Call Flow

The following figure shows the call flow details and the message exchanges in a 5G core system.

Step

Description

1

The PCF sends SmPolicyUpdateNotify to SMF, and receives an acknowledgment.

2

SMF activates the ADC rule (Predefined rule).

3

SMF maintains the predefined rule for Application ID mapping.

4

SMF sends the N4 Session Modification Request to UPF, and receives a response from UPF.

5

ADC is activated at the UPF.

6

UPF detects the packets matching ADC rule.

7

UPF sends the N4SessionUpdate request to the SMF, and receives a response from the SMF. UPF triggers Application Start.

8

SMF sends the SmPolicyUpdate Request to PCF, and receives an acknowledgment from the PCF. Optionally, the dedicated bearer is created as part of response.

9

PCF sends SmPolicyUpdateNotify to SMF, and receives an acknowledgment from SMF.

10

PCF sends dynamic rule for QCI 80 bearer, and a dedicated bearer is setup.

11

UPF switches the traffic to dedicated bearer.

12

UPF detects stop of traffic on dedicated bearer.

13

UPF sends the N4SessionUpdate request to the SMF, and receives a response from the SMF. UPF triggers Application Stop.

14

SMF sends the SmPolicyUpdate Request to PCF, and receives an acknowledgment from the PCF. Optionally, the dedicated bearer is removed as part of response.

15

PCF sends SmPolicyUpdateNotify to SMF, and receives an acknowledgment from SMF.

16

PCF sends removal of dynamic rule for QCI 80 bearer, and the dedicated bearer is removed.