How it Works

The SMF performs the following steps to handle co-located UPF selection during PDN Session Establishment in 4G network.

  1. 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.

  2. In the absence of the SGW-U node name, the SMF follows the existing UPF selection algorithm.

  3. 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.