el basis. Within the 5GS, a QoS flow is controlled by the SMF and may be preconfigured, estab- lished via the PDU session establishment procedure, or the PDU session modification proce- dures. Any QoS flow is characterized by a QoS profile provided by the SMF to the AN via the AMF over N2 reference point or is preconfigured in the AN; one or more QoS rule(s) which can be provided by the SMF to the UE via the AMF over N1 reference point and/or derived by the UE by applying reflective QoS control; and one or more SDF templates pro- vided by the SMF to the UPF. In 5GS, the QoS flow of the default QoS rule is required to be established for a PDU session and to remain active throughout the lifetime of the PDU session. The QoS flow of the default QoS rule is a non-GBR QoS flow [3]. A QoS flow may be either GBR or non-GBR depending on its QoS profile, which contains the corresponding QoS parameters. For each QoS flow, the QoS profile includes the follow- ing parameters [3]: 5G QoS identifier (5QI) For each non-GBR QoS flow, the QoS profile may include RQA For each GBR QoS flow, the QoS profile includes GFBR and MFBR for uplink and downlink In case of a GBR QoS flow only, the QoS parameters may include notification control and maximum packet loss rate for uplink and downlink Each QoS profile has one corresponding QFI, which is not included in the QoS profile itself. The 5QI value may indicate that a QoS flow has signaled QoS characteristics, and if so, the QoS characteristics are included in the QoS profile. The UE performs classification and marking of uplink user-plane traffic, that is, the association of uplink traffic to QoS flows based on the QoS rules. These QoS rules may be explicitly pro- vided to the UE via the PDU session establishment/modification procedure, preconfigured in the UE or implicitly derived by the UE by applying reflective QoS. A QoS rule contains a QoS rule identifier which is unique within the PDU session, the QFI of the associated QoS flow and 178 Chapter 1 except for the default QoS rule a pac