Interoperability with NRF
The Network Repository Function (NRF) is one of the key network entities in the 5G Core Network (5GC). It primarily maintains the NF profile of the available NF instances and their supported services. It permits the NF instances to subscribe to, and get notified about the registration in NRF of new NF instances. The NRF supports the service discovery function by receiving the NF Discovery Requests from NFs and providing the information of the available NF instances by satisfying specific criteria such as supporting a given service.
This use case involves the following:
-
NRF Interface—The NRF offers a platform for the NFs to communicate with each other and to exchange information for carrying out their operations. However, to build this communication framework, the NFs similar to PCF must register their profiles and services with the NRF. The NFs use the NRF's native management and discovery services to establish this framework. See NRF Interface for details.
-
NRF Subscription to Notifications—PCF supports NRF and the associated repository functions such as the interface discovery, registration for renaming NRF, change type, and removal or addition of new API attributes. PCF extends this support as per the 3GPP December 2018 specification compliance. See Network Repository Function Subscription to Notifications for details.
-
Heartbeat—The NF heartbeat configuration enables the network functions to notify their operational status to the NRF periodically. PCF invokes a heartbeat at the configured intervals. If the NRF is unavailable, then PCF switches between the registered primary, secondary, and tertiary NRF depending on their availability. See Heartbeat for more information.
-
N28 Interface—PCF discovers the NFs based on the Instance ID which the NFs provide such as CHF and UDR. See for N28 Interface and UDR Interface for details.