6 Roles for registration in the IM CN subsystem for service continuity

24.3373GPPIP Multimedia (IM) Core Network (CN) subsystem IP Multimedia Subsystem (IMS) inter-UE transferRelease 17Stage 3TS

6.1 SC UE

The SC UE shall follow the procedures specified in 3GPP TS 24.229 [7] for registration of the UE in the IM CN subsystem.

If the SC UE supports the Controller UE procedures for IUT transfer then the SC UE shall include the g.3gpp.iut-controller media feature tag as described in annex B in the Contact header field of the SIP REGISTER request.

6.2 SCC AS

The SCC AS can obtain registration state information that it needs to implement SCC specific requirements from:

a) any received third-party SIP REGISTER request (e.g. including information contained in the body of the third-party SIP REGISTER request) as specified in 3GPP TS 24.229 [7];

b) any received reg event package as specified in 3GPP TS 24.229 [7]; or

c) the Sh interface as specified in 3GPP TS 29.328 [26] and 3GPP TS 29.329 [27].

NOTE: Obtaining registration state information from HSS using Sh interface does not allow the SCC AS to know the capabilities supported by the user registered UE(s), including the used IP-CAN(s).