6.3.3.2 SMF Provisioning of available UPF(s)

SMF may be locally configured with the information about the available UPFs, e.g. by OAM system when a UPF is instantiated or removed, or the SMF may become aware of a UPF via a UPF initiated N4 Association establishment (as described in clause 4.4.3 of TS 23.502 [3]).

NOTE 1: UPF information can be updated e.g. by OAM system any time after the initial provisioning, or UPF itself updates its information to the SMF via N4 node level procedures anytime after N4 Association establishment.

The UPF selection functionality in the SMF may optionally utilize the NRF to discover UPF(s). In this case, the SMF issues a request to the NRF that may include following parameters: DNN, S-NSSAI, SMF Area Identity, the requested functionalities and capabilities (e.g. ATSSS steering capabilities, functionality associated with high data rate low latency service, NAT information exposure functionality, IP or MAC filter-based packet detection functionality, operator configurable UPF capabilities, etc.). In its answer, the NRF provides the NF profile(s) that include(s) the IP address(es) or the FQDN of the N4 interface of corresponding UPF(s) to the SMF. If required and/or preferred UPF functionalities are received from UDM (see clause 5.2.3.3.1 of TS 23.502 [3]), the SMF considers this information for discovering UPF(s).

UPFs may be associated with an SMF Area Identity in the NRF. This allows limiting the SMF provisioning of UPF(s) using NRF to those UPF(s) associated with a certain SMF Area Identity. This can e.g. be used in the case that an SMF is only allowed to control UPF(s) configured in NRF as belonging to a certain SMF Area Identity.

The NRF may be configured by OAM with information on the available UPF(s) or the UPF(s) may register its/their NF profile(s) in the NRF. This is further defined in clause 4.17 of TS 23.502 [3].