, a Data Network Name (DNN) selection and a transport format type. The DNN value is the equivalent of the APN (Access Point Name). It allows the core network to choose the SMF function that will manage the IP flows inside this PDU session. The transport type of a PDU session can be IPv4 or IPv6 Internet connectivity, Ethernet connectivity or unstructured connectivity, such as the encapsulation of data in a point-to-point tunnel. The core network applies a default QoS for the PDU session. Depending on the operator's policy rules, the core network can also apply specific QoS for a set of flows in the PDU session. The SMF function will select the function of the UPF transport plane, which will relay the user traffic in the core network with the requested QoS. The application of QoS at the UPF level is achieved by transferring the routing rules defined by the SMF function into the table of the UPF function. 3.2.4.1. The session establishment procedure The session establishment procedure is performed to establish a new PDU session or to reestablish an existing PDU session. The establishment of a PDU session is: - initiated by the mobile on the NG-RAN network; - initiated by the mobile following a handover between either the NG-RAN network and the non-3GPP network, or the 4G mobile network and the 5G mobile network; - initiated by the network, which notifies the mobile of a request to establish a session. NG-RAN Network - Procedures Establishing a new PDU session can only be initiated by the mobile. When the network initiates the re-establishment of an existing PDU session, the core network sends paging, informing the mobile of the reason for the re-establishment of the session. The mobile responds with an NAS request to establish a PDU session. 1) The establishment of a PDU session by the mobile is carried out by an NAS PDU Session Establishment Request between the mobile and the AMF function, which transfers the request to the SMF function. The NAS PDU Session Establishment Request message is carried by the RRC Setup