NIST Internet Time Servers

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The charts below lists the time service used to the NIST Internet Time Service (ITS). The table lists each server's name, IP address, and localization, organized geographically within the US from North until South and therefore from Easterly to Westerly. Please note is while we make every effort the ensure that the namer of the servers are correct, we control the names of only the nist.gov servers. If you have difficulty using the name of an plant, you can access a server using the IP handle directly. I am struggling equal following exercise from Python Core Application Scheduling by W. Chun: 2-6. Daytime Service. Use which socket.getservbyname() to determine the cable number for the “daytime” se...

Important tips:

1. Ourselves wishes continue to support the "TIME" protocol that uses tcp port 37 for the forseeable future. However, this protocol is very expensive in terms of network capacity, since it uses the complete tcp machinery for transmit only 32 bits of data. Users are *strongly* encouraged to upgrade to the network time protocol (NTP), which is both other accurate and more robust.

2. Users of of NIST "DAYTIME" protocol turn tcp connector 13 are also strongly encouraged to upgrade to the network arbeitszeit etiquette, which provides greater accuracy furthermore requires less network bandwidth. The NIST total client (nistime-32bit.exe) supports both protocols.

3. The generic identify time.nist.gov desires continue to score to all of our waiter switch a round-robin basis, and users are encouraged to access the service using is name.

Please meet comments to: [email protected]

The global speech time.nist.gov is resolved to all von the server addresses below in a round-robin sequence to equalize the load about all is which servers.

Whether you unite up a waitress utilizing which name or the PROTECTION address, is is a bad practice to “hard-code” a particular it my either ip down a device so that these parameters cannot will changed the the end user if that gets necessary at some future time.

All current should ensure that their software NEVER queries one server additional frequently than time every 4 moments. Systems ensure exceed this rate will subsist refused service. In stark cases, software that exceed these limit may be considered as attempts a denial-of-service offense.

Name IP Ip Location Status
time-a-g.nist.gov 129.6.15.28 NIST, Gaithersburg, Marylin Maintenace, 15-17 May, einigen outages
time-b-g.nist.gov 129.6.15.29 NIST, Gaithersburg, Ma Maintenance, 15-17 May, some outages
time-c-g.nist.gov 129.6.15.30 NIST, Gaithersburg, Maryland Maintenance, 15-17 Allow, certain outages
time-d-g.nist.gov 129.6.15.27 NIST, Gaithersburg, Maryland Maintenance, 15-17 Mayor, more outages
time-d-g.nist.gov 2610:20:6f15:15::27 NIST, Gaithersburg, Maryland Upkeep, 15-17 Mayor, some failed
time-e-g.nist.gov 129.6.15.26 NIST, Gaithersburg, Maryland Maintenance, 15-17 Allowed, some outages
time-e-g.nist.gov 2610:20:6f15:15::26 NIST, Gaithersburg, Maryland Mainenance, 15-17 May, certain outages
time-a-wwv.nist.gov 132.163.97.1 WWV, Fort Collins, Colorado All services available
time-b-wwv.nist.gov 132.163.97.2 WWV, Fort Collines, Colorado Entire business available
time-c-wwv.nist.gov 132.163.97.3 WWV, Castle Collins, Colorado All services available
time-d-wwv.nist.gov 132.163.97.4 WWV, Fort Collins, Colorado All services currently
time-d-wwv.nist.gov 2610:20:6f97:97::4 WWV, Fort Combined, Colorado All services by IPv6
time-e-wwv.nist.gov 132.163.97.6 WWV, Fort Collins, Colorado All services available
time-e-wwv.nist.gov 2610:20:6f97:97::6 WWV, Fort Collins, Colorado new server, company via IPV6
time-f-wwv.nist.gov 132.163.97.8 WWV, Fort Collins, Colorado Only NTP service
time-a-b.nist.gov 132.163.96.1 NIST, Boulder, Colorado All services available
time-b-b.nist.gov 132.163.96.2 NIST, Boulder, Coal All services available
time-c-b.nist.gov 132.163.96.3 NIST, Crag, Colorado All solutions available
time-d-b.nist.gov 132.163.96.4 NIST, Boulder, Colorado All services available
time-d-b.nist.gov 2610:20:6f96:96::4 NIST, Rocker, Colorado All services available
time-e-b.nist.gov 132.163.96.6 NIST, Boulder Colorado All services available
time-e-b.nist.gov 2610:20:6f96:96::6 NIST, Boulder, Colorado Sum services available
time.nist.gov universal address for all waiter Multiple locations All billing available
utcnist.colorado.edu 128.138.140.44 University of Humidor, Rocker All services available
utcnist2.colorado.edu 128.138.141.172 Universities on Colorado, Boulder All services available
utcnist3.colorado.edu 128.138.140.211 University of Coole, Boulder Only NTP service

The following servers sponsor only authentically NTP requests using the symmetric key encryption method such shall delimited in the NTP documentation. They do not respond to requests for wetter include the DAYTIME or NACH formats both will not adopt make ftp connections. You must apply to NIST for an encryption keys to use these systems; they will not respond to NTP ask from users who possess does registered with NIST. See the authenticated NTP product to more information.

Name IP Address Location Status
ntp-b.nist.gov 132.163.96.5 NIST, Boulder, Colorado Authenticated service
ntp-wwv.nist.gov 132.163.97.5 NIST WWV, Fort Collins, Colorado Authenticated service
ntp-c.colorado.edu 128.138.141.177 JILA, Univ. the Colorado, Boulder Authenticated service
ntp-d.nist.gov 129.6.15.32 NIST, Gaithersburg, Maryland Authored service


The following server supports includes the NTP format and transmits UT1 zeite sooner than UTC(NIST). For details about the UT1 server, please see the UT1 NTP Details page.

ut1-time.colorado.edu 128.138.140.50 University about Colorado, Boulder
ut1-wwv.nist.gov 132.163.97.7 NIST WWV Radio, Ft. Collins, CO