Redesigning the Nonblocking Clos Network to Increase its Capacity

The Clos network has been studied for decades as a class of nonblocking switching networks. However, the structure is based on assumptions made at the time of its design, and the assumptions may not remain entirely valid. For instance, an optimal Clos network usually consists of non-square switches (numbers of input and output ports differ), though the switches available today are square ones. In addition, all paths have to be of the same length in Clos networks (presumably to simplify signal setting), but this assumption is no longer valid since signals can be dynamically established nowadays. This paper carefully identifies the implicit assumptions of the Clos network and redesigns it to increase its capacity. Although the conventional Clos network using square switches has to leave several ports unused to realize the nonblocking property, our network has almost no unused ports, which greatly increases network capacity. In addition, our network does not fix the path length and well utilizes shortcut connections if available. Comprehensive theoretical analyses show that our network has a larger capacity than the Clos network under most conditions. Numerical evaluations demonstrate that our network increases the capacity 15% on average and up to 50% at most.