Second-order rate-control based transport protocols

We propose an efficient flow and error control scheme for high-throughput transport protocols by using a second-order rate control, called the α-control, and a new sliding-window scheme for error control. The α-control minimizes the packet retransmissions by adjusting the rate-gain parameter to the variations in the number and round-trip times (RTTs) of cross-traffic flows that share the bottleneck. Using selective retransmission, the sliding-window scheme guarantees lossless transmission. By applying the α-control, the proposed scheme can drive the flow-controlled system to a retransmission-less equilibrium state. Using the fluid analysis, we establish the flow-control system model, obtain the greatest lower bound for the target buffer occupancy, and derive closed-form expressions for packet losses, loss rate, and link-transmission efficiency. We prove that the α-control is feasible and optimal linear control in terms of efficiency and fairness. Also presented are the extensive simulation results that confirm the analytical results, and demonstrate the superiority of the proposed scheme to others in dealing with the variations of cross-traffic flows sharing the same bottleneck and their RTTs, controlling packet losses/retransmissions, and achieving buffer-usage fairness as well as high throughput.