Non-roaming 5G PDU Establishment with N4 Optimization Call Flow
This section describes the call flow of the non-roaming 5G PDU establishment with N4 optimization.

Step | Description |
---|---|
1 |
UE sends the PDU session establishment request to AMF. |
2 | AMF sends the Nsmf PDU session CreateSMContext request to SMF+PGW-C. |
3 | SMF+PGW-C sends the N10 Registration Request to UDM. Then, UDM sends the N10 Registration Response to SMF+PGW-C. |
4 |
SMF+PGW-C sends the N10 Subscription Fetch Request to UDM. Then, UDM sends the N10 Subscription Fetch Response to SMF+PGW-C. |
5 |
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. |
6 |
SMF+PGW-C sends the Nsmf PDU Session CreateSMContext Response to AMF. |
7 |
SMF+PGW-C sends the N7 Policy Create Request to PCF. Then, PCF sends the N7 Policy Create Response to SMF+PGW-C. |
8 |
SMF+PGW-C sends the N7 Policy Update Request to PCF. Then, PCF sends the N7 Policy Update Response to SMF+PGW-C. |
9 |
SMF+PGW-C sends the N40 Charging Data Request to CHF. Then, CHF sends the N40 Charging Data Response to SMF+PGW-C. |
10 |
SMF+PGW-C sends the N4 Session Establishment Request to UPF. SMF creates a tunnel for both 5G and other RAT (4G). |
11 |
After the creation of the tunnel, UPF sends the N4 Session Establishment Response to SMF+PGW-C. |
12 |
SMF+PGW-C initiates the EBI allocation procedure. Then, SMF+PGW-C sends the Namf Communication N1N2Message Transfer request to AMF. |
13 |
After the N1 PDU Session Establishment is accepted and the N2 PDU Resource Setup Request is sent, SMF+PGW-C sends the Nsmf PDU Session UpdateSMContext Request (N2 PDU Resource Setup Response) to SMF+PGW-C. |
14 |
SMF+PGW-C sends the N4 Session Modification Request to UPF. This request includes the gNB tunnel details. |
15 |
UPF sends the N4 Session Modification Response to SMF+PGW-C. The response includes the updated FAR and the gNB tunnel details. |
16 |
SMF+PGW-C sends the Nsmf PDU Session UpdateSMContext Response to AMF. |