Multipath transmission control protocol (MPTCP) is a promising transport layer protocol that enables a device to utilize multiple communication interfaces simultaneously, thereby achieving high throughput. A congestion control algorithm (CCA) employed in MPTCP constitutes a key part that controls the data flow through different subflows (SFs). There are two fundamental challenges associated with MPTCP CCAs. First, MPTCP flows should have an advantage over single-path flows; second, MPTCP flows should be fair, indicating that SFs sharing a common bottleneck should occupy a capacity fairly close to that occupied by a single-path flow. Several MPTCP CCAs have been developed; however, they have failed to satisfy these challenges in all scenarios. Recently, Google has introduced the bottleneck bandwidth and round-trip-time (BBR), a new CCA for single-path TCP, achieving high throughput with minimum delay by employing a network model. In the present paper, we propose a novel MPTCP CCA based on BBR named coupled multipath BBR (C-MPBBR) that satisfies the fundamental challenges by exploiting the concept of network modeling in BBR. C-MPBBR addresses the first challenge by closing the low-bandwidth SFs by tracking the delivery rate and bottleneck bandwidth (BtlBW). Then, it satisfies the second challenge through identifying those SFs that share a common bottleneck and dividing the BtlBW share corresponding to a SF among them. We implemented C-MPBBR in the Linux kernel, tested it on a wide range of scenarios by the Mininet emulation experiments, and the real-world Internet, and confirmed that the proposed C-MPBBR outperforms the existing MPTCP CCAs in terms of successfully satisfying the fundamental challenges by ensuring both throughput and fairness.

中文翻译：

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耦合多径 BBR (C-MPBBR)：多径 TCP 的高效拥塞控制算法

多路径传输控制协议 (MPTCP) 是一种很有前途的传输层协议，它使设备能够同时使用多个通信接口，从而实现高吞吐量。MPTCP 中采用的拥塞控制算法 (CCA) 构成了控制通过不同子流 (SF) 的数据流的关键部分。MPTCP CCA 有两个基本挑战。首先，MPTCP 流应该比单路径流有优势；其次，MPTCP 流应该是公平的，这表明共享一个公共瓶颈的 SF 所占据的容量应该与单路径流所占据的容量相当接近。已经开发了几个 MPTCP CCA；然而，他们未能在所有情况下满足这些挑战。最近，谷歌推出了瓶颈带宽和往返时间（BBR），一种用于单路径 TCP 的新 CCA，通过采用网络模型以最小延迟实现高吞吐量。在本文中，我们提出了一种基于 BBR 的新型 MPTCP CCA，称为耦合多径 BBR（C-MPBBR），它通过利用 BBR 中的网络建模概念来满足基本挑战。C-MPBBR 通过跟踪传输速率和瓶颈带宽 (BtlBW) 来关闭低带宽 SF，从而解决了第一个挑战。然后，它通过识别那些共享公共瓶颈的 SF 并在其中划分与 SF 对应的 BtlBW 份额来满足第二个挑战。我们在 Linux 内核中实现了 C-MPBBR，通过 Mininet 仿真实验和现实世界的互联网在广泛的场景中对其进行了测试，