How it Works

This section describes how the SMF handles the co-located UPF selection during PDN Session Establishment in 4G network.

When the SGW-U node name is available in the CSR, SMF derives the UPF from the configuration based on the node name.

Then, SMF uses the existing UPF selection logic and derives the list of UPFs accordingly. The SMF checks if the SGW-C selected UPF exists in the derived UPF list.

If the SGW-C selected UPF is present in the derived UPF list and if its priority matches with the highest priority in the derived UPF list, then SGW-C selection UPF is selected. Otherwise, priority UPF in the derived list is selected.

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