  Hybrid switching - in which a high bandwidth circuit switch (optical or
wireless) is used in conjunction with a low bandwidth packet switch - is a
promising alternative to interconnect servers in today's large scale
data-centers. Circuit switches offer a very high link rate, but incur a
non-trivial reconfiguration delay which makes their scheduling challenging. In
this paper, we demonstrate a lightweight, simple and nearly-optimal scheduling
algorithm that trades-off configuration costs with the benefits of
reconfiguration that match the traffic demands. The algorithm has strong
connections to submodular optimization, has performance at least half that of
the optimal schedule and strictly outperforms state of the art in a variety of
traffic demand settings. These ideas naturally generalize: we see that indirect
routing leads to exponential connectivity; this is another phenomenon of the
power of multi hop routing, distinct from the well-known load balancing
effects.
