Question: In an SBI-capable Network Application Function (NAF) discovery process, if no SBI-capable Bootstrapping Server Function (BSF) instance is available within a given Public Land Mobile Network (PLMN), how does the NAF proceed?
Option 1: The NAF selects a non-SBI capable BSF instance as a fallback.
Option 2: The NAF communicates with the BSF using legacy GBA protocols.
Option 3: The NAF sends a repeated Nnrf_NFDiscovery_Request to the NRF after a set timeout.
Option 4: The NAF uses the SBI interface towards a Zn-Proxy in the same PLMN for further resolution.
Explanation: According to specified behavior, if no SBI-capable BSF instance is available within the PLMN, the NRF responds with no information. In this scenario, the SBI-capable NAF may then attempt to communicate with the BSF using legacy GBA protocols as a fallback measure, ensuring continuity of service when SBI capabilities are not met.