MPTCP is a new transport protocol that enables mobile devices to use multiple physical paths simultaneously through several network interfaces, such as WiFi and Cellular. However, wireless path capacities change frequently in the mobile environments, causing challenges for path selection. For example, WiFi associated paths often become poor as devices walk away, since WiFi has intermittent connectivity caused by the short signal coverage and stochastic interference. MPTCP's native decision based on hysteretic TCP-layer estimation will miss the real switching point of wireless quality, which may cumulate packets on the broken path and causes serious packets reinjection. Through analyzing a unique dataset in the wild, we quantitatively study the impact of MAC-layer factors on the aggregated performance of MPTCP. We then propose a decision tree approach for cross-layer path selection that decides which path to carry the incoming packets dynamically according to the prior learned schemes. A prototype of the path selection system named SmartPS, which proactively probes the wireless environments, is realized and deployed in Linux and Android. Evaluation results demonstrate that our SmartPS can efficiently utilize the faster path, with goodput improvements of up to 29%.

中文翻译：

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移动设备多路径传输协议中的跨层路径选择

MPTCP 是一种新的传输协议，它使移动设备能够通过多个网络接口（例如 WiFi 和蜂窝网络）同时使用多个物理路径。然而，无线路径容量在移动环境中频繁变化，给路径选择带来了挑战。例如，当设备走开时，WiFi 相关路径通常会变差，因为 WiFi 具有由短信号覆盖和随机干扰引起的间歇性连接。MPTCP 基于滞后 TCP 层估计的本机决策将错过无线质量的真正切换点，这可能会在损坏的路径上累积数据包并导致严重的数据包重新注入。通过在野外分析一个独特的数据集，我们定量研究了 MAC 层因素对 MPTCP 聚合性能的影响。然后，我们提出了一种用于跨层路径选择的决策树方法，该方法根据先前学习的方案动态决定哪条路径携带传入的数据包。在Linux和Android上实现并部署了一个名为SmartPS的路径选择系统原型，它主动探测无线环境。评估结果表明，我们的 SmartPS 可以有效利用更快的路径，吞吐量提高高达 29%。