Network Time Protocol Server

CITES > techsupport > ntp

CITES provides Network Time Protocol (NTP) servers that can be used to synchronize the time of other computers on campus.

Configure your system to use ntp.uiuc.edu, which will resolve (randomly) to one of CITES' three Stratum-2 time providers. (Windows systems that are joined to a domain (e.g. UIUC) already synchronize their clocks to a domain controller, and should not be manually reconfigured to use the CITES NTP servers.)

NTP is not the same as timed; timed uses a different protocol which our time servers do not support. To use NTP with a Windows 98 machine, you will need third-party software; later Windows operating systems like NT 3 forward, 2000, and XP support NTP. Macintoshes also use NTP. Users who who have personal firewall software may need to adjust their firewall's configuration to enable communication with an NTP server. (More information is also available.)

The three Stratum-2 machines set their own clocks accurately by referring to the campus Stratum-1 time source, which keeps time within about 20 microseconds of true UTC using a GPS receiver. GPS, the Global Positioning System, allows precise location of receivers anywhere on earth, and to do this the receivers must know exactly what time it is relative to the GPS satellites, so a useful side effect of precise GPS positioning information is that the receiver also gets to find out the exact time.

If there are applications on systems on campus that require time accurate to the sub-millisecond level, direct NTP peering with the Stratum-1 clock can be arranged; however for the vast majority of systems on campus, the time from the Stratum-2's is more than sufficient, resulting in a clock setting within ten milliseconds or so of the exact time.

More information

If you're interested in general information on NTP, you can find an overview, history, and other interesting references at
http://www.eecis.udel.edu/~ntp/ntpfaq/NTP-a-faq.htm

For additional information about using NTP with Macintosh OS X, see
http://docs.info.apple.com/article.html?artnum=61273

For most versions of Windows, the command

net time /setsntp:ntp.uiuc.edu

will set your machine to synchronize with the CITES NTP servers. For additional information about NTP and various versions of Windows, see:

Windows XP
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/net_time.mspx?mfr=true

Windows 2000
http://www.microsoft.com/windows2000/docs/wintimeserv.doc

Windows NT
http://support.microsoft.com/?kbid=266209

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