks called ring ingress aggregated max-min (RIAMM) fairness, is proposed. This model is invariant of the source behavior. We have analyzed conditions as well as feasibility criteria for this model. Considering resilient packet ring (RPR) as a particular case, we have studied the effect of source behaviors and fairness algorithms. Three main source behaviors, namely, MF (maximally feasible), FEP (feasible equal partitioning), and SC (single choke) are studied. We show that the FEP source behavior can result in a throughput loss of up to 17%, when traffic disparity exists. It is also shown that fairness algorithms with a slow convergence can result in permanent unfairness during a congestion period.