In order to be TCP-friendly, the original Multipath TCP (MPTCP) congestion control algorithm is always restricted to gain no better throughput than a traditional single-path TCP on the best path. However, it is unable to maximize the throughput over all available paths when they do not go through a shared bottleneck. Also, bottleneck fairness based solutions detect the bottleneck and conduct different congestion control algorithms at different bottleneck sets to increase throughput while remaining fair to single TCP. However, existing solutions generally detect shared bottlenecks through delay correlation and loss correlation between two flows, which often lead to misjudgement in dynamic and complex network scenarios. Therefore, in this paper, we first propose a new Shared Bottleneck based Congestion Control scheme, called SB-CC, which leverages ECN (Explicit Congestion Notification) mechanism to detect shared bottlenecks among subflows and estimate the congestion degree of each subflow. Then, with the congestion degree, SB-CC balances the loads among all subflows, and smooths out congestion window fluctuation. Also, in order to prevent throughput degradation due to out-of-order packets, we propose a Shared Bottleneck based Forward Prediction packet Scheduling scheme, called SB-FPS. SB-FPS distributes data according to the window size changes of each subflow, and thus could more accurately schedule data in shared bottleneck scenarios. We implement our proposed scheme in the Linux kernel and simulation platform to evaluate the performance in different scenarios. Measurement results indicate that our scheme can detect the bottleneck more accurately and improve the overall network performance while still keeping bottleneck fairness.

中文翻译：

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基于共享瓶颈的多路径TCP拥塞控制和分组调度

为了对TCP友好，始终限制原始多路径TCP（MPTCP）拥塞控制算法，使其在最佳路径上没有获得比传统单路径TCP更好的吞吐量。但是，如果所有可用路径都没有遇到共享瓶颈，则无法最大化它们的吞吐量。同样，基于瓶颈公平性的解决方案可以检测到瓶颈，并在不同瓶颈集执行不同的拥塞控制算法，以提高吞吐量，同时保持对单个TCP的公平性。但是，现有的解决方案通常会通过两个流之间的延迟相关性和丢失相关性来检测共享瓶颈，这通常会导致在动态和复杂网络场景中进行错误判断。因此，在本文中，我们首先提出一种新的基于共享瓶颈的拥塞控制方案，称为SB-CC，它利用ECN（显式拥塞通知）机制来检测子流之间的共享瓶颈，并估计每个子流的拥塞程度。然后，通过拥塞程度，SB-CC平衡所有子流之间的负载，并消除拥塞窗口波动。此外，为了防止由于乱序数据包而导致吞吐量降低，我们提出了一种基于共享瓶颈的前向预测数据包调度方案，称为SB-FPS。SB-FPS根据每个子流的窗口大小变化分配数据，因此可以在共享瓶颈情况下更准确地调度数据。我们在Linux内核和仿真平台中实施我们提出的方案，以评估不同情况下的性能。