[ntp:questions] Re: Can NTP get permanently confused?

David L. Mills mills at udel.edu
Sun Oct 2 01:02:57 UTC 2005


Be advised NTPv3 (xntp) does in fact display a different time from the 
actual computer time while the clock adjustment is being amortized. This 
was one of the factors that led to the development of NTPv4 (ntpd). he 
xntpd had two timescales, one for daemon and the other for the computer 
clock. The difference is not much under most circumstances, so if you 
are not concerned about crashing an airplane, just ignore it.


Richard B. Gilbert wrote:
> olssons at gmail.com wrote:
>> I have found that if I set the clock by 2 seconds on my NTP server that
>> the NTP clients seem to get confused.  First they notice the time jump
>> and unsynchronize with the time server.  About 10-20minutes later, they
>> resynchronize with the NTP server and all appears well, but if I then
>> go and verify the actual time on the NTP server and clients, the
>> clients are still showing 2 seconds ahead of the NTP server.
>> ntpq -p shows a 0 or near 0 (.9 milliseconds) offset between the
>> clients and the NTP server during this time.
>> The clients never recover unless I stop NTP, do an ntpdate, and restart
>> NTP.  Is this normal behavior?
>> FYI, clients are both Tru64 and SunOS versions of xntpd.
>> Network Time Server - Symmetricom/TrueTime NTS-100 NTP Server
>> System OS - Tru64 UNIX 4.0F , SUNOS 5.6
>> NTP Version - xntpd 3-5.93e
> xntpd 3-5.93e is a truly antique version of ntpd.   It's so old that 
> even the Smithsonian doesn't want it.
> The current version is v4.2.0, soon to be 4.2.1.    You are missing 
> seven or eight years of fixes and enhancements!
> The reference implementation builds nicely on Solaris 8 and 9 and runs 
> quite well.  You can get a pre built version for Solaris from 
> sunfreeware.com or blastwave.org.  It should be available for at least 
> Solaris 7, 8, 9 and 10.  Or you can download the source for the current 
> version of the reference implementation from
> http://ntp.isc.org/bin/view/Main/SoftwareDownloads

More information about the questions mailing list