In this paper, we describe a framework for designing a discrete-bandwidth nonblocking network. The theoretical foundation of the framework combines theories from both networking and switching. While the conventional Clos theory must assume a particular topology, the new theory allows us to design a nonblocking network with an arbitrary topology. Thus it can be considered as a generalization of the Clos theory. In addition to the design of WDM or SONET networks, applications such as grid computing and supercomputing can also benefit from the results developed in the paper.