NRF Heartbeat Internal Call Flow

The following figure shows the internal call flow related to the NRF Heartbeat feature.

NRF Heartbeat Internal Call Flow

The SMF NF heartbeat implementation helps in notifying the NRF that the SMF is operational. The default heartbeat frequency is once in 10 seconds. If the NRF returns a different heartbeat frequency, the same is used for the periodic heartbeat. As part of the heartbeat, HTTP PATCH Request to the resource URI representing the NF instance is sent to the NRF. The payload body of the PATCH Request contains a "replace" operation on the "nfStatus" attribute of the NF profile of the NF instance, and sets it to the value "REGISTERED". Other parameters like load and capacity are not supported in this release.

Like NF registration, NF heartbeat is also triggered from the elected master node manager. Also, the heartbeat continues even on the elected node manager restart.