Windows 7 Time Server systems utilise the SNTP protocol. SNTP stands for Simple Network Time Protocol, it is essentially a subset of NTP or Network Time Protocol. In terms of information packets transmitted to\from an SNTP server, they are identical and fully interchangeable with an NTP time server. The crucial differences are that an SNTP Time Server does not contain the complex algorithms to maintain a more accurate system time for a longer period.
TimeTools can provide SNTP Time Server systems that sync to MSF, DCF77 or GPS external time reference to provide an accurate time resource for your network inside your firewall.
Fig: SNTP Time Server NTP s5000 series