[ntp:questions] offset with ntpdate and ntpq ?

Unruh unruh-spam at physics.ubc.ca
Mon Sep 1 05:11:54 UTC 2008

David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:

>Stavros Milos wrote:

>> I would like to "read" a time of each remote NTP server and compare it 
>> to my local referential timeserver, just to examine if offset of each 
>> remote NTP server is not too high. So, the purpose is not to synchronize 
>> time to remote NTP servers, but to trace their time to keep a rule:
>>   "remopte NTP server time" - "my referential NTP server time"  <  0.5s

>"Offset" doesn't really give you this information.  If the ntpd design 
>is valid, "offset" is either a measure of the network performance, or 
>that ntpd has not been running long enough to work out which part of the 
>offset is a true clock error and which part measurement variation.  If 
>you know of a way of telling the difference between a true error and 
>measurement uncertainty, before ntpd is able to do so, you need to 
>submit your algorithm to the NTP community.

Actually I have submitted such an algorithm but interest is low ( chrony
does it much faster than does ntp) But that is irrelevant. If he has
network errors of 500ms he has one very very weird network. For a local
network the network errors are typically microseconds, not seconds. ( Note
that offsets of seconds ntp will step so apparently it does know it is not
random network errors. )

More information about the questions mailing list