5G-NR: NRF


Role of NRF in 5G architecture:

Network Repository Function (NRF)

The NRF maintains a record of all the 5G elements that are available in the network and their supported services. It allows other NF instances to subscribe and be notified of registrations from NF instances of a given type


The NRF supports discovery mechanisms that allows 5G elements to discover each other and get updated status of the desired elements.

The NRF supports the following functions:

  • Maintains the profiles of the available NF instances and their supported services in the 5G core network
  • Allows consumer NF instances to discover other providers NF instances in the 5G core network
  • Allows NF instances to track the status of other NF instances

 It supports the above functions through the following services:

  • Management Services (Nnrf_NFManagement)
  • Discovery Services (Nnrf_NFDiscovery)

Management Services (nrf_NFManagement.

This will handles the following service operations:
  • Receives and handles NFRegister service requests from the Nfs.
  • Receives and handles NFDeregister service requests from the NFs
  • Stores the registered profiles in its own data store using the database service.
  • Receives and handles NFDeregister service requests from the Nfs.
  • Receives and handles the Heart-beat messages from the NFs
  • Monitors the heart-beat expiry, mark the NF profiles as suspended and take appropriate action on the suspended NF profiles.
  • NF profile Retrieval.
  • Receives and handles NFStatusSubscribe service requests from the NFs.
  • Receives and handles NFStatusUnsubscribe service requests from the NFs.
  • Receives and handles NFNotify service requests from the NFs
  • Stores the subscription data in its own data store using the database service
Discovery Services (Nnrf_NFDiscoveryService)

This will handles the following service operations:
  • Receives and handles NFDiscover service requests from the Nfs.

 
NRF Functions/Procedure Support:

The NRF interacts with every other element in the 5G core network and it supports the above functions through the following services over HTTPS protocols:
  • Management Services
  • Discovery Services


Supports the following Functions/Procedure-
1) NRF Management Services-
The NRF Management service is identified by the service operation name Nnrf_NFManagement. NRF supports the following management services.
 
Register NF instance (NFRegister):- It allows an NF Instance to register its NF profile in the NRF; it includes the registration of the general parameters of the NF Instance, together with the list of services exposed by the NF Instance. This service operation is not allowed to be invoked from an NRF in a different PLMN. 
 
Update NF instance (NFUpdate): Enables an NF instance to partially update or replace the parameters of its NF profile in the NRF. It also allows to add or delete services provided by the NF instance.
 
De-register NF instance (NFDeregister): It allows an NF Instance to de-register its NF profile in the NRF, including the services offered by the NF Instance. This service operation is not allowed to be invoked from an NRF in a different PLMN.
 
Subscribe to Status (NFStatusSubscribe): Enables an NF instance to subscribe the status changes of other NF instances registered in the NRF.
 
Unsubscribe to Status (NFStatusUnsubscribe): Enables an NF instance to unsubscribe the status changes of other NF instances.
 
Receive Notifications of Status (NFStatusNotify): Enables the NRF to notify changes status of NF instances to any subscriber of NF status. Changes also include information regarding newly registered and de-registered NFs.


2) Discovery Service:

The NRF Discovery service is identified by the service operation name Nnrf_NFDiscoveryService.
Nnrf_NFDiscoveryService- It also allows an NF to subscribe to be notified of registration, de-registration and profile changes of NF Instance along with their NF Services.





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