How it Works

The UPF initiates an N4 Association Setup request to set up an association with SMF.

The following is a high-level summary of how SMF selects the UPF node for the core network:

  • The SMF selects the UPF node for EPS and 5GS sessions based on the following parameters:

    • DNN

    • Network slice

    • DCNR (only for EPS calls)

    • Pdn-type-subscription

    • Pdn-type-session

  • The SMF/PGW-C enables you to define the UPF selection criteria which it uses to query the appropriate node.

  • If multiple UPFs match the SMF's selection criteria, then SMF selects the active UPFs and sorts them based on their priority and load information. The SMF then attempts to access the UPF one by one until the N4 Establishment is successful.