[ntp:questions] Offset is always increasing

Riccardo Castellani ric.castellani at alice.it
Wed May 22 08:38:36 UTC 2013


I thank you very much for your precious answer but I'm very happy to know my 
configuration is good ;)

>> Do this. Disable NTP on FORCLIENTS, then run ntpdate every minute (cron 
>> would be good here) with "-q" and "-s". You will probably see an 
>> increasing offset.
With this command, I will save 'offset' value but without adjusting the 
local clock, it's right ?

>>Check to see if it is monotonically increasing. If it occasionally resets 
>>or goes backward, then you probably have resync to TOD chip and that may 
>>be part of the problem.
What means to resync TOD chip ?! To replace hardware clock ?! How is it 
possible to resync !? In HP-UX I know 'date' command sets both the hardware 
clock and the system clock.
My hardware is blade HP BL860c with 2 CPU, where each one is DualCore Intel 
Itanium 2 - 1666 MHz.

>> Otherwise, take the offset at the end and subtract the offset at the 
>> beginning then divide by the time between the start and the end. That 
>> will give you the drift rate.
This one represents the average of drift rate about my hardware clock ? It's 
all right ?
How long this cron task do you suggest to run to be meaningful ? 30 minutes 
?

>>> If that rate is larger than 500 parts per million, then NTP cannot 
>>> correct the clock.
Acoording test you suggested me by 'ntpdate', if this drift average is 
bigger 500 ppm ... ntpd cannot adjust local clock, where can I find 
documents to find out reason ?
I don't know if it's can be useful but now 'drift rate' value, which ntpd 
saves automatically in its file, is about 855 !
My local clock overstepped 10 minutes forward, I don't understand because 
clock was not adjusted step by step without to collect over 10 minutes !
How do you know where I can find info about it ?

thanks again




----- Original Message ----- 
From: "Brian Utterback" <brian.utterback at oracle.com>
To: <questions at lists.ntp.org>
Sent: Tuesday, May 21, 2013 3:02 PM
Subject: Re: [ntp:questions] Offset is always increasing


