A Programming Model for Application-defined Multipath TCP Scheduling

Multipath TCP enables remarkable optimizations for throughput, load balancing, and mobility in today's networks. The design space of Multipath TCP scheduling, i.e., the application-aware mapping of packets to paths, is largely unexplored due to its inherent complexity. Evidence in this paper suggests that an application-aware scheduling decision, if leveraged right, pushes Multipath TCP beyond throughput optimization and thereby provides benefits for a wide range of applications. This paper introduces a high-level programming model that enables application-defined Multipath TCP scheduling. We provide an efficient interpreter and eBPF-based runtime environment for the Linux Kernel, enabling isolated application-defined schedulers in multi-tenancy environments. In combination with a high-level API, our work closes the gap between scheduler specification and deployment. We show the strength of our programming model by implementing seven novel schedulers tackling diverse objectives. Our real world measurements, for example, of an application- and preference-aware scheduler, show that the programming model enables timely scheduling decisions to retain fine-grained throughput objectives. Further measurements of a novel HTTP/2-aware scheduler show significantly improved interactions with upperlayer protocols, e.g., an optimized dependency resolution, while preserving path preferences.