on Twitter: "NPL's NTP servers are stratum 1, which means they are directly sync'd with a reference clock.(Likely something from https://t.co/AgHiT9WjnC ) NIC's NTP servers are stratum 2 servers which means
Artica as NTP server | Artica Wiki
Active Directory: Time Synchronization - TechNet Articles - United States (English) - TechNet Wiki
Setup Windows 2012 Server as NTP Server | Telephony-Networking Wiki | Fandom