Feature Description
The SMF selects UPF from a list of all active UPFs based on the predefined query parameters.
The 5GS and EPS core networks apply the selection mechanism to select a UPF node during the creation of a subscriber session.
When the UPF selection is based on the load of the UPFs, the SMF distributes calls among active UPFs associated with SMF. 3GPP specifies Load Control feature as optional feature over N4 reference points. This functionality enables UPF to send its load information to CP functions.
To support load-based UPF selection, the SMF uses UPF-provided Load Control information in the following Packet Forwarding Control Protocol (PFCP) messages:
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Session Establishment Response
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Session Modification Response
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Session Deletion Response
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Session Report Request
Load Control procedure details are available in section 6.2.3 of 3GPP TS 29.244, Release 14. The SMF adheres to the CP functionality.