QoS Flow Failures for Service Request Procedures

The SMF supports both UE and Network Service Request procedures. For these procedures, the SMF processes the received SM Context Update Request to update the N3 tunnel path from idle to active state.

The QoS flow failures for service request procedures are handled in the same way as described in the 3GPP 23.502, Section 4.2.3.2. However, QoS flow failure list is handled with the PDU Session Setup Response Transfer N2 message, which is received as SM Context Update Response when subscriber moves from Idle to Active State.

PDUIM Idle to Active Mode
QoS Flow Failures for Service Request Procedure

Step

Description

1

The SMF sends the SM Context Update Request message for the User Plane Connection State as Activated.

2

SMF sends 200 response along with PDU Session Setup Request towards AMF. AMF sends N2 message PDU Session Setup Response Transfer which contains QoS flow faliure list.

3

SMF validates failed QFIs to extract failed PCC rules and failed flows.

4

SMF updates received DL tunnel information (gNB, delete PDRs, delete QERs). After the tunnel information is updated, SMF removes URR based on failed flows and sends N4 Session Modification Request towards UPF.

5

UPF provides usage report as part of N4 Session Modification Response. SMF sends SM Context Update Response for User Plane Connection State as Activated along with released EBIs as failed EBIs and triggers internal transaction to process charging and PCF triggers.

6

SMF sends Charging Data Update Request to CHF. This request includes the details, such as session-level triggers, multi-unit information with rating-group-level triggers and usage report, customer identification information, and the PDU session charging information.

7

SMF sends internal transaction based on failed QFIs to initiate PDU UE Sync Procedure to send N1/NAS signalling. Refer to PDU UE Sync Procedure call flow diagram for N1N2 message transfer