This Recommendation identifies network and terminal functions that are specific for the support of IMT-2000 services, as specified in the Recommendation on the Framework for IMT-2000 Networks (Recommendation Q.1701). These functions together with other, more conventional network functions are then grouped into functional entities in a generic functional model. In the functional model, the relationships among functional entities and groups are shown. The functional model is mapped onto a generic network reference model to illustrate possible groupings of functional entities into physical collections of entities. Based on the functional model, global roaming requirements and network interconnection scenarios are described. This Recommendation forms the basis for the development of information flows and the definition of functional entity actions and the development of signalling requirements for the various interfaces identified in Recommendation Q.1701.