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. Work is being done to make the geographic zone selection unnecessary via customized authoritative DNS servers that utilize geolocation software.
As of May 2022[update], the pool consists of 3,126 active servers on IPv4 and 1,534 active servers on IPv6. 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. Because of client growth, the project is in perpetual need of more servers.
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 GNSS receiver).
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. The system has been maintained and developed by Ask Bjørn Hansen since July 2005.
- "What the NTP Pool can offer". Retrieved April 29, 2011.
- "All Pool Servers". Retrieved December 14, 2019.
- "Pool Capacity". Retrieved April 2, 2018.
- "Reached 500 servers - Welcome Slashdot". Ask Bjørn Hansen. January 15, 2006.
- "Yes, the pool needs more servers". Ask Bjørn Hansen. August 11, 2009.
- "The NTP Pool needs more servers". Ask Bjørn Hansen. June 21, 2012.
- "Public servers abuse". David L. Mills. January 21, 2003.
- "ntp DNS round robin experiment". Adrian 'Dagurashibanipal' von Bidder. January 27, 2003.
- "The Future is Bright, The Future is ...". Adrian 'Dagurashibanipal' von Bidder. July 24, 2005.