Testing Multipath TCP and Congestion Controls on the Linux 6.8 Kernel in a Proxmox Virtual Environment

Abstract

This thesis investigates the performance of Multipath TCP (MPTCP) in Linux Kernel 6.8 using a low-cost Proxmox virtual environment. Key findings reveal that MPTCP in Linux Kernel 6.8 is significantly influenced by single-path congestion control configurations, allowing for better optimization for wireless networks than expected from specifications in RFC 8685. The research identifies optimal congestion control settings for MPTCP in a simulated 5G and Wi-Fi 6 environment: BBR and BIC for maximizing bandwidth, Westwood+ for ensuring fairness, and Vegas for low-priority, low-latency flows. While MPTCP achieved 1.125-1.4 times more bandwidth than a competing single-path TCP flow, it maintained high fairness as measured by Jain’s Fairness Index. Additionally, the study finds that TCP-LP, designed for low-priority traffic, is dysfunctional in Linux Kernel 6.8, indicating a need for kernel updates. These findings provide actionable guidance to system administrators and application developers seeking to optimize network utilization, particularly for mobile devices with dual connectivity. Moreover, they have implications for emerging protocols like QUIC and MPQUIC, which share similar congestion control mechanisms with TCP and MPTCP, and the future of the HTTP/3 internet.