On Scalable QoS Routing: Performance Evaluation of Topology Aggregation

A number of important questions remain concerning the scalability of networks with quality of service guarantees. We consider one of these questions: can QoS routing scale to large networks? To address this question, we evaluate performance of four QoS routing algorithms both with and without topology aggregation, based on simulations of relatively large, structured networks. Among our observations, we find --- contrary to intuition --- that topology aggregation does not always have a negative impact on routing performance. Aggregation can reduce the routing information fluctuation, increase stability, and thus benefit routing performance. We also propose two new methods of aggregating routing information. Our hybrid aggregation method has performance much better than conventional star aggregation and approaches unaggregated performance. Our weighted aggregation method, while intuitively appealing, offers mixed performance across topologies