Feature Description
The SMF leverages the 3GPP provision for the UEs that can support both 5G and 4G NAS to connect to E-UTRAN and 5G core network. With this provision, the SMF includes the EPS interworking support and acts as PGW-C+SMF. The SMF uses the S5 or S8 interface to receive the 4G Session Creation Request. The interfaces, such as the Gx, Gy, or Gz, that are used for a 4G session creation are replaced with the corresponding 5G core SBI interfaces, such as the NPCF and NCHF.
After a PDU session is created on PGW-C+SMF through E-UTRAN, MME, and S-GW, the SMF can perform the 4G to 5G data session handover.