Stratum 1 or 2 NTP
Yesterday I had a chat with colleagues in the Hong Kong Observatory who are planning to provide v6 NTP server by end of 2011. During the discussion, they corrected me that their v4 or v6 NTP Servers are basically Stratum 1 and I previously had the idea that these servers were Stratum 2. The atomic clock itself is regarded as Stratum 0 and if it is networked to an NTP Server, the NTP Server is then a Stratum 1 facility. What we are now using in our office LAN is Stratum 2 which gets the time reference signal from a Stratum 1 source to feed to another networked segment. Counting forward, Stratum 4 is unusable as the accuracy will further be degraded after three networked segments bearing in mind that each of them introduces some latency.