Performance analysis of the Quick-Start TCP extension

Quick-Start is an experimental extension of the Transmission Control Protocol (TCP) that allows to speed up best effort data transfers. With Quick-Start, TCP hosts can request permission from the routers along a network path to send at a higher rate than allowed by the default TCP congestion control. The explicit router feedback avoids the time-consuming capacity probing by the TCP Slow-Start and is therefore particularly beneficial for underutilized paths with a high bandwidth-delay product. In this paper, the performance of the Quick-Start TCP extension is analyzed and the impact of router admission control strategies is studied. The main contribution is an analytical model that quantifies the improvement compared to default TCP Slow-Start. The model is validated by simulation results and by initial measurements with a Quick-Start implementation in the Linux operating system. Our results confirm that Quick-Start can significantly reduce the completion times of mid-sized data transfers.