Efficient congestion control is critical to the operation of MPTCP, the Multipath extension of TCP. Congestion control in such an environment primarily aims at enhancing the cumulative TCP throughput over the available paths, while preserving TCP-friendliness by fairly sharing the available bandwidth with single-path TCP flows in each path. While most existing multipath congestion control algorithms fulfill the TCP-friendliness objective in their steady state, their throughput convergence latency is high, rendering them ineffective for short-lived flows. We have proposed Normalized Multipath Congestion Control (NMCC), an MPTCP congestion control algorithm that achieves TCP-friendliness faster, by normalizing the growth of individual sub-flow throughput rather than the throughput itself. As NMCC can become unfriendly when it experiences sparse congestion events, in this paper we introduce the extended NMCC (e-NMCC) protocol that caters for TCP-friendliness upon both throughput growth and throughput reduction epochs. We analytically characterize e-NMCC in terms of TCP-friendliness and responsiveness and compare it with alternative algorithms. Finally, we assess the performance of e-NMCC through experimentation with the htsim simulator and a real Linux implementation. Our results confirm that e-NMCC accelerates throughput convergence, thus ensuring TCP-friendliness regardless of connection duration and underlying network conditions.

中文翻译：

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多路径TCP的低延迟友好性

有效的拥塞控制对于MPTCP（TCP的多路径扩展）的操作至关重要。在这种环境中的拥塞控制主要旨在增强可用路径上的累积TCP吞吐量，同时通过与每个路径中的单路径TCP流公平共享可用带宽来保持TCP友好性。尽管大多数现有的多路径拥塞控制算法在其稳态下都可以实现TCP友好性目标，但它们的吞吐收敛等待时间却很高，从而使其对于短命流无效。我们已经提出归一化多径拥塞控制（NMCC），一种MPTCP拥塞控制算法，通过规范各个子流吞吐量（而非吞吐量本身）的增长来更快地实现TCP友好性。由于NMCC遇到稀疏的拥塞事件时可能变得不友好，因此在本文中，我们介绍了扩展NMCC（e-NMCC）协议，可同时满足吞吐量增长和吞吐量减少时期的TCP友好要求。我们通过TCP友好性和响应性来分析e-NMCC的特征，并将其与其他算法进行比较。最后，我们通过使用以下方法评估e-NMCC的性能htsim模拟器和真正的Linux实现。我们的结果证实，e-NMCC可以加速吞吐量收敛，从而确保TCP友好性，无论连接持续时间和基础网络条件如何。