Performance monitoring of digital networks

The author examines the evolution of digital network performance monitoring capabilities from the early point-to-point single DSI circuits used internally by the operating telcos, through today´s advanced ESF (Extended Superframe) techniques and projects, and ahead to the rapidly approaching FT1, DS3, ISDN, and SONET capabilities. It is pointed out that, although T1 circuits were initially installed with minimal performance monitoring capability, particularly for the end users, these are being upgraded to the current ANSI ESF, which does an adequate job. The future network standards of ISDN primary rate access (PRA) and of SONET will have even better performance monitoring capabilities