This is because all NTP servers need access to User Datagram Protocol (UDP) port 123, and as long as the Windows Time service is running on the Windows Server 2003 operating system, port 123 remains reserved by Windows Time. Configure Internet Time (NTP) options in Windows 10 Internet Time (NTP) is a very useful way to keep your PC's time accurate automatically. Once configured, Windows will request time data periodically from time servers, so you can be sure that time and date on your device are set properly. Here is how it can be done. … NIST Internet Time Service Users are *strongly* encouraged to upgrade to the network time protocol (NTP), which is both more accurate and more robust. 2. Users of the NIST "DAYTIME" protocol on tcp port 13 are also strongly encouraged to upgrade to the network time protocol, which provides greater accuracy and requires less network bandwidth. List of TCP and UDP port numbers - Wikipedia
NTP is a UDP-based service. NTP servers use well-known port 123 to talk to each other and to NTP clients. NTP clients use random ports above 1023. As with DNS, you can tell the difference between the following: An NTP client-to-server query Source port above 1023, destination port 123. An NTP server-to-client response Source port 123
How to Configure NTP Server in Windows 2012 r2 Step by Step Dec 12, 2019 List of Top Public Time Servers · GitHub It is not advisable to mix smeared and non-smeared NTP sources (Facebook and Google use different smearing techniques from each other, so they should not be mixed either). Just thought I'd mention that for anyone who comes across this page hoping to add NTP servers from different sources.
Dec 02, 2016 · Google's turned on a set of public network time protocol (NTP) servers. You'll find the servers at time.google.com – which resolves to 216.239.35.0, a rather less pretty IP address than the 8.8.8.8 and 8.8.4.4 Google uses for its public domain-name system (DNS) servers.
NTP Server Test