Service providers typically operate large and complex multi-layer/multi-vendor networks based on IP/Optical systems in which the different technological layers are seldom jointly managed. In this context, a logically centralized component, called network orchestrator, can help to achieve dynamic control, planning and optimization for optimal service accommodation, according to both the availability of resources and the needs of the applications. The presentation will provide insight to the relevant work taking place in the EC-funded research and innovation project ACINO, which is investigating the introduction of the application-centric concept in multi-layer IP/Optical networks. By means of its network orchestration solution, ACINO aims at differentiating the service offered to each application at each layer of the transport network. The proposed concept has been already demonstrated over a real IP/optical testbed with two relevant use-cases for network operators: policy-based reactive failure recovery and secure transmission as a service.