Re: portable atomic clocks

From: Mark A. Haun (
Date: Thu Jan 18 2001 - 09:42:51 PST

  • Next message: suhas: "Re: portable atomic clocks"

    I'm surprised that nobody so far has mentioned NTP.  The Network Time
    Protocol is an Internet standard for clock synchronization (defined in RFC
    1305 and RFC 2030, if you're into such things).  In fact, NTP as an Internet
    application pre-dates the world wide web by many years!  Rather than just
    setting your computer at regular intervals to some master clock, it
    maintains hierarchies/graphs of time servers and clients on the network and
    keeps good synchronization among them all by estimating the packet travel
    times between hosts.
    Everything you ever wanted to know about NTP can be found at
    I understand that there is a limited implementation of NTP built into
    Windows 2000, and a version of the software may be available for NT as well. 
    Otherwise, if you're fortunate enough to use some flavor of UNIX, you can
    build the standard client software from the sources found at the above site. 
    Some distributions of Linux offer NTP in package form (I use Debian).
    The software runs in the background, uses very little memory, CPU, or
    network bandwidth, and makes sure the clock is always right.  In my case the
    accuracy is about one millisecond.  This whole scheme assumes that you have
    an "always on" connection to the Internet, but nowadays that is becoming
    fairly common.
    Mark Haun
    University of Illinois, Dept. of ECE
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    This archive was generated by hypermail 2b29 : Thu Jan 18 2001 - 09:43:03 PST