This Recommendation provides use cases and functional requirements of Network as a Service (NaaS)@ one of the representative cloud service categories. This Recommendation covers the following: ?C High-level concept of NaaS; ?C Functional requirements of NaaS; ?C Typical NaaS use cases. This Recommendation provides use cases and functional requirements of NaaS application@ NaaS platform and NaaS connectivity. NOTE ?C General requirements of NaaS can be found in [ITU-T Y.3501].