Evaluating the overheads of source-directed quality-of-service routing

Quality-of-service (QoS) routing satisfies application performance requirements and optimizes network resource usage but effective path-selection schemes require the distribution of link-state information, which can impose a significant burden on the bandwidth and processing resources in the network. We investigate the fundamental trade-off between network overheads and the quality of routing decisions in the context of the source-directed link-state routing protocols proposed for future IP and ATM networks. Through extensive simulation experiments with several representative network topologies and traffic patterns, we uncover the effects of stale link-state information, random fluctuations in traffic load, and variations of the link-cost metric on the routing and signalling overheads. The paper concludes by summarizing our key results as a list of guidelines for designing efficient quality-of-service routing policies in large backbone networks.