 and mechanisms for resource reservation for packet data streams. The functions supported over the NG interface include the follow- ing [17]: Paging function which supports transmission of paging requests to the NG-RAN nodes that are part of the paging area to which the UE is registered. UE context management function which allows the AMF to establish, modify, or release the UE context in the AMF and the NG-RAN node in order to support user-specific sig- naling on NG interface. Mobility function for UEs in ECM-CONNECTED which includes the intra-system handover function to support mobility within NG-RAN and inter-system handover func- tion to support mobility from/to EPS system including the preparation, execution, and completion of handover via the NG interface. 5G Network Architecture 115 PDU session function that is responsible for establishing, modifying, and releasing the involved PDU sessions NG-RAN resources for user data transport once the UE context is available in the NG-RAN node. NAS signaling transport function provides means to transport or re-route a NAS mes- sage for a specific UE over the NG interface. NG-interface management functions which provide mechanisms to ensure a default start of NG-interface operation and handling different versions of application part implemen- tations and protocol errors. The interconnection of NG-RAN nodes to multiple AMFs is supported in the 5G system archi- tecture. Therefore, a NAS node selection function is located in the NG-RAN node to determine the AMF association of the UE, based on the UE's temporary identifier, which is assigned to the UE by the AMF. If the UE's temporary identifier has not been assigned or is no longer valid, the NG-RAN node may consider the slicing information to determine the AMF. This functionality is located in the NG-RAN node and enables proper routing via the NG interface. As shown in Fig. 1.53, each NG-RAN node is either a gNB, that is, an NR base station, pro- viding NR user-plane and control-plane protocol terminations toward the UE 