Enter any NTP Server you would like to perform a NTP Test on. (i.e. pool.ntp.org)
The Network Time Protocol (NTP) is a protocol for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. NTP uses UDP port 123 as its transport layer. It is designed particularly to resist the effects of variable latency by using a jitter buffer.
NTP is one of the oldest Internet protocols still in use (since before 1985). NTP was originally designed by Dave Mills of the University of Delaware, who still maintains it, along with a team of volunteers.
NTP uses a hierarchical system of "clock strata". The stratum levels define the distance from the reference clock and exist to prevent cycles in the hierarchy. (Note that this is different from the notion of clock strata used in telecommunications systems.)
Stratum 0: - These are devices such as atomic (caesium, rubidium) clocks, GPS clocks or other radio clocks. Stratum-0 devices are not attached to the network; instead they are locally connected to computers (e.g. via an RS-232 connection using a Pulse per second signal).
Stratum 1: - These are computers attached to Stratum 0 devices. Normally they act as servers for timing requests from Stratum 2 servers via NTP. These computers are also referred to as time servers. Many Stratum 1 servers (for NTP v3 and earlier versions) may not actually be operating with Stratum 1 precision. As the NTP protocol is developed, it will become less and less possible for misleading Stratum 1 servers to run — instead the protocol would automatically bump the server Stratum level down accordingly.
Stratum 2: - These are computers that send NTP requests to Stratum 1 servers. Normally a Stratum 2 computer will reference a number of Stratum 1 servers and use the NTP algorithm to gather the best data sample, dropping any Stratum 1 servers that seem obviously wrong. Stratum 2 computers will peer with other Stratum 2 computers to provide more stable and robust time for all devices in the peer group. Stratum 2 computers normally act as servers for Stratum 3 NTP requests.
Stratum 3 - These computers employ exactly the same NTP functions of peering and data sampling as Stratum 2, and can themselves act as servers for lower strata, potentially up to 16 levels. NTP (depending on what version of NTP protocol in use) supports up to 256 strata.
The w3dt.net NTP Query tool can be used to query any public NTP Server (as long as it permits w3dt to query it) to help test / check server variables and maintain a NTP server.
The w3dt NTP Test tool is based off native code by ntp.org - 2008.