PCF). Unified policy framework, providing policy rules to CP functions, access subscription information for policy decisions in user data repository. Authentication Server Function (AUSF). Authentication server to the UDM Unified Data Management (UDM). Generation of Authentication and Key Agreement (AKA) credentials, user identification handling, access authorization, and subscription management. The UE encryption key (UESUCI) is stored here. Application Function (AF). Application influence on traffic routing, accessing NEF, interaction with policy framework for policy control. Network Exposure function (NEF). Exposure of capabilities and events, secure provision of information from external application to 3GPP network, translation of internal/external information. NF Repository function (NRF). Service discovery function which maintains NF profiles and available NF instances. Network Slice Selection Function (NSSF). Selecting of the Network Slice instances to serve the UE, determining the allowed NSSAI, determining the AMF set to be used to serve the The way the CP works is that required CP functions are invoked when necessary to pro- vide specific network-related functions. For example, during UE registration, messages are exchanged between UE and AMF for session establishment, which involves communication to the UDM to ensure this UE is allowed on the network, where UDM invokes AUSF services. Next, a data connection (QoS flow in 5G which is the equivalent of a bearer in 4G language) needs to be built between the UE and the DN on the UP. For this purpose, the UE initiates a PDU session establishment request to the AMF (via the gNB). Once this exists by means of an established GTP-U tunnel between UPF and gNB, the gNB configures a data radio bearer (DRB) that translates this GTP-U-tunneled traffic into over-the-air traffic to the UE and SO Again, the point here is not to delve into 3GPP protocol stacks as has been done in plenty of other online and offline documentation. We want to show instead how 3GPP targets o