HFCC: An Adaptive Congestion Control Algorithm Based on Explicit Hybrid Feedbacks

The high-throughput, low-latency, and reliable data delivery are fundamental demands of many networked applications, e.g. BitTorrent and Skype. But the inappropriate congestion control of TCPs, caused by the reactive and coarse- grained congestion feedbacks, brings the low link utilization, high queuing delay and frequent packet loss in high bandwidth-delay product network. To mitigate this issue, TCP variants have been developed. Thereinto, the load factor based congestion control (LFCC), e.g. VCP, BMCC, have shown the powerful capabilities to achieve better performances in terms of high link utilization, low persistent queue length, negligible packet loss, and fairness. However, due to the conservative increase and synchronized feedbacks, LFCC faces the slow convergence of the link utilization and inter-flow fairness. This could incur the large flow completion time of new-coming flows indirectly. To solve the issue of existing LFCCs, an asynchronous congestion control based on hybrid feedbacks, called HFCC, is proposed to achieve the faster convergence while keeping the features of LFCCs in this paper. Specifically, HFCC decreases the congestion window when the bottleneck link is in the high-load region and the flow rate exceeds the fair share of the bottleneck bandwidth, or the bottleneck link is in overload region. Otherwise, HFCC increases the congestion window. Note that an overlay coding method is developed in HFCC. To reduce the flow completion time, HFCC adopts an available bandwidth estimation method to speed up the data delivery in low-load region. The simulation results indicate that HFCC has the better performance and faster convergence than VCP, MLCP, and BMCC.