Design of Folded/Unfolded Clos Networks for Data Centers with Extended Stages Guaranteeing Admissible Blocking Probability

Data center networks facilitate large-scale data processing by interconnecting multiple switching devices. Optical circuit switching (OCS) provides high transmission capacity and energy efficiency. It establishes dedicated paths for data transfer, ensuring reliable communication. A Clos network is widely used among multi-stage switching architectures due to its scalability and structured design. This paper investigates models for designing folded/unfolded Clos networks with an admissible blocking probability to maximize OCS network size. While previous studies have examined fundamental and stage-extended Clos networks, they have not addressed unfolded Clos network structures that maintain an admissible blocking probability across different configurations. To fill this gap, we introduce unfolded Clos network structures that ensure an admissible blocking probability for both fundamental and extended stages. We also discuss connection admission control mechanisms tailored to these network models. A key focus of this study is a comprehensive performance evaluation, including switching network size and computation time. Furthermore, we explore an alternative approach employing multiple network planes to enhance scalability and flexibility. The findings provide valuable insights into the design of large-scale OCS networks with controlled blocking probabilities.