Non-roaming 4G PDN Attach with N4 Optimization Call Flow

This section describes the call flow of the non-roaming 4G PDN attach with the N4 optimization.

Non-roaming 4G PDN Attach with N4 Optimization Call Flow
Non-roaming 4G PDN Attach with N4 Optimization Call Flow Description
Step Description
1

MME sends the Create Session Request to S-GW.

2 S-GW sends the Create Session Request to SMF+PGW-C.
3

SMF+PGW-C sends the N10 Subscription Fetch Request to UDM. Then, UDM sends the N10 Subscription Fetch Response to SMF+PGW-C.

4

SMF+PGW-C sends the N10 Subscribe to Notify Request to UDM. Then, UDM sends the N10 Subscribe to Notify Response to SMF+PGW-C.

5

SMF+PGW-C sends the N7 Policy Create Request to PCF. Then, PCF sends the N7 Policy Create Response to SMF+PGW-C.

6

SMF+PGW-C sends the N7 Policy Update Request to PCF. Then, PCF sends the N7 Policy Update Response to SMF+PGW-C.

7

SMF+PGW-C sends the N40 Charging Data Request to CHF. Then, CHF sends the N40 Charging Data Response to SMF+PGW-C.

8

SMF+PGW-C sends the N4 Session Establishment Request to UPF. SMF creates tunnel for both 5G and other RAT (4G).

9

After the creation of the tunnel, UPF sends the N4 Session Establishment Response to SMF+PGW-C.

10

SMF+PGW-C sends the Create Session Response to S-GW. This response includes the 4G default bearer tunnel information.

11

S-GW sends the Create Session Response to MME.