5.45.3 Congestion information monitoring

The NG-RAN may be required to provide the UL and/or DL QoS Flow congestion information to UPF (i.e. a percentage of congestion level for exposure). The UPF may be required to monitor and expose the UL and/or DL QoS Flow congestion information reported from the NG-RAN.

QoS monitoring request for congestion information provided by the SMF to the NG-RAN is to trigger the NG-RAN to measure and report UL and/or DL QoS Flow congestion information to PSA UPF as defined in 5.37.3.

NOTE 1: How the RAN measures and reports the congestion information is up to RAN implementation.

NOTE 2: It is assumed that the RAN reports whenever there is a change in the percentage of packets to be marked with ECN for L4S marking and/or congestion information. The granularity of change in percentage determination is up to RAN implementation.

For the reporting of the congestion information from PSA UPF, the periodical reporting is not applied and only the Reporting frequency 'event triggered' applies, see clause 5.8.2.18.

The PSA UPF reports the received UL and/or DL QoS Flow congestion information to the target NF as instructed by the QoS Monitoring request (see clause 5.8.2.18) from the SMF.

Only ECN marking for L4S in NG-RAN (as described in clause 5.37.3) or QoS monitoring of congestion information may be requested to NG-RAN for a QoS Flow. QoS Monitoring of congestion information for exposure and ECN marking for L4S (in NG-RAN or UPF) are mutually exclusive, therefore, measurements of Congestion information on a QoS Flow are not exposed in QoS Monitoring reports if SMF enables ECN marking for L4S (see clauses 5.37.3 and 5.37.4).