Optimal Configuration of High-Radix Combined Switches

High-radix switches are an attractive option to improve network performance and to reduce network cost, especially in large switch-based interconnection networks. However, there are some problems related to the integration scale to design such single-chip switches. In this paper we describe an interesting alternative for building high-radix switches which basically consists in combining several current smaller single-chip switches to obtain switches having greater number of ports. This approach is independent of the evolution of single-chip switches and will remain valid as integration scale keeps evolving. We discuss about key design issues of this kind of switches and focus on their internal structure. In order to show the relevance of this issue, we obtain the optimal internal configuration of switches for several networks and evaluate the network performance considering different conditions. Simulation results show that with a correct internal switch design, a network based on these high-radix switches achieves similar performance to a network based on single-chip switches, which have the same number of ports as high-radix switches, and which would be unfeasible with the current integration scale.