Multihop routing enabled packet switching with QoS guarantee in optical clos for data centers

High-performance scalable data centers call for huge-capacity optical packet switches and QoS (quality- of-service) guaranteed multistage switching, where reconfiguration overheads of optical fabrics and efficiency of scheduling algorithms are two key challenges. We consider QoS guaranteed scheduling for optical packet switching in Clos networks with optical crossbar fabrics, where spatial speedup can be implemented using multiple parallel- working middle-stage switches to fight against switch reconfiguration overhead. By following the existing traffic matrix decomposition approach, our focus is to improve scheduling efficiency by enabling multihop routing in the scheduling process. In particular, we propose a two-step DETOUR algorithm. The first step generates a schedule to achieve QoS guaranteed switching without packet loss and with a bounded packet delay. The second step finds possible multihop routes across a set of switch configurations that can be used to achieve better load-balancing and make use of the idle time slots/bandwidth for additional packet transmissions. This leads to higher scheduling efficiency, which further translates to lower average packet delay. Simulation results confirm the good performance of the proposed DETOUR algorithm.