How it Works
The SMF performs the following steps to handle co-located UPF selection during PDN Session Establishment in 4G network.
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Upon receiving the CSR request, the SMF fetches the "SGW-U node name" and compares with the FQDN defined in UPF configuration.
The SMF skips the existing UPF selection logic and uses the UPF selected by SGW-C.
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In the absence of the SGW-U node name, the SMF follows the existing UPF selection algorithm.
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The SMF uses the existing selection logic if it is unable to derive the UPF from the configuration based on the SGW-U node name.