Section: 4.11.4.2 Handover from 5GS to EPC/ePDG
Content: Figure 4.11.4.2-1: Handover from 5GS to EPC/ePDG NOTE: In step 2, the UE can also trigger this procedure when 5G NAS (i.e. N1 mode) capability is disabled while the UE is in 5GS. 0. Initial status: one or more PDU Sessions have been established between the UE and the SMF/UPF via NG-RAN. 1. The UE connects to an untrusted non-3GPP access and the N3IWF-ePDG selection process results in selecting an ePDG. 2. The UE initiates a Handover procedure as described in clause 8.6.2.1 of TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [26], except step 11 of referenced figure 8.2.3-1 that corresponds to the release of resources in source system. 3. The combined PGW+SMF/UPF initiates a network requested PDU Session Release via 3GPP access according to Figure 4.3.4.2-1 steps 3b to 7b, step 11 or Figure 4.3.4.3-1 steps 3a-16b to release the 5GC and NG-RAN resources with the following exception: - For non-roaming or local breakout in clause 4.3.4.2, the SMF does not include N1 SM Container in Namf_Communication_N1N2MessageTransfer service operation. - For home routing roaming in clause 4.3.4.3, the H-SMF indicates in the Nsmf_PDUSession_Update Request that the UE shall not be notified. This shall result in the V-SMF not sending the N1 SM Container (PDU Session Release Command) to the UE. - Nsmf_PDUSession_StatusNotify service operation invoked by H-SMF to V-SMF and Nsmf_PDUSession_SMContexStatusNotify service operation invoked by the (V-)SMF to the AMF indicate that the PDU Session is moved to a different system. - The Npcf_SMPolicyControl_Delete service operation to PCF shall not be performed.