PAPER Special Section on Networking Technologies for Overlay Networks TCP-Westwood Low-Priority for Overlay QoS Mechanism

An overlay traffic control is a way to provide flexible and deployable QoS mechanisms over existing networks, such as the Internet. While most of QoS mechanisms proposed so far require router supports, overlay QoS mechanisms rely on traffic control at transport layer without modifying existing routers in the network. Thus, traffic control algorithms, which are implemented at traffic sources or PEPs (Performance Enhancement Proxies), play a key role in an overlay QoS mechanism. In this paper, we propose an end-to-end prioritization scheme using TCP-Westwood Low-Priority (TCPW-LP), a low-priority traffic control scheme that maximizes the utilization of residual capacity without intrusion on coexisting foreground flows. Simulation and Internet measurement results show that TCPW-LP appropriately provides end-to-end low-priority service without any router supports. Under a wide range of buffer capacity and link error losses, TCPW-LP appropriately defers to foreground flows and better utilizes the residual capacity than other proposed priority schemes or even TCP Reno. Key words