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.
| 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. |