High-speed multicast scheduling for all-optical packet switches

In this paper, we study multicast scheduling in all-optical packet switches. We first propose a novel optical buffer called multicast-enabled Fiber-Delay-Lines (M-FDLs), which can provide flexible delay for copies of multicast packets using only a small number of FDL segments. We then present a Delay-Guaranteed Multicast Scheduling (DGMS) algorithm that considers the schedule of each arriving packet for multiple time slots. We show that DGMS has several desirable features, such as guaranteed delay upper bound and adaptivity to transmission requirements. To relax the time constraint of DGMS, we further propose a parallel and pipeline architecture for DGMS that distributes the scheduling task to multiple pipelined processing stages, with N processors in each stage, where N is the switch size. Finally, by using a simple combination logic circuit, we show that each processor can finish the scheduling for one time slot in O(1) time. The performance of DGMS is tested extensively against statistical traffic models and real Internet traffic, and the results show that the proposed DGMS algorithm can achieve ultra-low average packet delay with minimum packet drop ratio.