USNO NTP NETWORK TIME SERVERS


The Naval Observatory operates an ensemble of stratum 1 NTP servers which are synchronized to the USNO Master Clocks or to GPS as their stratum 0 reference clocks.

Network Time Protocol (NTP) is an Internet standard protocol which enables client computers to maintain system time synchronization to the US Naval Observatory Master Clocks in Washington, DC and Colorado Springs, CO.

NTP runs as a client program on a computer. It sends periodic time requests to one or more servers, obtaining server time stamps and using them to adjust the client's clock.

Typical accuracy achieved is in the range 1 - 30 ms continuous, and is highly dependent on the symmetry and speed of the Internet path between client and server. Best results are achieved using a combination of servers which are closest to the client in a network sense.

To obtain precise time from USNO NTP servers, follow these procedures:
1. Download NTP client software from ntp.org.
2. Select one or more NTP servers and add to your client configuration.
3. Run the NTP client on your machine. We request that you allow no more than three of your clients to poll our servers directly. Organizations with many clients should obtain time from local stratum 2 servers. ISPs should configure routers or firewalls to serve as stratum 2 servers to the ISP network. Dialin clients should contact your ISP for information about NTP services.

All of the following stratum 1 NTP servers are open to stratum 2 servers within the same time zone and to others by arrangement. Individual users should consult the public list of stratum 2 servers.

Please note that these servers support only Network Time Protocol (Internet RFC-1305a) and Simple Network Time Protocol (SNTP).

DoD NIPRNET ONLY

  • ntp.usno.navy.mil (192.5.41.42)
    Synchronization: NTP V4 primary (USNO Master Clock H-masers )
    Location: Time Service Dept., U.S. Naval Observatory, Washington, DC
    Access Policy: open access for DoD NIPRNET only. No public access.
    This is the recommended NTP server for NIPRNET clients.

    U.S. EASTERN TIME ZONE

  • tick.usno.navy.mil
    Location: Time Service Dept., U.S. Naval Observatory, Washington, DC
    Synchronization: NTP V4 primary (USNO Master Clock H-masers)
    Access Policy: open access for MIL, GOV, and other stratum 2 servers.
    Note, USNO operates three NTP servers as part of an IP load-balanced farm to handle high traffic.

  • ntp-s1.cise.ufl.edu
    Location: University of Florida, Gainesville, FL
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and UFL clients,others by arrangement

  • ntp.colby.edu
    Location: Colby College, Waterville, ME
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and Colby clients,others by arrangement

  • navobs1.oar.net
    Location: OARnet, Ohio State University, Columbus, Ohio
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and OARnet, others by arrangement

  • gnomon.cc.columbia.edu
    Location: Columbia University, New York City
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and CU, others by arrangement

  • tick.gatech.edu
    Location: Georgia Institute of Technology, Atlanta, Georgia
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and GATECH clients, others by arrangement

  • navobs1.mit.edu
    Location: Massachusetts Institute of Technology, Cambridge, MA
    Synchronization: NTP V4 primary
    Access Policy: This server is no longer in operation.

    U.S. CENTRAL TIME ZONE

  • ntp.okstate.edu
    Location: Oklahoma State University, Stillwater, OK
    Synchronization: NTP V4 primary
    Access Policy: open access for Central and neighboring time zones, others by arrangement

  • navobs1.wustl.edu
    Location: Washington University, St. Louis, Missouri
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and WUSTL, others by arrangement

  • tick.uh.edu
    Location: University of Houston, Houston, Texas
    Access Policy: open access for stratum 2 servers and UH, others by arrangement

    U.S. MOUNTAIN TIME ZONE

  • tick.usnogps.navy.mil
    Location: US Naval Observatory Alternate Master Clock, Colorado Springs, CO
    Synchronization: NTP V4 primary (USNO Master Clock H-masers)
    Access Policy: open access for MIL, GOV, and stratum 2 servers, others by arrangement

  • tock.usnogps.navy.mil
    Location: US Naval Observatory Alternate Master Clock, Colorado Springs, CO
    Synchronization: NTP V4 primary (USNO Master Clock H-masers)
    Access Policy: open access for MIL, GOV, and stratum 2 servers, others by arrangement

    U.S. PACIFIC TIME ZONE

  • montpelier.caltech.edu
    Location: California Institute of Technology, Pasadena, CA
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and Caltech clients, others by arrangement

  • bigben.cac.washington.edu
    Location: University of Washington, Seattle, Washington
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and UW clients, others by arrangement

  • tick.ucla.edu
    Location: University of California, Los Angeles
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and UCLA clients; others by arrangement

  • usno.pa-x.dec.com
    Location: Compaq Corporation, Palo Alto, CA
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers, Compaq, others by arrangement

    ALASKA TIME ZONE

  • ntp.alaska.edu
    Location: University of Alaska, Fairbanks, AK
    Access Policy: open access for stratum 2 servers and UAF, others by arrangement

    HAWAII TIME ZONE

  • tick.mhpcc.hpc.mil
    Location: Maui High Performance Computing Center, Maui, Hawaii
    Longitude: 156 26.4070 W
    Latitude: 20 44.9286 N WGS84
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and MHPCC, others by arrangement

    SECRET INTERNET PROTOCOL ROUTING NETWORK

  • ntp-usno.sipr.smil.mil
    Location: USNO Time Service, Washington, DC
    Synchronization: NTP V4 primary (USNO Master Clocks 1,2)
    Access Policy: open access for SIPRnet clients

  • ntp-amc.sipr.smil.mil
    Location: USNO Alternate Master Clock Facility, Shriever AFB, Colorado
    Synchronization: NTP V4 primary (USNO Master Clocks 1,2)
    Access Policy: open access for SIPRnet clients

    WE STRONGLY RECOMMEND THAT YOU CHOOSE ONE OR MORE SERVERS CLOSE TO YOU, AND IN ADDITION SELECT OTHER SERVERS FOR REDUNDANCY.

    For further information contact Time Service Dept., USNO
    Jeff Prillaman (jeffrey.prillaman@usno.navy.mil)

    Back to Time Service Home Page
    "The inaudible and noiseless foot of Time." --W. S.