on-Function-influenced traffic steering authorization 5.3.6 Network Exposure Function Exposes 5G Core capabilities and events to external applications. Uses the UDR as its data source. Allows third parties to securely provision information to the 5G Core (e.g. Expected UE Behavior). Handles masking of sensitive network information toward external parties. 5.3.7 Network Repository Function Maintains the network function (NF) profile of available NF instances and their sup- ported services, and provides NF discovery and selection Selection criteria can include location (latency), load, Data Network Name (applica- tion), access network type, slice, etc. Provides much more granular policies and dynamic capabilities when compared to Domain Name System (DNS) selection 5.3.8 Network Slice Selection Determines the candidate AMF(s) or AMF Set to be used to serve the UE Selects which slices the UE can connect Takes care of mapping slice specific identifiers 5.3.9 Non-3GPP Interworking Function The Non-3GPP Inter Working Function (N3IWF) provides support to connect UEs via non-3GPP access (only untrusted Wi-Fi access in Release 15). This is enabled with the following primary capabilities: Support of IPsec tunnel establishment with the UE in order to authenticate and autho- rize it to access the 5G core Establishes IPsec Security Association to support PDU Session traffic Performs tasks related to user plane traffic such as relaying uplink and downlink user plane packets between UE and UPF and packet marking Handling of control plane traffic such as relaying NAS signaling between UE and AMF and passing signaling from SMF related to PDU session and QoS 5.3.10 Auxiliary 5G Core Functions Table 5.1 presents other network functions as introduced in 3GPP Release 15. 5.4 5G RAN Architecture Table 5.1 Auxiliary 5G core network functions. Name of network function Primary functionality Short Message Service Provides necessary interworking functions to enable Short Message Function (SMSF) service between 5G UE and legacy SMS functiona