Which stratum level is directly connected to an authoritative time source?

Stratum 1 devices are directly synchronized with an authoritative time source, such as an atomic clock or GPS receiver. These devices serve as primary time servers, distributing time to other network devices. Stratum 0 refers to the authoritative time source itself (e.g., the atomic clock), not a device connected to it. Stratum 15 represents the highest stratum level before a device is considered unsynchronized (Stratum 16), indicating a very unreliable or unsynchronized time source, not a direct connection to an authoritative source. Stratum 15 devices are also not authoritative time sources themselves; they are far removed from them.