The SMF supports interworking with EPS using the N26 interface (which is an inter-CN interface between the MME and the 5GS AMF) to enable interworking between the Evolved Packet Core (EPC) and the NG core networks. Support of the N26 interface in the network is optional for interworking. The N26 interface supports a subset of the functionalities over S10 interface to enable interworking. The UE uses the EPC NAS or 5GC NAS procedures that are based on the core network. The SMF supports QoS flow failures for access and mobility procedures.
The following features are related to this use case :
* 4G to 5G Data Session Handover Support
* Timers Support
* EPS Interworking
* Flow Failure Handling for Access and Mobility Procedures
