ikewise, the UDM within the IMS also keeps that subscriber information. Other elements, such as the TAS and the SCC application servers, must also be provisioned. The TAS, for instance, contains subscriber information if supported with supplementary service functionalities such as calling line ID hiding and call diversion. The TAS downloads these via Sh or other interfaces such as Lightweight Directory Access Protocol (LDAP)/Diameter. When the call is established, the PCF authorizes the appropriate QoS profiles for the subscribers. Depending on the network deployment, some additional services, such as Wi-Fi calling, can be supported. In this case, AAA servers are deployed. AAA servers also store the subscriber data, SO they need to be provisioned in the subscriber provisioning as well. IMS connectivity establishment Once the subscriber is correctly provisioned on the network it can establish the IMS connectivity. The subscriber must first conduct the 5G registration procedure to register with the 5G network. After the registration, the device/subscriber sends a PDU session establishment request to the network to connect to a Data Network (DN). 5G RAN 5G Core Default QoS Flow for SIP Signaling PDU Session Figure 8.4 - IMS PDU session establishment Voice over New Radio (VoNR) For a regular data subscriber, the DN is usually the internet. However, for a VoNR subscriber, the default DNs are both the internet and the IMS. Following the subsequent PDU session establishment request, the PDU session providing connectivity to the IMS is established with a default QoS flow. This default QoS flow has the 5QI value 5, and it carries SIP signaling. SIP signaling is required for the next stage, which is the IMS registration procedure. IMS registration The IMS registration procedure includes many elements. However, P-CSCF, S-CSCF, and UDM are the main elements taking place. P-CSCF serves as the ingress and the egress point to the IMS, provides security, and manages SIP message routing. S-CSCF is the registrar in the registratio