Switching systems in the 21st century

The historical forces that have shaped the current structure of telephone switching systems and how telecommunication engineers think about switching systems are discussed. The ways in which the new service-driven forces will change the switching system structures and how they are viewed are examined. It is argued that the general trend toward more and more telecommunication services with faster and faster deployment schedules is leading toward the second big separation of central control within switching systems. The first was the centralization of connectivity control within each switch early in the century, and the second is the separation of the services provided from the associated connectivity actions required to provide the services. One of the primary differences between the two separations is that the first favored leaving the results of the division on the switches, while the second separation permits the services to be provided by systems on or off the basic interconnection machines.<>