Evaluation of Packet Schedulers for Multipath QUIC

Abstract: The Web has outgrown the transport mechanisms that have been used since its inception. Due to the increasing complexity of web pages in terms of both total size and number of individual resources, HTTP over TCP can no longer provide a satisfactory user performance. In recent years, much progress has been made in this area by evolving the web's underlying mechanisms. Multipath QUIC (MPQUIC) is one such approach. MPQUIC is a new transport protocol which enables multihomed devices, such as smartphones, to aggregate their network interfaces in order to achieve greater performance. Additionally, MPQUIC is capable of multiplexing several data streams concurrently over a single connection, which can also provide performance benefits. This work began with a validation of our MPQUIC setup, which was performed by comparing MPQUIC to another multipath solution in a large set of experiments. The results show that MPQUIC is generally beneficial for the transfer time of large files, which corresponds with results from previous works. We additionally investigated ways to exploit MPQUIC's multipath and stream features to achieve lower latencies for web pages via the means of packet scheduling. We implemented the Earliest Completion First (ECF) scheduler, and investigated how it compares against MPQUIC's default path scheduler. The results indicate that the ECF scheduler is significantly more capable of handling heterogeneous network scenarios than the default scheduler, and can achieve higher throughput and lower latencies. Next, a Stream Priority scheduler was designed and implemented, which utilizes stream priorities to achieve lower completion times for select streams. The results from the investigation indicate that proper stream scheduling can significantly reduce download times of the prioritized resources. This effect was especially noticeable as path characteristics diverge. We also show that proper configuration of stream priorities is critical for such a scheduler, as a sub-optimal configuration yielded poor performance.