Which protocol works with port 389 for centralized client information?

The correct answer is LDAP, which stands for Lightweight Directory Access Protocol. This protocol operates over port 389 and is used primarily to access and manage directory information services over an IP network. LDAP is particularly effective in environments where centralized client information is necessary, such as in enterprise settings for user authentication, managing directory services, and querying active directory.

LDAP allows organizations to store user credentials and other related information in a hierarchical structure, which can then be accessed by various applications and services to authenticate users centrally. This centralized management simplifies the administration of users and resources and enhances security by allowing policies to be applied consistently across the organization.

The other options listed do not utilize port 389 for their primary functions or are not primarily designed for the purpose of centralized client information management like LDAP is. For example, Diameter is a protocol used in telecommunications and often operates over port 3868, while EAP-TLS and EAP-MD5 are authentication protocols that serve different purposes in network security.