Omniscient TCP for congestion control in data centre networks
25 April 2016
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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.