Performance evaluation of hybrid optical switch architecture for data center networks

Abstract

In response to the need for high bandwidth and power efficient data center interconnection networks, different interconnects have been proposed based on the optical technology used: micro-electromechanical system (MEMS), optical cross connects (OXCs), arrayed waveguide grating routers (AWGRs) and semiconductor optical amplifier (SOAs). MEMS switches are based on mature technology, have low insertion loss and cross-talk, and are data rate independent. They are also the most scalable and the cheapest class of optical switches. However, the reconfiguration time of these switches is of the order of tens of milliseconds while fast optical switches have switching time in the range of a few nanoseconds. Fast optical switches can be based on AWGRs in conjunction with tunable wavelength converters or tunable lasers or they are based on SOAs in broadcast-and-select architecture. In this paper, we propose an optical interconnect architecture for the large scale data centers. The proposed interconnect: Hybrid Optical Switch Architecture (HOSA) is a hybrid design that features slow and fast optical switches. The hybrid design leverages strengths of both types of optical switches. To reduce complexity, we employ a single stage core topology that can be easily scaled up (in capacity) and scaled out (in the number of racks) without requiring major re-cabling and network reconfiguration. We investigate the scalability of the HOSA and show that by using a single stage core topology, it can be scaled to a hundreds of thousands of servers. We also investigate a trade-off between cost and power consumption of our design by comparing it with other well-known interconnects by using analytical modelling. We demonstrate power efficiency as compared to other conventional interconnects on account of upfront CAPEX but the additional CAPEX incurred in deploying our solution instead of traditional architecture is mitigated to some extent by reduced OPEX, due to its greater energy efficiency. We evaluate the performance of the system using network-level simulation by considering diverse workload communication patterns and system design parameters. Our results show low latency and high throughput with different workload communication patterns.