How it Works
This section describes how this feature works.
The PCF registers with the NRF to create a passage for interacting with the other NFs to perform operations such as discovery and selection.
The overview of how NF and PCF interact through NRF in the following sequence:
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Registration: PCF registers its profile that defines the services or capabilities with the NRF. The registration service request contains the load parameters. The cluster load value is a collective value of the cluster memory and cluster CPU usage derived from Prometheus.
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Discovery: After the registration is successful, the NRF sends the information about the registered PCF instances to the (consumer NF) NFs through an NRF query. The NFs that are registered with the NRF periodically send a heartbeat in the form of an NFUpdate service. The NF discovery response carries attributes such as load, capacity.
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Selecton: When the NF wants to establish a connection with a PCF instance, it determines the appropriate instance based on the attributes such as load and location.
If the NRF receives an NF query with the preferred-locality attribute, then, NRF assigns a higher priority value (higher the value, lower the priority) to the profiles or services that do not match the preferred-locality parameter. The NRF sorts the NF profiles and services based on the load, capacity, and priority in the next step. The consumer NF determines the registered NF based on the criteria that NRF has used for sorting. For example, if UPF wants to send a service request to a PCF instance in a preferred locality, then it selects the PCF profiles with the lowest value.
The following figure depicts how these components interconnect.
