PresenTense Time Server is a multi protocol time server. This
means PresenTense Time Server can acquire accurate time from various different time sources using a number of protocols and in turn
distribute accurate time to clients using a range of network time protocols. Because time protocols differ in the degree of accuracy
they facilitate, they each serve different purposes.
Many UNIX servers traditionally offer time on port 37 via UDP and TCP, but the accuracy of the time protocol (RFC
868) is limited to the nearest second. See also Time Protocols & Accuracy.
PresenTense Time Server offers time according to (RFC 868 ) as a matter of course and in order to complement
its primary time services. However, the time protocol according to RFC 868 is insufficient for all but the
most rudimentary local area network time synchronization needs as it makes no provision to account for network delays or other network
errors to facilitate its limited one second accuracy. For this reason, we will focus on newer, more sophisticated network time
protocols: the Simple Network Time Protocol (SNTP) & the Network Time Protocol (NTP).
SNTP and NTP both use port 123 and share a common packet format. Because of this, SNTP hosts may interoperate with NTP hosts. Both NTP
and SNTP compensate for network delays and other network errors. Using SNTP a theoretical precision of microseconds can be achieved.
However, NTP distinguishes itself from SNTP in several important ways. NTP effects synchronization of a computer to an accurate time
source in a more elegant fashion. Rather than simply correcting the local system time to bring it into agreement with the time source
in an "ad hoc" fashion, NTP aims to gradually bring the local clock into step with the accurate time source via small,
incremental adjustments to the system time or by tiny adjustments to the system clock frequency. Further, NTP employs a range of
sophisticated error mitigation methods and performs statistical averaging of time samples it collects. Because of this, NTP
facilitates a much greater degree of accuracy than SNTP and thus minimizes clock hopping and other erratic clock behavior.
Until version 3.4, PresenTense Time Server shipped with its own, built-in error mitigation and statistical averaging facilities.
Starting with version 3.5, PresenTense Server also includes a plug-in, distributed as a DLL, which employs the code base of UNIX XNTPD
and supports NTP version 3 & 4 according to RFC 1305. This plug-in is distributed with all versions of
PresenTense Time Server free of charge. If you require the newest, industry standard version of NTP, the use of the NTP4 Plug-in is