scope:

The present document describes the extensions required for the support of Virtual Private Network (VPN) applications over the public Network Nodal Interface (NNI). This application makes use of the Application Transport Mechanism described in Q.apm for bearer-related signalling, and the Transaction Capability for signalling involving no bearer. The present document specifies the respective users (i.e. APM-user, TC-user) to support the PSS1 information flows continuity in VPN applications. The public NNI provides transparency to the services of the private network.

The private network functionality is defined by ISO in its series of standards for Private Integrated Services Network. In addition, the concept of a "Relay node" is introduced by the present document.