Signal networks optimalization, methods of performance evaluation. Stochastic models in telecommunication networks, stochastic processes, discrete and continuous Markov's chain, Kendall's classification of queuing systems and characterization of basic queuing systems. Special types of queuing systems with losses, wating and priority. Multiphases queuing systems, closed and opened Jackson networks. System with Poisson and non-Poisson distribution of arrivals and with Erlang distribution of order r. Markov's models and their application in service center dimensioning, design of call center with front-end IVR and calculation of traffic parameters. Dimensioning and overload protection in intelligent networks. Basic rules of enterprise networks' design.