SOR During the UE Registration Call Flow
This section describes the SOR during the UE Registration call flow.

Step |
Description |
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1 |
UE sends the Registration Request to the VPLMN AMF. |
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2 |
The VPLMN AMF executes the registration procedure as defined in subclause 3GPP TS 23.502 [63], section 4.2.2.2.2. As part of the registration procedure, the VPLMN AMF invokes the Nudm_SDM_Get service operation message to the HPLMN UDM. This service operation helps in getting the Access and Mobility Subscription data for the UE. |
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3 |
The following are the responses from the HPLMN UDM, reciprocating to the Nudm_SDM_Get service operation message:
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4 |
When the HPLMN UDM sends the response using the Nudm_SDM_Get service operation to the VPLMN AMF, the following are the next substeps:
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5 |
As part of the registration procedure, the VPLMN AMF invokes the Nudm_SDM_Subscribe service operation to the HPLMN UDM:
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6 |
The VPLMN AMF sends the received SOR information to the UE in Registration Accept. |
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7 |
The SOR security check procedure takes place at UE. |
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8 |
The UE performs the PLMN selection procedure and ends the procedure, when:
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9 |
UE sends Registration Complete to the serving AMF with an SOR transparent container including the UE ACK:
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10 |
AMF uses the Nudm_SDM_Info service operation to provide the received SOR transparent container to the UDM in Registration Complete:
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11 |
UE performs the PLMN selection when a high priority PLMN is available. |