On 2008-12-09, David Woolley <[EMAIL PROTECTED]> wrote: > Hushpuppy wrote: > >> At my work (financial services) the market rules mandate >> synchronizing our clocks to within a maximum 3 second difference >> of the NIST atomic clock. We also need to log/document that we are >> within 3 seconds. > > If ntpd is allowed to step and it has been more or less correct at > some time, you will not get such a large error unless something is > broken. If something is broken, it will invalidate the statistical > measurements, anyway.
NTP can easily keep your clock within 3000 milliseconds of UTC. Unless it is badly configured or the clock is broken. > However, I think the worst case is something like root delay / 2 > + root dispersion, plus last hop delay / 2, plus precision, + 15 > microseconds for every second since the time was updated. You're talking about calculating the synchronization distance (see RFC-1305). The ntptrace utility will do this for you. Root Dispersion is a 32-bit signed fixed-point number indicating the maximum error relative to the primary reference source, in seconds with fraction point between bits 15 and 16. Only positive values greater than zero are possible. RFC-1305 may be found at http://www.faqs.org/rfcs/rfc1305.html -- Steve Kostecke <[EMAIL PROTECTED]> NTP Public Services Project - http://support.ntp.org/ _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
