y, SMF address, and the associated DNN and PDU Session ID. The UDM then responds with a UDM registration response if Session Management Subscription data for the particular SUPI, DNN, and S-NSSAI combination is not available locally. SMF then retrieves it using Nudm_SDM_Get (SUPI, Session Management Subscription data, DNN, and S-NSSAI) and also subscribes to be notified whenever a modification is made to this subscription. The subscription data contains information about the Allowed PDU Session Type, Allowed SSC modes, default 5QI, ARP, and Session-AMBR, all of which can be used to determine the characteristics of the session that has been initiated. The SMF then sends a PDU Session Create SM Context Response to the AMF, which includes a cause field and the context ID. The cause field will contain either an accept or a reject cause. The accepted scenario will contain the aforementioned context ID. The cause also determines the fate of the transaction SO far as being successful or unsuccessful. Optional: secondary authorization and authentication. If this step is needed, then an AAA server is needed for the transaction to complete the authorization and authentication process. PCF selection is undertaken by the SMF. This can happen with the PCF ID provided by the AMF, or the PCF retrieved by querying the NRF or by local configuration. The SM Policy Association 5G SA network design fundamentals Establishment procedure is then undertaken by the SMF to get the default PCC rules from the PCF, which will be used by the PDU Session that is going to be established. 8. Since the request type is "Initial Request," the SMF selects an SSC mode for the PDU session and also selects UPFs accordingly. At this stage, the SMF also allocates an IP address to the UE. The SMF performs the SM Policy Association Modification procedure, which can contain information about the policy control trigger conditions that have been met. Most importantly, it informs the PCF of the IP address prefix that it allocated to the UE in the previous step