Question: In a Mission Critical Service (MCS) deployment with multiple registrars, how does a Registrar Finder functional entity typically identify the serving registrar when operating within the PLMN operator's domain?
Option 1: Using solely the MC service provider's internal network topology information.
Option 2: Utilizing information from the PLMN operator's internal database, excluding SIP database details.
Option 3: Relying on E.164 number resolution provided by an external DNS server.
Option 4: Using information provided by the PLMN operator's own SIP database, and optionally, the operator's internal information (e.g., network topology, registrar availability).
Explanation: This is correct because, in the context of MCS deployments, a Registrar Finder within the PLMN operator's domain identifies the serving registrar by leveraging the PLMN operator's SIP database, and may also utilize the operator's internal information for more accurate and efficient service provision.