> FORCLIENTS clock has a huge frequency problem, way beyond what NTP can 
> correct.
>
> Do this. Disable NTP on FORCLIENTS, then run ntpdate every minute (cron 
> would be good here) with "-q" and "-s". You will probably see an 
> increasing offset. Check to see if it is monotonically increasing. If it 
> occasionally resets or goes backward, then you probably have resync to TOD 
> chip and that may be part of the problem. Otherwise, take the offset at 
> the end and subtract the offset at the beginning then divide by the time 
> between the start and the end. That will give you the drift rate. If that 
> rate is larger than 500 parts per million, then NTP cannot correct the 
> clock.
>
> On 05/21/13 07:57, Riccardo Castellani wrote:
>> I'm using n. 1 ntp server (XNTPD daemon on HP-UX, called FORCLIENTS,
>>
>> 192.168.1.240) for my clients and I'm obtaining the message
>> "synchronization
>> lost" about every 20 minutes.
>> Source time is another server (MASTER) on my lan
>> which updates its time
>> directly from Internet servers.
>>
>>
>> MASTER is OK
>>
>> FORCLIENTS has a high offset !
>>
>>
>> ntp.conf of FORCLIENTS (192.168.1.240):
>>
>>
>> restrict default ignore
>> server 10.2.3.5
>> driftfile /etc/ntp.drift
>> restrict
>> 127.0.0.1
>> restrict 127.127.1.1
>> restrict 10.2.3.5
>> restrict 192.168.1.240
>>
>> restrict 192.168.0.0 mask 255.255.0.0 nomodify noquery
>> server 127.127.1.1
>> fudge
>> 127.127.1.1 stratum 10 # show poor quality
>>
>>
>>
>> ntp.conf of MASTER (10.2.3.5):
>>
>>
>> restrict default ignore
>> restrict 127.0.0.1
>> restrict 192.168.1.240 mask
>> 255.255.255.255 nomodify
>> restrict ntp1.inrim.it mask 255.255.255.255 nomodify
>> noquery notrap nopeer
>> restrict ntp2.inrim.it mask 255.255.255.255 nomodify
>> noquery notrap nopeer
>> restrict ntp1.fau.de mask 255.255.255.255 nomodify
>> noquery notrap nopeer
>> restrict ntp2.nl.net mask 255.255.255.255 nomodify
>> noquery notrap nopeer
>> restrict 127.127.1.0 mask 255.255.255.255
>> server ntp1.
>> inrim.it
>> server ntp2.inrim.it
>> server ntp1.fau.de
>> server ntp2.nl.net
>> server
>> 127.127.1.0
>> fudge 127.127.1.0
>> driftfile /var/lib/ntp/drift
>>
>>
>>
>>
>>
>>
>>
>> My server log
>> shows:
>>
>>
>> 20 May 14:38:20 xntpd[19386]: synchronized to LOCAL(1), stratum=10
>> 20
>> May 14:39:23 xntpd[19386]: synchronized to 10.2.3.5, stratum=2
>> 20 May 14:54:18
>> xntpd[19386]: time reset (step) -1.014343 s
>> 20 May 14:54:18 xntpd[19386]:
>> synchronisation lost
>> 20 May 14:58:35 xntpd[19386]: synchronized to LOCAL(1),
>> stratum=10
>> 20 May 14:59:38 xntpd[19386]: synchronized to 10.2.3.5, stratum=2
>> 20
>> May 15:14:33 xntpd[19386]: time reset (step) -1.010761 s
>> 20 May 15:14:33 xntpd
>> [19386]: synchronisation lost
>> 20 May 15:16:08 xntpd[13208]: logging to file
>> /var/adm/syslog/ntp.log
>> 20 May 15:16:08 xntpd[13208]: tickadj = 625, tick =
>> 10000, tvu_maxslew =
>> 61875
>> 20 May 15:16:08 xntpd[13208]: precision = 6 usec
>> 20
>> May 15:17:29 xntpd[14031]: logging to file /var/adm/syslog/ntp.log
>> 20 May 15:17:
>> 29 xntpd[14031]: tickadj = 625, tick = 10000, tvu_maxslew =
>> 61875
>> 20 May 15:17:
>> 29 xntpd[14031]: precision = 10 usec
>> 20 May 15:21:46 xntpd[14031]: synchronized
>> to 10.2.3.5, stratum=2
>> 20 May 15:21:46 xntpd[14031]: time reset (step)
>> -0.216182 s
>> 20 May 15:21:46 xntpd[14031]: synchronisation lost
>> 20 May 15:26:03
>> xntpd[14031]: synchronized to LOCAL(1), stratum=10
>> 20 May 15:27:06 xntpd
>> [14031]: synchronized to 10.2.3.5, stratum=2
>> 20 May 15:42:01 xntpd[14031]: time
>> reset (step) -1.005840 s
>> 20 May 15:42:01 xntpd[14031]: synchronisation lost
>> 20
>> May 15:46:18 xntpd[14031]: synchronized to LOCAL(1), stratum=10
>> 20 May 15:47:21
>> xntpd[14031]: synchronized to 10.2.3.5, stratum=2
>> 20 May 16:02:16 xntpd[14031]:
>> time reset (step) -1.009925 s
>> 20 May 16:02:16 xntpd[14031]: synchronisation
>> lost
>> 20 May 16:06:33 xntpd[14031]: synchronized to LOCAL(1), stratum=10
>> 20 May
>> 16:07:36 xntpd[14031]: synchronized to 10.2.3.5, stratum=2
>>
>>
>>
>> nptd -qn shows:
>>
>>
>>
>>
>> remote refid st t when poll reach delay offset
>> disp
>>
>> ============================================================================
>> ==
>>
>> 10.2.3.5 193.204.114.232 2 u 16 64 7 1.92 -158.96 3927.72
>> 127.127.1.1
>> 127.127.1.1 10 l 15 64 17 0.00 0.000
>> 1885.01
>>
>>
>>
>> My time source server is ok
>> (10.2.3.5) and I can exclude problems into my
>> lan.
>>
>>
>>
>> remote local st poll
>> reach delay offset disp
>>
>> =======================================================================
>> =ntp1.
>> nl.uu.net 10.2.3.5 1 1024 377 0.04411 -0.003625 0.12183
>> =ntp1.inrim.it 10.2.3.5
>> 1 1024 377 0.01971 -0.000409 0.12172
>> *ntp2.inrim.it 10.2.3.5 1 1024 377 0.01923
>> -0.000046 0.12175
>> =LOCAL(0) 127.0.0.1 10 64 377 0.00000 0.000000 0.03072
>> =ntp1.
>> rrze.uni-e 10.2.3.5 1 1024 377 0.05191 -0.009084 0.12178
>>
>>
>>
>>
>>
>> Can you indicate
>> suggestions please ? The problem is Offset bigger 128 ms
>> ?!?! Offset is
>> increasing until to 700-800 ms.
>>
>> I run ntpdate to update immediately clock and
>> I can see small offset but
>> after few minutes grows again until to exceed 128
>> ms.
>>
>> How can I solve it ?
>> _______________________________________________
>> questions mailing list
>> questions at lists.ntp.org
>> http://lists.ntp.org/listinfo/questions
>
>
> -- 
> blu
>
> Always code as if the guy who ends up maintaining your code will be a
> violent psychopath who knows where you live. - Martin Golding
> -----------------------------------------------------------------------|
> Brian Utterback - Solaris RPE, Oracle Corporation.
> Ph:603-262-3916, Em:brian.utterback at oracle.com
>
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