This document proposes a new modeling language called Network Modeling Language (NML) to model software-defined networking (SDN) and automatically generate simulations using different performance models like queueing Petri nets (QPN) and stochastic Petri nets (SPN). It presents the NML metamodel and model transformations from NML to QPN and SPN. Experiments comparing the accuracy and simulation time of the generated QPN and SPN models against real measurements on a SDN testbed show that QPN predictions have 3% error while SPN simulations are faster but less accurate. The work contributes an approach for automatic performance prediction of SDN networks from a single high-level model.