LDAP (Lightweight Directory Access Protocol) uses port 389 for standard connections and port 636 for LDAP over SSL (LDAPS), which secures directory service communication.
Breakdown of Options:
A). 22 - SSH port, not used for directory services.
B). 389 - Used for LDAP, but not encrypted.
C). 445 - Used for SMB file sharing, not LDAP.
D). 636 - Correct answer. LDAPS (LDAP over SSL/TLS) secures directory authentication.
Reference:
CompTIA Network+ (N10-009) Official Study Guide - Domain 3.1: Compare and contrast network protocols.
RFC 4511: Lightweight Directory Access Protocol (LDAP)