Multipath TCP Scheduling in the Age of Buffer Bloat Optimizations

While several sophisticated scheduling strategies have been proposed to enhance performance of the Multipath Transport Control Protocol (MPTCP), most schedulers were implemented and evaluated before butter bloat optimizations have been introduced to the underlying Transport Control Protocol (TCP). Thus, the research question arises how these optimizations impact MPTCP performance across different scheduling strategies, and if a kernel-upgrade yields better results than changing the scheduler. To answer this question, we have upgraded several popular schedulers to the newer Linux kernel version 4, and conducted testbed measurements for different path rates and delays. Our data verifies that MPTCP indeed strongly benefits from the inherent TCP optimizations, so that the kernel upgrade often has a larger impact than a scheduler change. Thus, our findings indicate that the field of MPTCP scheduling must be revisited in the age of butter bloat optimizations.