4.23.2 I-SMF selection

23.5023GPPProcedures for the 5G System (5GS)Release 18TS

For non-roaming or LBO roaming case, the AMF selects an SMF serving the PDU Session as described in clause 4.3.2.2.3. If the service area of the selected SMF does not control UPF that can serve the UE location, the AMF selects an I-SMF as described in clause 5.34.3 of TS 23.501 [2].

After the PDU Session is established, if the selected SMF cannot serve the target DNAI requested by the PCC rule, the SMF issues Nsmf_PDUSession_SMContextStatusNotify to provide the target DNAI information to the AMF. Then AMF selects an I-SMF that serves this target DNAI as described in clause 5.34.3 of TS 23.501 [2].

For home routed roaming case, the AMF selects V-SMF as described in clause 4.3.2.2.3.2 and reselects V-SMF as described in clause 5.34.3 of TS 23.501 [2].

When the delegated discovery is used, the SCP selects the SMF as described in clause 5.34.3 of TS 23.501 [2] and in Annex E.