NTP Time Service

NTP (Network Time Protocol) provides highly accurate atomic time for individuals connected to the Internet. Caltech, in agreement with the United States Naval Observatory, has installed a NTP Stratum 1 server that uses GPS time for synchronization. This server is available for on campus as well as off campus public use.

Recently, Caltech purchased several Stratum 1 time servers for internal and external use using various methods for calculating time. These new time servers are being deployed as time and infrastructure allow. These new servers are used by Caltech to provide NTP to servers, network devices and other services requiring accurate time information.

What are the Server Addresses?

NTP Server Name Server IP Address NTP Server Method Status
ntp-01.caltech.edu L1 C/A Code GPS, using TCXO Deployed
ntp-02.caltech.edu CDMA using TCXO and OCXO, proprietary Linux Kernel Deployed
ntp-03.caltech.edu L1 C/A Code GPS, using TCXO Offline
ntp-04.caltech.edu L1 C/A Code GPS, SPS GPS, TCXO Offline

On Campus

If you are on campus, we have configured our routers to relay this information to your local subnet. If you are using NTP client software which requires you to configure it (your computer is not using DHCP or your computer cannot automatically configure the NTP settings), please use the local router address (for example 131.215.xxx.254). This is a feature of the network equipment we have installed on campus and does not require your NTP client to calculate the number of hops when determining true time.

Off Campus

USNO lists access to the NTP Server at Caltech as:

Service area: USA Pacific timezone, others by arrangement
Access Policy: open access for stratum 2 servers

This means that you are free to configure your NTP client to use this server for time information. You don't normally need premission to use this server, it is freely availble for public use. This server will only peer with other USNO servers and will not accept peering requests for other hosts. This should not cause any problems for those using clients to obtain NTP time from this server.

If your computer is located off campus, please use the address ntp-01.caltech.edu where your NTP client asks for the NTP host. We have placed this computer as close as we can to the "outside world" to provide the least number of hops to off-campus sites. If your software requires the IP address be used, please use

If you are associated with Caltech and travel with a notebook computer (or have a computer that you use in on and off campus locations), NTP is tolerant to your computer being moved and will calculate the correct time for you. If you use any of the Caltech specific addresses and are off campus, those addresses will still work properly. If you leave Caltech (graduate, leave, retire), please configure your NTP client to use the Off Campus address.

If you have questions, contact us at http://help.caltech.edu (request type IMSS-->Network, Wireless & Remote Access-->Other)

For additional information regarding NTP clients or the NTP Protocol, please visit http://www.ntp.org.