Using AD Query, which protocol do security gateway connections use to connect to the Active Directory Domain Controllers?

The correct answer is Lightweight Directory Access Protocol (LDAP).

LDAP is specifically designed for accessing and managing directory information services. In the context of Active Directory, it provides a protocol for querying and modifying user and resource information stored in the directory. When a security gateway needs to connect to Active Directory Domain Controllers to perform functions such as user authentication or information queries, it typically uses LDAP because it facilitates efficient communication with directory services, allowing for operations like searching for user accounts or group memberships.

The other protocols listed serve different purposes that are not directly related to querying Active Directory. For instance, Windows Management Instrumentation (WMI) is more focused on management and monitoring tasks in Windows environments rather than directory services access. Hypertext Transfer Protocol Secure (HTTPS) is primarily used for secure web communications, while Remote Desktop Protocol (RDP) allows for remote access to machines rather than directory queries. Thus, LDAP is the most suitable and appropriate choice for this type of connection to Active Directory.