We present an SDN-based orchestration system that enables automated and coordinated arrangement of both computing and network resources in virtualized DC environments. The orchestrator is validated through a set of simulations, as well as through experiments carried out in a real laboratory. Results show that the proposed orchestration system improves the service requests acceptance rate and the utilization of network resources, while minimizing degradations of the user experience. Thus, DC resources can be effectively exploited, and different management objectives (e.g., load balancing, energy saving) can be reached.