  We study how to reduce the reconfiguration time in hybrid optical-electrical
Datacenter Networks (DCNs). With a layer of Optical Circuit Switches (OCSes),
hybrid optical-electrical DCNs can reconfigure its logical topologies to better
match the on-going traffic patterns, but the reconfiguration time may directly
affect the benefits of reconfigurability. The reconfiguration time consists of
the topology solver running time and the network convergence time after
triggering reconfiguration. However, existing topology solvers either incur
high algorithmic complexity or fail to minimize the reconfiguration overhead.
  In this paper, we propose a novel algorithm that combines the ideas of
bipartition and Minimum Cost Flow (MCF) to reduce the overall reconfiguration
time. For the first time, we formulate the topology solving problem as a MCF
problem with piecewise-linear cost, which strikes a better balance between
solver complexity and solution optimality. Our evaluation shows that our
algorithm can significantly reduce the network convergence time while consuming
less topology solver running time, making its overall performance superior to
existing algorithms. Our code and test cases are available at a public
repository.
