IoDS: A Novel MPTCP Scheduler for Heterogeneous Networks

MPTCP, a TCP extension, provides the feasibility of using more than one network on the same connection to aggregate available bandwidth to increase the delivered data rate. However, MPTCP lacks a suitable universal scheduler that can perform efficiently in various scenarios to attain the mentioned goals. The reason is that MPTCP schedulers suffer from deficient mechanisms in scheduling the data into the available networks, resulting in issues such as out-of-order packet delivery or head-of-line blocking. This deficiency can be further exacerbated in heterogeneous networks due to the large differences in their characteristics, such as round-trip time dissimilarities. In this paper, we present a novel scheduler for MPTCP called In-order Delivery Scheduler (IoDS), which attempts to solve MPTCP issues in heterogeneous networks. IoDS schedules packets based on having insight into the networks' current states, mainly RTT, to deliver as much in-order data as possible to mitigate the number of out-of-order packets and head-of-line blocking problems. Extensive real-world experiments showed that the new scheduler outperformed all existing Linux kernel schedulers in most scenarios and improved user experience by reducing download time by up to 27 seconds, lowering standard deviation by over 71%, and ensuring uninterrupted 4K video playback in real-world conditions.