R.6.4 SNTP restrictions

In theory, servers can be SNTP servers and NTP servers can be SNTP clients of other servers. This is very strongly discouraged. The SNTP errors can be substantial, and the clients of a server using SNTP will not have the statistical information needed to assess the magnitude of these errors. It is feasible for SNTP clients to use NTP servers. The SNTP protocol packets are identical to the NTP protocol packets. SNTP differs in that some of the statistical information fields are filled with nominal SNTP values instead of having actual measured values.