A.102 Monitoring of DRBs undergoing GTP User Plane Path failures

28.5523GPP5G performance measurementsManagement and orchestrationRelease 18TS

The DRB setup procedure in NG-RAN is to assign resources in gNB and on the air interface (Uu) for one or several DRBs that will handle the QoS flows requested to setup by the core network. The gNB may map several QoS flows to the same DRB so there is no one-to-one mapping between the flows and DRBs.

At DRB setup, the gNB will handle all QoS flows mapped to one DRB the same (mapped 5QI). A QoS flow that is at a later stage mapped to an already setup existing DRB will not increment the DRB setup counters.

The DRB setup is one of the most key procedures to allocate resources in the NG-RAN to the UE per the QoS requirements. Whether or not the DRB is successfully setup has direct impact to the user experience. A failed DRB setup may directly cause service failure or degradation for an end user. So, the performance related to the DRB setup for the gNB needs to be monitored per supported mapped 5QI and per S-NSSAI.

During transient path failures (e.g. path failures not exceeding few minutes at most), maintaining the PDU session contexts associated with the peer’s IP address enables the delivery of end user services (when the path is re-established again) and this also avoids unnecessary signalling in the network for restoring those PDU sessions.
It is not intended to maintain PDU session contexts during long path failures (e.g. exceeding few minutes at most) as this would imply undesirable effects like undue charging.

The total number of active transient path failures irrespective of whether this path restores into PDU session or not is measured with this use case.