Using constrained preemption to improve dropping fairness in optical burst switching networks

摘要

In this paper, we propose a new scheme to tackle the "beat down" unfairness problem in optical burst switching networks. In the new scheme, the control packets of bursts with higher preemptive metric value are allowed to preempt the channel resources reserved earlier for bursts with lower preemptive value. However, the control packets of preempted bursts continue to make wasted channel reservations in successive optical cross connects along the burst lightpaths and may also preempt other data bursts. Unchecked preemptions, therefore, can degrade the throughput of the network and induce reverse unfairness. Our scheme uses carefully designed constraints to avoid excessive wasted channel reservations, reduce cascaded useless preemptions, and maintain healthy throughput levels. The extensive simulation results show that the constrained preemption scheme improves fairness compared to previous methods without degrading network throughput.