this stage, the SMF selects the UPF that it will use to further establish the data plane for the PDU session. The allocated UE IP address or prefix, access type, RAT type, policy control triggers, serving network information, UE time zone, and user location information is communicated to the PCF using this update message: PDU session establishment in 5G PCF Response-201 Created Javascript object Notation: appiication/]son Object Member Key: sessRules Member Key: policyCtrlReqTriggers > Member Key: chargingInfo Member Key: pccRules Member Key: revalidationTime Member Key: suppFeat Figure 7.4 - Packet capture PCF Response-201 Created In Steps 15 and 16, if a charging system is allocated in the network, the CHF Create Request message is used to trigger the charging system. It is used to notify the Session Creation event to the charging system. This message would be the initial invocation and will contain an invocation sequence number that would increment with each subsequent transaction of the SMF with the CHF - for example, for reporting volume or when any other trigger condition such as a RAT type change happens, the SMF sends the subscriber an identifier and a Notify URL. The CHF responds with PDU session charging information and the list of triggers: CHF Response-201 Created Object Member Key: invocationSequenceNumber Member Key: invocationTimeStamp Member Key: pDUSessionChargingInformation Member Key: triggers Figure 7.5 - Packet capture CHF Response-201 Created In Steps 17 and 18, the SMF sends an N4 session establishment request to the selected UPF and provides the packet detection, enforcement, and reporting rules that it had received from the PCF in Steps 13 and 14. These include the PDR, QER, FAR, and URR. The UPF responds with the uplink tunnel information. Steps 19 and 20 are applicable only if N26-based interworking is enabled in the network and the SMF plays the role of PGW-c/SMF. This is a request to the AMF to assign an EPS bearer ID to this PDU session for a future handover to the 4G EPS system. If 