Sync-TCP: A new approach to high speed congestion control

As bandwidth in the Internet continues to grow, there will be more and more long fat network pipes with abundant residual bandwidth. At the same time, there is also a gradual and steady increase in the deployment of Internet endpoints equipped with different variants of high speed TCP. In this work, we first illustrate drawbacks associated with two widely deployed high speed TCP variants, namely: cubic TCP and compound TCP. We show that even with common and reasonable settings, problems can arise. Next, we present synchronized TCP (Sync-TCP), a new delay-based high speed congestion control (HSCC) algorithm. The approach taken by Sync-TCP is novel in the following ways. First, Sync-TCP exploits synchronization. The key insight of Sync-TCP is that if competing flows could detect the same congestion signal through queue delay, these flows can coordinate their congestion control behaviors. Second, using only the basic mechanism, Sync-TCP will yield to legacy TCP when congestion is detected. Hence, Sync-TCP is designed to not hurt applications using legacy TCP or interactive applications. We performed extensive simulation and some testbed evaluations to show that Sync-TCP achieves its design goals and it performs better than existing HSCC approaches including Fast TCP, Compound TCP and Cubic TCP, especially in the trade-off between throughput and friendliness.