AMF to (R)AN: N2 Request (N2 SM information received from SMF, security context, AMF Signalling Connection ID, Handover Restriction List, Subscribed UE-AMBR, MM NAS Service Accept, list of recommended cells / TAs / NG-RAN node identifiers).
For UE in CM-CONNECTED state, if the Service Request procedure is triggered by UE, only N2 SM information received from SMF and MM NAS Service Accept are included in the N2 Request. If the Service Request procedure is triggered by the Network as described in clause 18.104.22.168
, only N2 SM information received from SMF is included in the N2 Request.
For UE in CM-IDLE state, RAN stores the Security Context, AMF Signalling Connection Id, QoS Information for the QoS Flows of the PDU Sessions that are activated and N3 Tunnel IDs in the UE RAN context. Handover Restriction List is described in TS 23.501  clause 22.214.171.124 "Mobility Restrictions"
MM NAS Service Accept includes PDU Session status in AMF. If the activation of UP of a PDU Session is rejected by an SMF, then the MM NAS Service Accept includes the PDU Session ID and the cause why the user plane resources were not activated (e.g. LADN not available). Any local PDU Session Release during the Session Request procedure is indicated to the UE via the Session Status.
If there are multiple PDU Sessions that involves multiple SMFs, AMF does not need to wait for responses from all SMFs in step 3 before it send N2 SM information to the UE. However, the AMF shall wait for all responses from the SMFs before it sends MM NAS Service Accept message to the UE.
AMF shall include at least one N2 SM information from SMF if this step is triggered for PDU Session User Plane activation. AMF may send additional N2 SM information from SMFs in separate N2 message(s) (e.g. N2 tunnel setup request), if there is any. Alternatively, if multiple SMFs are involved, the AMF may send one N2 Request message to (R)AN after all the Nsmf_PDUSession_UpdateSMContext Response service operations from all the SMFs associated with the UE are received. In such case, the N2 Request message includes the N2 SM information received in each of the Nsmf_PDUSession_UpdateSMContext Response and PDU Session ID to enable AMF to associate responses to relevant SMF.
If the NG-RAN node had provided the list of recommended cells / TAs / NG-RAN node identifiers during the AN Release procedure (see clause 4.2.6
), the AMF shall include it in the N2 Request. The RAN may use this information to allocate the RAN Notification Area when the RAN decides to enable RRC Inactive state for the UE.
The AMF based on network configuration, may include the UE's "RRC Inactive Assistance Information" as defined in TS 23.501