WDM Recirculation Buffer-Based Optical Fabric for Scalable Cloud Computing

Optical packet switching is the next-generation disruptive technology for massive cloud data centers. All-optical routers, supporting wavelength parallelism, accelerate the execution of applications and facilitate server virtualization. Despite the recent advances in optical technologies, the greatest challenge in the realization of optical routers is the lack of a mature solution for buffering optical signals. Fiber delay lines (FDLs) have been proposed to emulate electronic buffering by delaying contending optical packets for a fixed amount of time. However, the practical limitation on the number of FDLs in a router requires its ports to be run at low utilization, sacrificing a significant portion of network capacity. In this paper, we introduce a novel modular router architecture based on wavelength-division multiplexed (WDM) recirculation buffers as a solution to the problem of limited buffering capacity. We propose a load-balancing scheduler to maximize throughput. Our mathematical analysis and Monte Carlo simulations show that the consolidation of optical buffers in WDM FDLs accompanied with internal load balancing leads to a virtually lossless router, resilient to data center traffic anomalies. The load balancing further minimizes the number of packet recirculations, leading to negligible queueing latency. Our design supports physical layer scalability and is amenable to large-scale optical integration.