NTP: The Network Time Protocol

NTP users are strongly urged to take immediate action to ensure that their NTP daemons are not susceptible to use in a distributed denial-of-service (DDoS) attack. Please also take this opportunity to defeat denial-of-service attacks by implementing ingress and Egress filtering through BCP38.

A new set of mode 6 vulnerabilities has been discovered and, while these vulnerabilities can be reduced by making sure you have restrict default … noquery in your ntp.conf file, the best and most complete way to avoid these vulnerabilities is to install and deploy ntp-4.2.8 which was released on 18 December 2014.

Please see the NTP Security Notice for vulnerability and mitigation details.

NTF needs your help to qualify to participate in the Combined Federal Campaign, so we can continue our mission to improve network time. We only need a few thousand dollars more by December 31st - any sized donation helps! Please join an NTF Consortium or make a donation to NTF now! THANKS!

Welcome to, home of the Network Time Protocol project.

This page is home for the NTP Project (R&D). This web site, and all pages directly contained within, are in the public domain. Some portions of this site may be copyrighted by other authors. Please contact the webmaster with any questions regarding copyright. The NTP software distribution is copyrighted, as described in the NTP copyright page.

NTP is a protocol designed to synchronize the clocks of computers over a network.

NTP version 4, a significant revision of the previous NTP standard, is the current development version. It is formalized by RFCs released by the IETF.

The NTP Project (R&D)

The NTP Project conducts Research and Development in NTP and produces the Official Reference Implementation of NTP along with the Implementation Documentation. Background information about NTP, along with briefings and a bibliography, are available at the Network Time Synchronization Project Page.

The NTP Public Services Project

The NTP Public Services Project, which is hosted by Internet Systems Consortium, Inc., provides support and additional development resources for the Official Reference Implementation of NTP. The available resources include:

Please direct comments and questions about this web site to the NTP Project webmaster. To contact the NTP Public Services Project web maintainers or any member of the NTP developer team, please see the NTP Public Services Project Contact Page.