How it Works

The SMF maintains the cache data in a Cache pod. It uses the cache pod to share the NF discovery cache across multiple instances of SBI pods. The SBI pod periodically updates the cache pod on receiving an NF discovery response. All SBI pods refreshes its cache data periodically with the help of the cache pod.

Currently, the SMF does not invalidate the NF discovery cache entry even on the expiration of the validity time. If a message is sent to a NF that meets a specific criterion, the SMF looks up the cache data for further processing. During a cache look-up:

  • On a cache hit without an expired entry, the selected cached NF response is used to send a message for an endpoint selection.

  • On a cache hit with an expired entry, SMF sends NF discovery requests to NRF to fetch a new list of NF discovery responses.

  • If there is a cache miss, the SMF sends the NF discovery request again to the NRF to retrieve a new list of discovery responses.