A definition of overall telecommunication network performance is presented. A model of overall virtual telecommunication network (VNET), with QoS guaranties for Class 0 traffic (Real-time, jitter sensitive, high interaction: VoIP, Video Teleconference), is considered in stationary state, taking into account details of the users' behaviour. The approach described allows reducing the number of system describing parameters from over 260 (System Tuple) to 9 parameters: 8 static and one dynamic. This Minimal Tuple set and the correspondent equations described look as the minimal possible information for the overall telecom network performance modelling. The system of 9 equations presented, allows easy finding the all, important for overall network dimensioning/re-dimensioning, dynamic parameters.