The most important development in the computer communication industry in 1990 is the evolution the integrated services digital network (ISDN) and its follow on, the broadband ISDN (B-ISDN). The ISDN and B-ISDN have had a dramatic impact on the planning and the deployment of intelligent digital networks providing integrated services for voice, data and video. Further, the work on the ISDN and B-ISDN standards has led to the development of two major technologies: frame relay and asynchronous transfer mode (ATM). Frame relay and ATM have become the essential ingredients in developing high speed networks for local, metropolitan, and wider area networks.