Performance of an Adaptive Routing Overlay under Dynamic Link Impairments

We propose an adaptive software routing overlay to improve the performance of TCP/IP-based internets over links with dynamic impairments. The routing overlay adaptively distributes traffic over a set of alternative paths based on real-time link status information provided by a system of network sensors. The routing overlay also provides explicit rate feedback to rate-aware TCP clients, allowing them to achieve higher throughputs than legacy clients under static link loss and delay impairments. We present performance results from a collection of Emulab experiments on simple network topologies with dynamic link impairments. The results show that the adaptive routing overlay achieves significantly higher bulk file transfer throughput than legacy systems in the presence of link impairments. Sensor-based adaptive routing provides substantial gains in TCP throughput even for legacy TCP clients. When rate-aware TCP clients are used, the performance gain of the adaptive routing overlay with respect to legacy systems improves dramatically.