Enhancing Aggregate QoS through Alternate Routing

Recent work on differentiated services in the Internet has defined new notions of QoS that apply to aggregates of traffic in networks with coarse spatial granularity. Most proposals for differentiated services involve traffic control algorithms for aggregate service levels, packet marking and policing, and preferential treatment of marked packets in the network core. The issue of routing for enhancing aggregate QoS has not received a lot of attention. This study investigates the potential benefit of using alternate routing strategies in support of differentiated services. We propose a traffic control scheme, called Simple Alternate Routing (SAR), wherein portions of marked packet flows can be assigned to alternate paths through a Service Provider Network (SPN) in response to congestion feedback information. The scheme is simple, requiring only minor changes to the SPN border routers so that alternately routed packets can be tunneled via conventional paths to an intermediate bo..