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.

Vehicular ad hoc networks (VANET) aims to enhance vehicle navigation safety by providing an early warning system: any chance of accidents is informed through the wireless communication between vehicles. For the warning system to work, it is crucial that safety messages be reliably delivered to the target vehicles in a timely manner and thus reliable and timely data dissemination service is the key building block of VANET. Data mulling technique combined with three strategies, network codeing, erasure coding and repetition coding, is proposed for the reliable and timely data dissemination service. Particularly, vehicles in the opposite direction on a highway are exploited as data mules, mobile nodes physically delivering data to destinations, to overcome intermittent network connectivity cause by sparse vehicle traffic. Using analytic models, we show that in such a highway data mulling scenario the network coding based strategy outperforms erasure coding and repetition based strategies.