[ntp:questions] Re: NTP sync problems

David L. Mills mills at udel.edu
Thu Dec 16 14:46:53 UTC 2004


There might be some misconception here. The mitigation algorithm 
establishes a bound on the offset of any server with respect to 
roundtrip delay and dispersion. This is a matter of physics and theory. 
When multiple servers are involved, the algorithm computes an 
intersection interval within which the server clocks can be considered 
valid. A possibly correct time must be contained in this intersection. 
If the intersection is empty, a correct time cannot be established. This 
is independent of the stratum.


Terje Mathisen wrote:
> Brad Knowles wrote:
>> At 12:43 PM -0600 2004-12-15, Robert Rati wrote:
>>>                         This is what spurred my original question which
>>>  was, shouldn't NTP sync to the server(s) with the lower stratum
>>>  regardless of how different the time is that is being served from
>>>  higher stratum servers?
>>     Because this is not the way the NTP algorithms were designed to 
>> work.  If you want to use just one time server to which everyone 
>> syncs, that should work -- until such time as the primary goes down or 
>> is unreachable.
> Right.
> If you then wants a secondary, higher-stratum, server as backup, said 
> server should be configured to also be a client of the primary server.
> That way they will agree as long as both are up, and if the primary goes 
> away, the secondary server will start out with the same time, drop down 
> a few stratum levels, but still server time.
> Terje

More information about the questions mailing list