(User-to-Network Interface) UNI is a standard developed by the ATM Forum to provide specifications for procedures and protocols used to connect ATM network switches to end-stations (The Frame Relay Forum has developed a UNI for connecting users to Frame Relay networks )
(user-to-network interface) The reference point where the protocols for compatibility between customer premises equipment (CPE) and a carrier network must be defined A UNI specification defines in detail the Layer 1 and Layer 2 and perhaps Layer 3 protocols that are required for CPE and carrier equipment to interoperate
User-Network Interface: An interface point between ATM end users and a private ATM switch, or between a private ATM switch and the public carrier ATM network; defined by physical and protocol specifications per ATM Forum UNI documents The standard adopted by the ATM Forum to define connections between users or end stations and a local switch