ources to be allocated on the NG-U interface: - request for establishment of a PDU session from the AMF to a radio access node; - modification of a PDU session from the AMF to a radio access node; - release of a PDU session from the AMF to a radio access node; - notification from an NG-RAN node that some QoS flows of a PDU session are about to be released. 2.2.3.2. UE context management procedures In order to establish a PDU session, it is necessary to first secure the radio signaling bearer and data bearer exchanged on the Uu interface. The NG-RAN entity establishes a context for each UE, comprising: - security keys; - the radio capacities of the terminal and its security capacities; - the PDU session context; - the mobility restriction list. The creation of the context or the modification of the context is triggered by the AMF function. The context release is triggered either by the AMF or by the NG-RAN node (e.g. upon completion of a handover). 2.2.3.3. Mobility procedures AMF handles the mobility of UE. For each registered UE, AMF establishes a context for which the mobile is either in the idle state (CM_IDLE) or in the connected state (CM_CONNECTED). In terms of the NG-RAN node, the state of the mobile is either in RRC_IDLE or RRC_CONNECTED or RRC_Inactive. The state mapping between the NG-RAN node and AMF is: - RRC_IDLE state and CM_IDLE; NG-RAN and 5G-NR - RRC_CONNECTED state and CM_CONNECTED state; - RRC_INACTIVE state and CM_CONNECTED connected state. When the mobile is in the idle state, the location of the terminal at the core network level is defined by the TAI (Tracking Area Identity). The TAI corresponds to the coverage of a set of NG-RAN nodes. The TAI value is saved in the UE context of the mobile and in the UE context established at the AMF function. When the mobile is in the RRC_CONNECTED state, the AMF function knows the NCGI (NR Cell Global Identifier) identity of the cell on which the mobile is exchanging data. The base station manages the allocation of radio resources and can trigger session