Network Time Protocol (NTP)

All NTP communications use Coordinated Universal Time (UTC). An NTP server usually receives its time from an authoritative time source, such as a radio clock or an atomic clock attached to a time server, and then distributes this time across the network. NTP is extremely efficient; no more than one packet per minute is necessary to synchronize two machines to within a millisecond of each other.

NTP uses a stratum to describe the distance between a network device and an authoritative time source:
  • A stratum 1 time server is directly attached to an authoritative time source (such as a radio or atomic clock or a GPS time source).

  • A stratum 2 NTP server receives its time through NTP from a stratum 1 time server.

Before synchronizing, NTP compares the time reported by several network devices and does not synchronize with one that is significantly different, even if it is a stratum 1.

The security features of NTP can be used to avoid the accidental or malicious setting of incorrect time. One such mechanism is available: an encrypted authentication mechanism.

Though similar, the NTP algorithm is more complex and accurate than the Simple Network Time Protocol (SNTP).


Enabling this feature results in synchronizing the system clock; therefore, it may affect all sub-systems that rely on system time.