URI Version Selection Logic
When two different 3GPP compliance versions are configured, the Nnrf_NFDiscovery service allows SMF to discover other NF (Network Function) instances with the services they offer, by querying the local NRF (Network Repository Function), i.e CHF, AMF, and PCF.
The Discovery response SearchResult body contains an array of NF Profile objects that satisfy the search filter criteria. The attribute data type NFServiceVersion captures the versions supported by various peer NFs.
Based on SMF profile configuration versions and the version received in the Discovery SearchResult, the SMF selects a version for peer NFs for subsequent messages.
The logic based on which the SMF selects the versions for peer NFs, is called the URI Version Selection Logic. It selects the highest version for the peer NFs.
The following table describes how the URI version selection logic selects a suitable version for peers upon receiving the NFServiceVersion as a result of the Discovery response:
SMF Compliance Configuration Versions | Discovery Search Result Versions | Selected Version for Peer NFs |
---|---|---|
V2, V1 |
V2, V1 |
V2 |
V2, V1 |
V1 |
V1 |
V1 |
V2, V1 |
V1 |
Once the version for peer NFs is selected, the subsequent message is sent using the selected version. If during the first message exchange the selected peer NF goes down, the SMF selects another peer with the same or next highest NF version.
After the first message exchange if the selected peer NFs go down, the SMF will not select another peer with the same or different version for the session.