ISDN Elements and Architecture

Abstract

In retrospect, integrated services digital network (ISDN) was initiated in November 1986. The ISDN trials started in earnest in 1987. By late 1988, US WEST, one of the Regional Bell Operating Companies (RBOCs), was offering basic and primary rate ISDN services on an individual trial basis. Basic rate (2B+D) services and bearer channel transparency were demonstrated during the 1990 international ISDN trials between the United States and Japan. By the end of 1992, US WEST had about 1,500 basic rate ISDN (BRISDN) and 70 primary rate ISDN (PRISDN) customers. During late 1992, an effort to establish nationwide ISDN (sometimes referred to as ISDN-1) was in place, which had the ability to interconnect the major ISDN switches distributed around the United States and Canada. The national ISDN-2 and ISDN-3 networks offered solutions to address services for telecommuting, videoconferencing, multipoint screen-sharing applications, image communications, customer call handling, ISDN workstations, ISDN access to LANs, highspeed file exchange, document storage retrieval, transparency between ISDN and private branch exchange (PBX) applications, frame relay support, and centralized ISDN-based FAX facilities. It is expected that the ISDN-3 services (listed above) will become a reality by the late 1990s.