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Omniscient TCP for congestion control in data centre networks

25 April 2016 / cc

Simon Jouet presented his work on OTCP: SDN-Managed Congestion Control for Data Centre Networks at the IEEE/IFIP Network Operations and Management Symposium workshop in Istanbul, Turkey, in April 2016. OTCP is an OpenFlow-based approach to tuning TCP congestion control parameters to better match network characteristics that can improve flow completion times in data centre networks.

The latency and throughput of data centre networks differs significantly from that of wide-area Internet paths. This causes problems when using TCP, since operating systems tend to make conservative choices for the congestion control parameters, that suit wide-area paths but not data centres. Accordingly, TCP achieves poor performance, potentially even overloading the network due to in-cast collapse.

To address this, Omniscient TCP uses software-defined networking tools to estimate the correct TCP parameters, and tunes the congestion control to the data centre environment. Specifically, it uses OpenFlow to measure path latency, throughput, and switch buffering, then this information to tune the TCP retransmission timers, and the initial and maximum congestion window, to match the network. Evaluation on Mininet shows that this can significantly reduce flow completion times at the mean and 95th percentile, as well as improving fairness and reducing end-to-end delay.