Evolution of 4ESS(TM) Field Support

Since the initial deployment of the 4ESS(TM) in Chicago in 1976, a great many changes have been made not only to its software and hardware, but also its role in the AT&T long distance network. Earlier services and capabilities were largely implemented on the 4ESS(TM) itself with interfaces to various Operating Support Systems (OSSs). Advances in technology have created a more distributed architecture in which network services are implemented across several machines and data bases.