This Recommendation defines the functional architecture of software-defined networking (SDN) by describing a layered architecture@ the functional components of the architecture and its reference points. Details of multi-layer management are provided in Annex A and the role of orchestration is addressed in Appendix I. The architecture is based on [ITU-T Y.3300] which defines the SDN framework and [ITU-T Y.3301] which describes the functional requirements of the SDN architecture which the present Recommendation has to fulfil.