[ntp:questions] NTP-Question about "ntpq -p"
Richard B. Gilbert
rgilbert88 at comcast.net
Fri Aug 29 13:14:50 UTC 2008
> manuel.beicht at gmx.de (Manuel Beicht) writes:
>> I have some questions regarding synchronization and the output of "ntpq -p".
>> For example what is the significance of the "*" for example when you run ntpq
>> -p. Is this star a must because I have seen the polling sometimes and the time
>> mostly accurate but the "*" is missing. So does the server have to have a "*"
>> to be synched? In ntp documentation I read it just means that "*" denotes the
>> server that the NTP client is synching to but not necessarily that they are IN
>> synch. I am asking so far I considered any server without a "*" out of synch.
> Yes, * means it is the selected source. that ntp will slowly try to sync
>> Then I noticed the polling is dynamic but it seems to be too long with some
>> intervals and in particular too long when there is an offset. For example if
>> we have an offset of 1000 the polling is at 128 or at 256 instead of 64 or a
> If you have an offset of 1000 ntp will carry out a step when it decides
> that that is a genuine (ie, that the minimum offset recorded during 8
> polling intervals) offset.
> If you have an offset of 1000 something is very wrong with your network
> connection or your system.
Unless he introduced the error deliberately in order to "test" NTP.
>> lower level which I think would be more logical. There are actually some posts
>> on the ntp support sites that mention using custom polling parameters based on
>> the offset and latency ect...that do polling at 10 min 15 max and there is
>> some type of algorithm to find a match for anyone site.
> It is slow to decrease the poll interval.
>> Also what is acceptable offset and jitter? We currently experience 20-40ms
>> offset and 20-30ms jitter. sometimes it is up to 100-120ms offset.
> That is unusual. What kind of network connection do you have? A telephone
> modem connection? For a high speed connection, the usual offset is in the
> 10s of microsecond range for a local server, and 100s of microseconds for a
> relatively local machine. Even half way across the continent with a delay
> of 45ms, the offset is 100s of microseconds.
>> Is that still ok? What is the acceptable range usually?
>> I would be very glad if you could provide me with some help.
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