A mobility service and control function (MSCF), operating in an application layer of a wireless transmit/receive unit (WTRU), selects and controls a plurality of mobility services. These mobility services may include session initiation protocol (SIP), Internet protocol (IP) Multimedia subsystem (IMS), voice call continuity (VCC), mobile IP (MIP), proxy MIP (PMIP), and generic access network (GAN), but are not limited thereto. The MSCF further selects and controls a plurality of air interface technologies for accessing a plurality of radio access networks. The MSCF allows application layer handling of mobility management.