Progress on broadband ISDN user-network interface standards

The author reports on the current definition of the B-ISDN (broadband integrated services digital network) user-network interface (UNI). The UNI reference configuration, physical medium, rates, structure, ATM (asynchronous transfer mode) functions, and operations and maintenance functions are addressed with consideration given to open issues and the direction of future standards activities. Objectives for the UNI capabilities have generally been met with the current CCITT specifications. Some of the UNI physical layer options, however, potentially impose networking cost penalties. It is concluded that in future standards work it will be desirable to limit the scope of these options and minimize any additional options which only result in increased networking (and therefore service) costs