[ntp:questions] NTPD silently not tracking

unruh unruh at invalid.ca
Tue Sep 3 04:35:45 UTC 2013

On 2013-09-03, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> On 09/02/2013 02:33 PM, David Lord wrote:
>> Harlan Stenn wrote:
>>> David Lord writes:
>>>> Magnus Danielson wrote:
>>>>> server ntp1.kth.se iburst maxpoll 7
>>>>> server ntp2.kth.se iburst maxpoll 7
>>>>> server ntp3.kth.se iburst maxpoll 7
>>>>> server ntp1.sp.se iburst maxpoll 7
>>>>> server ntp2.sp.se iburst maxpoll 7
>>>> that seems too restrictive and possibly abusive if you do not
>>>> yourself have control over those servers.
>>> iburst is not abusive.
>>> Perhaps you are thinking of burst?
>> I was thinking about maxpoll 7 and the few stats that were
>> given indicating the very poor reach for the configured
>> servers.
> There is good network connectivity to all 5 servers.
> If you advice us not to use maxpoll 7, then we naturally will learn from
> it. I don't use it personally, but I didn't set this machine up. Would
> be nice to hear your explanation thought.

Being nice to the people who are freely providing you with a resource.
Think of 10,000,000 other machines all behaving in the same way ( and
for a "major stratum 1 server" that can quite possibly be the case. Then
100,000 queries per second or 10000 queries per second can make a big

Of course if it is your own server, then none of the above applies and
you could do maxpoll 4 if you wished. 

> However, when doing the ntpdc peers command (in interactive mode), it
> had all 5 servers available, and was tracking one (as indicated with =
> and * at the beginning of the lines, I was told this over phone, so I
> don't have visual memory of it all). So, I don't think bad connectivity
> was the cause. It looked to a non-NTP expert like it had peers, was
> happy with offsets (albeit it looked unexpectedly good at 0) but just
> was plain way off in time.  It took multiples querries with ntpdc peers
> before it reacted on the time-offset, started to display big offsets and
> eventually clean up itself. ntpdate -q did expose the time error of 6 days.

Do you have the logs? Can you see it drifting off time? Can yousee the
offsets getting bigger and bigger? It is really really hard to imagine a
6 day offset to accumulate over a time scale of less than 1000 years.
for any resonable computer clock. 

> Cheers,
> Magnus

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