Feature Description
The SMF performs UPF selection from a list of all UPFs having an active association based on certain selection criteria including the query parameters. These parameters consist of DNN, pdn-type-subscription, pdn-type-session, priority, load, and Dual Connectivity with New Radio (DCNR) (only for EPS).
The 5GS and EPS core networks apply the selection mechanism to select a UPF node during the creation of a subscriber session.
The UPF selection can be based on the load of the UPFs. The load-based UPF selection distributes calls among active UPFs associated with SMF. 3GPP specifies Load Control feature as optional feature over N4 reference points. This 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 mentioned in 3GPP TS 29.244 v14.0.0 Release 14, section 6.2.3 and SMF adheres to the CP functionality.