In the indirect and hybrid models, the deployment of a SCS may be inside or outside the operator domain as illustrated in Figure A-1 and Figure A-2. When the SCS is part of the operator domain (Figure A-1 C and Figure A-2), the SCS is considered a mobile operator internal network function, is operator controlled, and may provide operator value-added services. In this case, security and privacy protection for communication between the MTC-IWF and SCS is optional. When the SCS is deployed outside the operator domain (Figure A-1 B and Figure A-2), the SCS is MTC Service Provider controlled. In this case, security and privacy protection for communication between the MTC-IWF and SCS is needed. In the direct model (Figure A-1 A), there may not be an external or internal SCS in the communication path.

An operator may deploy the hybrid model with a combination of no internal and external SCS (as in the Direct Model) and internal and/or external SCS (as in the Indirect Model). As shown in Figure A-2, a UE may be in communications with multiple SCSs in an HPLMN which can be made up of a combination of operator controlled and MTC service provider controlled SCSs. In that scenario, the MTC Service provider controlled SCS, and the 3GPP operator controlled SCS may offer different capabilities to the MTC Applications. Though not illustrated, it is also possible that the deployment of an AS may be inside the operator domain and under operator control.