Multicast Scheduling for Optical Data Center Switches with Tunability Constraints

Optical multicasting based on passive star couplers and fast tunable transceivers is an attractive solution for the throughput and latency requirements of many data center applications. The limited tuning range of transceivers, however, may not be sufficient enough to enable the flexible scheduling of traffic. In this paper, we propose a suite of scalable scheduling algorithms for opticalmulticast switches with wavelength tunability constraints, considering both tunable and nontunable transmitters. To support scalability and scheduling fairness, we adopt a round-robin arbitration policy in conjunction with appropriate provisions to minimize the number of packet retransmissions. We conduct Monte Carlo simulations to compare the proposed algorithms. For 64 ports, 16 channels, and bursty multicast traffic, a scheduling that exploits transmitter tunability with minimal fan-out splitting can improve the maximum throughput by up to 60% compared to a fixed transmitter scenario.