Multirate Clos networks

Clos networks are a class of multistage switching network topologies that provide alternate paths between inputs and outputs, making it possible to minimize or eliminate the blocking that can otherwise occur in such networks. In his seminal paper in the Bell System Technical Journal in 1953, Charles Clos showed how these networks could be configured to make them nonblocking and effectively launched the systematic study of switching system performance, a field that has developed a rich technical literature, and continues to be very active and of continuing practical importance. This article describes how Clos' results have been generalized to systems that support connections with varying bandwidth requirements. These generalizations have extended the application of Clos networks well beyond their original technological context and have led to a number of interesting new results, especially in connection with systems that support multicast communication.