  Many optical circuit switched data center networks (DCN) have been proposed
in the past to attain higher capacity and topology reconfigurability, though
commercial adoption of these architectures have been minimal. One major
challenge these architectures face is the difficulty of handling uncertain
traffic demands using commercial optical circuit switches (OCS) with high
switching latency. Prior works have generally focused on developing
fast-switching OCS prototypes to quickly react to traffic changes through
frequent reconfigurations. This approach, however, adds tremendous complexity
to the control plane, and raises the barrier for commercial adoption of optical
circuit switched data center networks.
  We propose COUDER, a robust topology and routing optimization framework for
reconfigurable optical circuit switched data centers. COUDER optimizes topology
and routing based on a convex set of traffic matrices, and offers strict
throughput guarantees for any future traffic matrices bounded by the convex
set. For the bursty traffic demands that are unbounded by the convex set, we
employ a desensitization technique to reduce performance hit. This enables
COUDER to generate topology and routing solutions capable of handling
unexpected traffic changes without relying on frequent topology
reconfigurations. Our extensive evaluations based on Facebook's production DCN
traces show that, even with daily reconfiguration, COUDER achieves about 20\%
higher throughput, and about 32\% lower average hop count compared to
cost-equivalent static topologies. Our work shows that adoption of
reconfigurable topologies in commercial DCNs is feasible even without fast
OCSs.
