user-network interface (UNI)
1. The point of demarcation between a common carrier’s facilities and customer’s installation, which demarcation establishes both the technical interface and the division of operational responsibility. In this context, “customer” refers to the end-user. [J. Beaty FAA]
2. The term used to refer to the network interface (NI) as well as to interfaces within the customer installation (CI). [T1.640-1996]