In the NTP (Network Time Protocol) hierarchy, a stratum level defines the distance from the reference clock. A Stratum 0 device is a high-precision timekeeping device such as an atomic clock or GPS clock that is not directly connected to the network. A Stratum 1 server is directly connected to the Stratum 0 device and serves time to lower-stratum servers on the network. Therefore, a server that is connected directly to an authoritative time source is considered a Stratum 1 server. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) v1.1 Reference: https://www.cisco.com/c/en/us/td/docs/routers/asr920/con figuration/guide/bsm/16-6-1/b-bsm-xe-16-6-1-asr920/bsm-timecalendar- set.html