3GPP 23.501 v20.2.0 — the document's own text
5.16.4.5 SMF and UPF selection function for Emergency Services
Taught in 21. Emergency calls, messages, voice and location (The 5G system architecture, in depth).
When a SMF is selected for Emergency Services, the SMF selection function described in clause 6.3.2 for normal services is applied to the Emergency DNN or the AMF selects the SMF directly from the AMF Emergency Configuration Data. If the SMF selection function described in clause 6.3.2 is used it shall always derive a SMF in the Serving PLMN or SNPN, which guarantees that the IP address is also allocated by the Serving PLMN or SNPN. When a UPF is selected for Emergency Services, the UPF selection function described in clause 6.3.3 for normal services is applied to the Emergency DNN or the SMF selects the UPF directly from the SMF Emergency Configuration Data. The information in the AMF Emergency Configuration Data and the SMF Emergency Configuration Data is specified in clause 5.16.4.1.