Relationships

The roaming status functionality relates to the UPF Ingress Interfaces feature that indicates the following types of roaming:

  • Homer

  • Roamer

  • Visited LBO

  • 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:

  • N3—N3 is the interface between gNodeB and UPF. To handle 5G home calls, the N3 interface must be a private IP address.

  • 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.

  • 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.

  • 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.