Section: 5.7.2.4.1a Notification Control without Alternative QoS Profiles
Content: If, for a given GBR QoS Flow, Notification control is enabled and the NG-RAN determines that the GFBR, the PDB or the PER of the QoS profile cannot be fulfilled, NG-RAN shall send a notification towards SMF that the "GFBR can no longer be guaranteed". Furthermore, the NG-RAN shall keep the QoS Flow (i.e. while the NG-RAN is not fulfilling the requested QoS profile for this QoS Flow), unless specific conditions at the NG-RAN require the release of the NG-RAN resources for this GBR QoS Flow, e.g. due to Radio link failure or RAN internal congestion. The NG-RAN should try to fulfil the GFBR, the PDB and the PER of the QoS profile again. NOTE 1: NG-RAN can decide that the "GFBR can no longer be guaranteed" based on, e.g. measurements like queuing delay or system load. Upon receiving a notification from the NG-RAN that the "GFBR can no longer be guaranteed", the SMF may forward the notification to the PCF, see TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [45]. When the NG-RAN determines that the GFBR, the PDB and the PER of the QoS profile can be fulfilled again for a QoS Flow (for which a notification that the "GFBR can no longer be guaranteed" has been sent), the NG-RAN shall send a notification, informing the SMF that the "GFBR can be guaranteed" again and the SMF may forward the notification to the PCF, see TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [45]. The NG-RAN shall send a subsequent notification that the "GFBR can no longer be guaranteed" whenever necessary. NOTE 2: It is assumed that NG-RAN implementation will apply some hysteresis before determining that the "GFBR can be guaranteed again" and therefore a frequent signalling of "GFBR can be guaranteed again" followed by "GFBR can no longer be guaranteed" is not expected. NOTE 3: If the QoS Flow is modified, the NG-RAN restarts the check whether the "GFBR can no longer be guaranteed" according to the updated QoS profile. If the Notification control parameter is not included in the updated QoS profile, the Notification control is disabled. During a handover, the Source NG-RAN does not inform the Target NG-RAN about whether the Source NG-RAN has sent a notification for a QoS Flow that the "GFBR can no longer be guaranteed". The Target NG-RAN performs admission control rejecting any QoS Flows for which resources cannot be permanently allocated. The accepted QoS Flows are included in the N2 Path Switch Request or N2 Handover Request Acknowledge message from the NG-RAN to the AMF. The SMF shall interpret the fact that a QoS Flow is listed as transferred QoS Flow in the Nsmf_PDUSession_UpdateSMContext Request received from the AMF as a notification that "GFBR can be guaranteed again" for this QoS Flow unless the SMF is also receiving a reference to an Alternative QoS Profile for this QoS Flow (which is described in clause 5.7.2.4.2). After the handover is successfully completed, the Target NG-RAN shall send a subsequent notification that the "GFBR can no longer be guaranteed" for such a QoS Flow whenever necessary. If the SMF has previously notified the PCF that the "GFBR can no longer be guaranteed" and the SMF does not receive an explicit notification that the "GFBR can no longer be guaranteed" for that QoS Flow from the Target NG-RAN within a configured time, the SMF shall notify the PCF that the "GFBR can be guaranteed again".