[ntp:questions] RE: How to change STRATUM on linux.

Danny Mayer mayer at ntp.isc.org
Sat Oct 21 02:19:15 UTC 2006


David Woolley wrote:
> Two is a bad number, as, if they disagree, you can't resolve the
> dispute.  Having two local clocks in a system, unless one is slave
> to the other, is a very bad idea.
> 
>>   address         ref clock     st  when  poll reach  delay  offset disp
>> *~x.x.x.x      127.127.1.0       6   373  1024  377     3.1    0.28 0.3
>>  ~x.x.x.x      127.127.1.0       8  1012  1024  377     2.4  -760.9 103.9
> 
> If it weren't being rejected on stratum, the lack of overlap in the
> error bands between the second and first source would, I believe, 
> cause both sources to be rejected as false tickers.  It's faintly
> possible to have this amount of offset difference between two remote
> servers, but these servers will be indicating very tight error bounds.
> Unfortunately, when you use the local clock driver to propagate time
> that has been synchronised by non-NTP means, it fails to send the correct
> error information, although, in this case, if it had done, the Cisco should
> have rejected it for having too high a root dispersion.
> 

This is even worse than having no time at all. The upstream servers are
only synchronized to themselves, ie not at all, which is what those
refids are telling you. They have no reference which will allow them to
stay in synch, even loosely. You are better of synchronizing to just one
of these, but even better to some real server that are providing proper
time.

Danny




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