Which NTP service is a best practice to ensure that all network devices are synchronized with a reliable and trusted time source?

Redundant NTP provides failover so devices remain synchronized if one server becomes unavailable. Authentication (via MD5 or SHA keys) ensures devices only accept time updates from trusted sources, preventing NTP spoofing or man-in-the-middle attacks that could desynchronize logs and security systems.

Unauthenticated NTP leaves devices vulnerable to NTP spoofing attacks, where an attacker injects false time data to corrupt logs or bypass time-based security controls.

Relying on a single AD domain controller as the sole time source lacks redundancy and AD DCs may rely on inaccurate internal clocks unless explicitly configured with an external stratum-1 or stratum-2 source.

Per-device local NTP results in clock drift between devices, causing timestamps to diverge, which breaks log correlation and violates the fundamental purpose of time synchronization.