Pipelining multicast scheduling in all-optical packet switches with delay guarantee

In this paper, we study multicast scheduling in all-optical packet switches. First, we 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 also discuss some desirable features of DGMS in detail, such as guaranteed delay upper bound and adaptivity to transmission requirements. To relax the time constraint of DGMS, we further propose a pipelining technique that distributes the scheduling tasks among a sequence of sub-schedulers. The combinatorial logic circuit design of each sub-scheduler, which further reduces time complexity, is also provided. 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.