Understanding Delayed Reaction of MPTCP Scheduler Over 5G for Realtime Applications

The advent of 5G networks promises to revolutionize real-time applications with its high bandwidth capabilities. Despite this, current real-time applications such as 360-degree video conferencing and intelligent transport systems, which demand high data rates and stringent low latency, often find it difficult to satisfy their QoS needs with a single 5 G connection due to inconsistent bandwidth. As a viable option, multipath transport solutions using multiple 5G connections have emerged with recent technological advancements. In this paper, we explore real-time application performance using MPTCP over 5G multiple connections. Our real-world measurements over MPTCP across major 5G operators in South Korea reveal average frame delays exceeding 213 ms. This delay is much higher than our expectations compared to measurements over single-path TCP (SPTCP) under similar network conditions. We attribute this to the delayed reaction of the MPTCP scheduler, which relies on long-term measurements rather than adapting to recent network conditions. The delayed reaction causes sub-optimal path selection and increased latency. This paper contributes a thorough analysis of MPTCP performance degradation in real-time applications, identifies the limitations of current MPTCP schedulers, and considers potential solutions to improve their responsiveness to achieve better application latency performance.