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NTP Servers.

The following lists contains the time servers we recommend based on their availability.

NTP Associations

An NTP association can be one of the following:

A peer association—The device can either synchronize to another device or allow another device to synchronize to it.

A server association—The device synchronizes to a server.

You need to configure only one end of an association. The other device can automatically establish the association.

All users should ensure that their software NEVER queries a server more frequently than once every 4 seconds. Systems that exceed this rate will be refused service. In extreme cases, systems that exceed this limit may be considered as attempting a denial-of-service attack.

(NTP) is a UDP-based service. NTP servers use well-known port UDP/123 to talk to each other and to NTP clients.

NIST – National Institute of Standards and Technology

time-d-g.nist.gov129.6.15.27NIST, Gaithersburg, Maryland
time-a-g.nist.gov129.6.15.28NIST, Gaithersburg, Maryland
time-b-g.nist.gov129.6.15.29NIST, Gaithersburg, Maryland
time-c-g.nist.gov129.6.15.30NIST, Gaithersburg, Maryland
time-a-b.nist.gov132.163.96.1NIST, Boulder, Colorado
time-b-b.nist.gov132.163.96.2NIST, Boulder, Colorado
time-c-b.nist.gov132.163.96.3NIST, Boulder, Colorado
time-d-b.nist.gov132.163.96.4NIST, Boulder, Colorado
time-a-wwv.nist.gov132.163.97.1WWV, Fort Collins, Colorado
time-b-wwv.nist.gov132.163.97.2WWV, Fort Collins, Colorado
time-c-wwv.nist.gov132.163.97.3WWV, Fort Collins, Colorado
time-d-wwv.nist.gov132.163.97.4WWV, Fort Collins, Colorado

USNO – United States Naval Observatory

tick.usno.navy.mil192.5.41.40Washington, DC
tock.usno.navy.mil192.5.41.41Washington, DC
ntp2.usno.navy.mil192.5.41.209Washington, DC
tick.usnogps.navy.mil204.34.198.40Colorado Springs, CO
tock.usnogps.navy.mil204.34.198.41Colorado Springs, CO
Updated on September 5, 2021

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