ssion_SMContextStatusNotify 19. IPv6 Address Configuration 20. Unsubscription / Deregistration Figure 11.9 - PDU Session Establishment - part 1 5G Standalone Networks The steps are as follows: The UE sends a PDU Session Establishment Request to the AMF; this is transported via the gNB. The NAS message containing the PDU Session Establishment Request within the SM container is sent to the AMF. This container includes information about the PDU session ID, Requested PDU Session Type, Requested SSC mode, 5GSM Capability PCO, SM PDU DN Request Container, and the number of packet filters. When the request type is "Initial Request," it is a request to establish a new PDU Session. If the request type is "Existing PDU Session," it means that it is referring to an existing PDU Session that is switching between 3GPP and non-3GPP access, or a handover from a 4G EPC network. The third type is that of an "Emergency Request," which is used to request a PDU Session to access emergency services. In this example, we will assume the first type - that is, "Initial Request." The AMF selects an SMF. It may use the NRF to discover SMF instances unless SMF information is available by local configuration. The AMF receives the PDU Session Establishment Request and looks into the "Request Type." In this case, it indicates an "Initial Request" and determines that the PDU session ID is unique and unused for any other. Next, it determines the DNN that the UE is attempting to connect to with the help of the information in the request message; the AMF sends the Create SM context Request message to the selected SMF. This Create SM context Request message contains information such as the SUPI, DNN, nSSAI, PDU Session ID, Serving network, and request type, among others. If the SMF has not registered with a UDM for this PDU Session ID, it will now do SO using Nudm_UECM_Registration (SUPI, DNN, and PDU Session ID). The SMF sends a UDM Registration Request. The UDM will store the information it has received from the SMF, such as the SUPI, SMF identit