tablishment of the sessions; - the type of service in an S-NSSAI (Single - Network Slice Selection Assistance Information). The PDU session consists of: - a tunnel in the core network between the UPF (User Plane Function) and the gNB (gNode B) entity via the N3 interface; - one or more radio supports (bearer). The QoS (Quality of Service) model is based on flow management. User traffic is classified into Service Data Flows (SDF). An SDF service data flow refers to a group of flows associated with a service. 5G-NR Radio Interface - Data Link Layer For the 4G mobile network, QoS management is controlled at the bearer level. The EPS bearer is a tunnel that groups together different SDFs that have the same QoS. A TFT (Traffic Flow Templates) filter makes it possible to group together the service flows towards the corresponding bearer. The TFT filter is configured by the operator according to five parameters: source and destination IP address, source and destination port, and the identity of the protocol. For the 5G mobile network, the QoS flow is characterized by a QoS profile provided by the SMF function to the NG-RAN radio access. The QoS profile contains a set of rules for determining the processing of the flow on the radio interface: - class of service identifier (5QI); - the allocation and retention priority ARP (Allocation and Retention Priority). The 5QI class of service identifier corresponds to the index of a table on which the flow characteristics are predefined: - priority; - the flow transfer mechanism: flow at guaranteed rate (GBR) or not guaranteed (non-GBR); - the rate of packet loss; - the RTT time relating to the transfer of the flow in an end-to-end PDU session. Unlike 4G, for which end-to-end connectivity (EPS bearer) was characterized by a unique QoS, the 5G PDU session carries flows, and each flow is characterized by its own QoS. Thus, different QoS flows are transported in the same PDU session. PDU session Data Radio Bearer 1 Tunnel NG-U Flow (QoS) Data Radio Bearer 2 (QoS) (QoS) Figure 8.3. PDU