ISDN standards evolution

The evolution of the Integrated Services Digital Network (ISDN) from a primarily analog telephony network includes the evolution of standards that define the ISDN framework and services, as well as signaling and management functions. The International Telegraph and Telephone Consultative Committee (CCITT) has already defined many of the necessary standards. For example, circuit-switched, packet-switched, and private-line capabilities have been standardized, as well as two types of interfaces to connect customer premises equipment to the network. Standards need to be extended to cover, for instance, the integration of video into the ISDN framework, including the definition of a new wideband customer interface. New technologies such as wideband packet and fiber also need to be considered. This article describes the existing ISDN standards and presents an evolutionary scenario for future standards.