The untrusted non-3GPP access which basically corresponds to WLAN interworking with 5GCN is provided through a N3IWF. However, unlike the earlier architectures where the WLAN interworking network element (PDG/ePDG) was part of the 3GPP core network the N3IWF acts as an access network similar to the 3GPP access. This allows common procedures in both 3GPP access and non-3GPP access for registration, authentication and session handling. Paging, mobility registration and periodic registration are not supported with untrusted WLAN. Multiple PDU sessions can be established over both the 3GPP access and the untrusted WLAN and the PDU sessions can be transitioned between them. Further a multi access PDU session may be established over 3GPP access and untrusted WLAN with support for ATSSS.
1 3GPP TS 23.501: "System Architecture for the 5G System; Stage 2"
2 3GPP TS 23.502: "Procedures for the 5G System; Stage 2"
3 3GPP TS 24.501: "Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3"
4 3GPP TS 24.502: "Access to the 3GPP 5G Core Network (5GCN) via Non-3GPP Access Networks (N3AN); Stage 3"
5 3GPP TS 38.413: "NG-RAN; NG Application Protocol (NGAP)"
6 3GPP TS 23.402: "Architecture enhancements for non-3GPP accesses".
7 3GPP TS 23.234: "3GPP System to Wireless Local Area Network (WLAN) Interworking; System Description".
8 3GPP TS 33.501: "Security Architecture and Procedures for 5G System".
5GCN 5G Core Network
AKA Authentication and Key Agreement
AMBR Aggregate Maximum Bit Rate
AMF Access and Mobility Management Function
ANDSP Access Network Discovery and Selection Policy
ATSSS Access Traffic Steering, Switching and Splitting
AUSF Authentication Server Function
CM Connection Management
CP Control Plane
EAP Extensible Authentication Protocol
ePDG Evolved Packet Data Gateway
GGSN Gateway GPRS Support Node
GRE Generic Routing Encapsulation
GTPC GPRS Tunnel Protocol Control Plane
GTPU GPRS Tunneling Protocol User plane
GUAMI Globally Unique AMF Identifier
IKE Internet Key Exchange
IPsec IP Security
NAS Non-Access Stratum
N3IWF Non-3GPP Inter Working Function
NGAP Next Generation Application Protocol
N3AN Non-3GPP Access Network
PDG Packet Data Gateway
PLMN Public Land Mobile Network
PMIP Proxy Mobile IP
QFI QoS Flow Identifier
QoS Quality of Service
RM Registration Management
RQI Reflective QoS Indicator
SA Security Association
SCTP Stream Control Transmission Protocol
SMF Session Management Function
TTG Tunnel termination Gateway
UDM Unified Data Management
UE User Equipment
UP User Plane
UPF User Plane Function
WAG Wireless Access Gateway
WLAN Wireless LAN Access NetworkWLANSP WLAN Selection Policy