NTP pool

The NTP pool is a dynamic collection of networked computers that volunteer to provide highly accurate time via the Network Time Protocol to clients worldwide. The machines that are "in the pool" are part of the pool.ntp.org domain as well as of several subdomains divided by geographical zone and are distributed to NTP clients via round-robin DNS. The geographic zone selection is no longer unnecessary, as customized authoritative DNS servers that utilize geolocation software (geoip) is now used.^[2]

NTP pool

URL	www.ntppool.org/en/
IPv6 support	Yes
Launched	2003; 22 years ago (2003)[1]

As of May 2022^[update], the pool consists of 3,126 active servers on IPv4 and 1,534 active servers on IPv6.^[3][a] Because of the decentralization of this project, accurate statistics on the number of clients cannot be obtained, but according to the project's website, the pool provides time to 5–15 million systems.^[5]

The pool consists of the following parts:

• Website
• NTP time servers. Because of client growth, the project is in perpetual need of more servers.^[6][7][8] The more time servers there are in the pool, the lower the resource demand on each member. Joining the pool requires at least a broadband connection to the Internet, a static IP address, and accurate time from another source (for example, another NTP server, a DCF77 receiver, a WWVB receiver, or a GPS disciplined oscillator). Joining the server can be done on the website.
• Monitoring servers, which fetches time from joined NTP servers and compares it with a known-good value, producing a score that reflects accuracy and reliability. Only NTP servers with score greater than 10 are considered for DNS distribution.^[9]
• Specialized DNS servers, which direct clients to the actual pool servers using a combination of the requested zone and geoip. Volunteers can contact NTP pool to become one of these servers.^[2]

This project was started by Adrian von Bidder in January 2003 after a discussion on comp.protocols.time.ntp about abuse of the public stratum 1 servers.^[10][11] The system has been maintained and developed by Ask Bjørn Hansen since July 2005.^[12]

The NTP pool occasionally see NTP server misuse and abuse, mostly from corporate vendors with many users shipping buggy software.^[13][14][15] The project advises that vendors apply for their own zones, so that usage patterns are easier to keep track of.^[16]