Section: 5.16.3.6 Terminating domain selection for IMS voice
Content: When requested by IMS, the UDM/HSS shall be able to query the serving AMF for T-ADS related information. T-ADS is a functionality located in the IMS and is performed as specified in TS 23.221[ Architectural requirements ]  [23]. The AMF shall respond to the query with the following information unless the UE is detached: - whether or not IMS voice over PS Session is supported in the registration area (s) where the UE is currently registered; - whether or not IMS voice over PS Session Supported Indication over non-3GPP access is supported in the WLAN where the UE is currently registered; - the time of the last radio contact with the UE; and - the current Access Type and RAT type.