Many legacy systems are still essential. They run efficiently and accurately in legacy hardware and software environments. Therefore, it is necessary to migrate legacy hardware and software to modern platforms. One of the directions of migration is to service-oriented architectures. In this case, side effects are possible. Therefore, it is necessary to use the software system model. This model is used to assess the migration process of legacy software systems. An approach for building network models from the ground up is proposed in this research. Time-dependent Petri nets are used to explain the traces of events in the simulated network. A user may create a network workload model that can be utilized for network planning purposes using this technique. A method must be established to determine whether or not the created model is suitable. An example is used to determine the suitability of the Markov model for the behavior of a system with discrete states in terms of precision. An example is used to build a model for the operation of a basic software system. Providing the executable network model of the migrating system to the service identification approach input is preferred.