wCompound: Enhancing Performance of Multipath Transmission in High-speed and Long Distance Networks

As the user demand for data transmission over high-speed and long distance (hereafter abbreviated as HSLD) networks increases significantly, multipath TCP (MPTCP) shows a great potential to further improve the utilization of HSLD network resources than traditional TCP, and provides better quality of service (QoS). It has been reported that TCP causes serious waste of bandwidth in HSLD networks, while MPTCP can transmit data by using multiple network paths simultaneously between two distant hosts, thus provides better resource utilization, higher throughput and smoother failure recovery for applications. However, the existing multipath congestion control algorithms cannot perfectly meet the efficiency requirements of HSLD network, since they mainly emphasize fairness rather than other critical indicators of QoS such as throughput, but still encounter fairness issues when coexist with various TCP variants. To solve these problems, we develop weighted Compound (wCompound), a loss-and-delay-based compound multipath congestion control algorithm which is originated from Compound TCP, and is applicable to HSLD networks. Different from the traditional methods of setting an empirical value as the threshold, wCompound innovatively adopts a dynamic threshold and have the flexibility to adjust the sending window of each subflow based on current network state, so as to effectively couple all subflows and fully utilize the network capacity. Moreover, with the cooperation of delay-based and loss-based methods, wCompound also ensures good fairness to different types of TCP variants. We implement wCompound in the Linux kernel, then carry out sufficient experiments on our testbed. The results show that wCompound achieves higher utilization of network resources and can always maintain an appropriate throughput no matter competing with loss-based or delay-based network traffic.