User Network Interface
In the field of telecommunications, the User Network Interface acts like a demarcation point between the subscriber’s responsibility and service provider’s responsibility. The User Network Interface is distinctly different from the Network to Network Interface or NNI which may be a similar interface but between provider networks. So the UNI refers to the interface point between a private ATM switch and ATM end users or between a private ATM switch and public carrier ATM networks.
The User Network Interface is physically set up across a bi-directional ETH link which offers the data and management power needed by the MEN service provider in order to clearly differentiate the two network domains that are engaged in the administrative, operational, provisioning aspects and maintenance of the service. So, the UNI defines the physical and protocol interface specifications for the devices which are linked at the edge of the ATM networks. This will therefore include all systems which are linked to a private ATM switch or connections between such a private ATM switch and public carrier owned ATM switch. Another significant ATM interface is the Network to Network Interface or NNI that refers to interface between switches in a backbone network. The UNI lets end systems establish SVCs across switches while the NNI automatically builds full mesh PVC connections.