A Review of CCITT Standardization to Date

This paper describes the key elements of the International Telephone and Telegraph Consultative Committee´s (CCITT´s) three Recommendations on ISDN services. Telecommunication services which can be offered to customers are the natural starting point for all standardization work on telecommunication networks. The necessary features of telecommunication networks can only be derived from the services´ requirements. The early standardization of services has the added advantage that it allows communication across borders to be made available on identical terms. For the reasons given here, the CCITT has, in all its work on ISDN, given a high priority to a uniform definition of the services and to the specification of services to be offered internationally.