16 Messaging service

15 Presence service

14 Interoperability of IMS Service Continuity over II-NNI

10 Security

13 Interoperability of IMS Centralized Services (ICS) over II-NNI

11 Charging

12 Supplementary services associated with the IMS multimedia telephony communication service

6 Control plane interconnection

9 IP Version

8 Numbering, Naming and Addressing