Section 9.1: Integrating the Public Switched Telephone Network

Asynchronous Transfer Mode (ATM) standards are referred to as Broadband ISDN (BISDN) in the International Telecommunication Union (ITU) standards publications. BISDN is the next evolution of ISDN, providing higher bandwidth and faster speeds than ISDN. The ATM Forum has gone one step further and defined services for non-BISDN applications (data only). These applications are data-specific, and include applications such as bridging Local Area Networks (LANs) through ATM connections. BISDN standards define integration of data, video, and voice networks over one network.

Integration is certainly not a new concept. The whole basis of ISDN was to create one common interface to support all forms of traffic, including data and video. ISDN fell short of delivering for a variety of reasons, and its acceptance has been slow because of a lack of killer applications.

ATM has already suffered some of the same maladies as ISDN. Slick marketing has touted ATM as the network solution, providing more bandwidth to the desktop than anyone could possibly need. Which was exactly the problem. Very few companies have expressed a need, let alone an interest, in having more than 100-Mbps bandwidth delivered to their desktops.

So why was ATM developed? The original idea was fostered by the Bell Operating Companies (BOCs) long before divestiture. The idea of integrating their telephone networks generated the idea of ATM to replace the existing circuit-switched network. ISDN was the first step in integration, but as time evolved, the telephone companies recognized the...