Relationships
The roaming status functionality relates to the UPF Ingress Interfaces feature that indicates the following types of roaming:
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Homer
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Roamer
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Visited LBO
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Visited HR
The UPF supports different GTP-U ingress interfaces. It allows a separate network for the N3 interface and N9, S5u, and S8u interfaces.
The GTP-U ingress interfaces to handle roaming and outbound calls include:
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N3—N3 is the interface between gNodeB and UPF. To handle 5G home calls, the N3 interface must be a private IP address.
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N9—The N9 interface connects two UPFs. It is the interface between intermediate I-UPF and UPF session anchor connecting different PLMN. To handle 5G outbound roaming calls, the N9 interface must be a public IP address.
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S5u—S5u is similar to the N9 interface that connects two UPFs. The interface connects the intermediate I-UPF and UPF session anchor. To handle 4G inbound calls, the S5u is set to a public IP since the SGW-U is public for enabling the S-GW.
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S8u—S8u is an inter-PLMN variant of the S5u interface. To handle 4G outbound roaming calls, the S8u interface must be a public IP address.
For more information, refer to the UPF Ingress Interfaces chapter.