Influence of Congestion Control Algorithms on Head-of-Line Blocking in MPTCP-based Communication
Michał Morawski, Przemysław Ignaciuk · 2019
The computers manufactured today are equipped with multiple communication interfaces. However, they cannot be used simultaneously to transfer the data due to design restrictions of the primary networking protocols, especially TCP. Its legacy, single-flow versions allow for engaging only one interface at a time for a given application stream. Recently, this inopportune limitation has been relaxed by the standardization of a multipath version-MPTCP. Still though, only one type of congestion control algorithm is used to control the flow of data, despite multiple choices available in the modern operating systems, which leads to non-optimal transfer dynamics. In addition, the multipath connection, although deemed to achieve higher throughput, may arrive at inferior performance when the transmission at the individual paths is throttled, e.g., as a result of drops. This phenomenon-Head of Line (HoL) blocking - poses a serious challenge to wide adoption of MPTCP. In this work, the influence of popular TCP congestion control algorithms, operating at the path and MPTCP level, on HoL blocking phenomenon is examined experimentally. The investigated scenarios, involving a low-end client communicating via heterogeneous, public networks with a high performance data server, set the basis for recommendations about efficient congestion control algorithm selection in common network applications. The default algorithm configuration is found ill-suited in the majority of the considered cases, yielding priority to nonhomogeneous settings.