Understanding NTP Stratum Levels and Reported Time Authority

In Network Time Protocol (NTP), stratum is a numeric value that describes the distance between a device and its time reference. Stratum values help downstream systems understand the relative position of a time source within a time distribution hierarchy.

Stratum is informational. It does not directly measure time accuracy, stability, or correctness.

• Stratum 0: the primary reference itself (for example, a GNSS reference or other primary time standard). Stratum 0 sources do not participate directly in NTP.
• Stratum 1: a time server directly synchronized to a Stratum 0 reference.
• Stratum 2 and higher: systems that receive time from an upstream NTP server, with the stratum value incrementing by one at each level.
• Stratum 16: typically indicates an unsynchronized state.

Stratum describes how time is distributed, not how well it is maintained.

By default, Masterclock GMR devices automatically report their stratum based on the active time reference and synchronization state. When a valid primary reference is present, the reported stratum reflects the device’s position relative to that reference.

Downstream systems typically increment the reported stratum value as they redistribute time further into a network.

Masterclock GMR devices also support manual stratum configuration. When manually set, the device reports the specified stratum value regardless of the reference type or synchronization method in use.

For example, a device may be configured to report itself as Stratum 1 even if it is not directly synchronized to a primary reference.

Manual stratum configuration affects reported stratum only. It does not change time accuracy, reference quality, holdover behavior, or output stability.

Downstream systems may rely on the reported stratum value when making source selection decisions.

• A lower stratum does not guarantee better time accuracy.
• Two devices reporting the same stratum may have very different time quality.
• Stratum alone should not be used as the sole indicator of time reliability.

Stratum is intended to describe hierarchy, not performance.

• Stratum indicates distance from a primary reference, not absolute accuracy.
• Masterclock devices can report stratum automatically or be manually set to report a specific value.
• Manual stratum settings change the reported value, not the underlying time quality.