In the year 2000 the telecommunication market entered a very deep recession. In the current marketplace the service providers must improve network management to reduce operation costs. ATM network service providers offered mainly permanent virtual circuit connections to customers in the last years, but recently there is an increasing interest to offer switched virtual circuit (SVC) connections to end users. The SVC is based on the use of signalling protocols. Our paper focuses on the performance of call processing in ATM networks. Based on a series of measurement results that have a wide generality among ATM switches, we have built up a node-model to design large ATM signalling networks. The paper shows that a cascaded network is a good estimator for the signalling performance of an arbitrary network. In addition, it is shown that the call density of the network is an important network parameter, which is closely related to the maximum networ-level call arrival rate. The case studies are extended from homogeneous networks to hybrid networks.