Modifications for PCF-initiated gNB Transfer State
This section describes about the gNB transfer state activities in the PCF-initiated modifications call flow procedure.
The following figure describes Modifications for PCF-initiated gNB Transfer State call flow.

Step |
Description |
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1 |
The PCF sends the SMF Policy Association Modification Request to the SMF. It’s an interchangeable action as it also receives the same message from the SMF. |
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2 |
The SMF sends the Namf Comm N1N2MessageTransfer Request to the AMF. It’s an interchangeable action as it also receives the same message from the AMF. |
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3 |
The AMF sends the PDU Session Resource Modify Request to the lastRAN. |
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4 |
The lastRAN requests the RAN for paging activities. |
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5 |
The gNB performs the paging activities and retrieves the context between the RAN and the lastRAN. The lastRAN sends the Retrieve Context message to the RAN. It’s an interchangeable action as it also receives the same message from the RAN. |
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6 |
The lastRAN sends the PDU Session Resource Modify Response to the AMF. It also includes the PDU Session Resource Modify Unsuccessful Transfer IE with cause xxx-handover-triggered message. |
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7 |
The AMF processes and sends the Nsmf PDUSession UpdateSMContext message (N2 to xxx-handover-triggered) to the SMF. It’s an interchangeable action as it also receives the same message from the SMF.
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8 |
The RAN sends the N2 Path switch Request to the AMF. |
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9 |
The AMF sends the Nsmf PDUSession UpdateSMContext (N2SMlnfo) response message to the SMF.
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10 |
The SMF resends the PDU Session Resource Modify message to the AMF. It’s an interchangeable action as it also receives the same message from the AMF.
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11 |
The AMF sends the PDU Session Resource Modify message to the RAN. It’s an interchangeable action as it also receives the same message from the RAN. |
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12 |
The RAN sends the success note PDU Session Resource Modify (success) message to the AMF. It’s an interchangeable action as it also receives the same message from the AMF. |
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13 |
The AMF sends the modified response Nsmf PDUSession UpdateSMContext (N2 modify response) message to the SMF. It’s an interchangeable action as it also receives the same message from the AMF. |
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14 |
The SMF sends the report SM Policy Association Modification (rule report) message to the PCF. It’s an interchangeable action as it also receives the same message from the PCF. |