Nonblocking, repackable, and rearrangeable Clos networks: fifty years of the theory evolution

The article gives an overview of major theoretical issues associated with a switching network structure proposed by C. Clos (1953). The concepts of strict-sense and wide-sense nonblocking as well as repackable and rearrangeable networks are described, showing the development of major research areas. A taxonomy of Clos switching networks and some important results for the basic network structure are given and discussed. Other research issues are enumerated.