Parallel Distributed Schedulers for Scalable Photonic Integrated Packet Switching

As data centre traffic dynamics are changing, optical networking is becoming increasingly important for low-latency, high bandwidth intra-data centre communication. Nanosecond-reconfigurable, scalable photonic switch fabrics and advances in photonic integration are key enablers for optical packet switching. However, the control plane and in particular the switch scheduler is believed to be a critical factor on packet latency and scalability. To that end, we report a low-latency scheduler for Clos-network switch fabrics based on a fixed path assignment scheme and parallel and distributed path arbitration. Cycle-accurate network emulation results show nanosecond average latency at input port loads up to 60% of capacity for a 256×256 switch size. In comparison to previous work, the scheduler can now control a switch 8 times the size at double the input port saturation load for the same average latency. Scaling the switch from 16 to 256 ports shows only a small drop in saturation load from 70% to 60%. Also fairness on a per flow basis is demonstrated.