This Recommendation specifies a way to coordinate existing and ongoing works on service function chaining in mobile network (specified in [IETF RFC7665][IETF RFC 8300] and [b-ONF TS-027]) by introducing a chain orchestrator as a new entity. NOTE - [b-3GPP TS23.203] is another well-known specification on service function chaining. The Recommendation also covers the case when relevant network functions are virtualized. The objective of this document is to describe the requirements, architecture, functional entities, reference points and information flows of service function chaining in mobile networks.