[ntp:questions] Win7: ntpd adjusting time backwards

Jeroen Mostert jmostert at xs4all.nl
Mon Dec 10 22:13:09 UTC 2012


On 2012-12-10 22:54, unruh wrote:
> On 2012-12-10, Jeroen Mostert<jmostert at xs4all.nl>  wrote:
>> On 2012-12-10 22:18, David Woolley wrote:
>>> Jeroen Mostert wrote:
>>>
>>>>>
>>>> For what it's worth, after all of that, the offset is steadily zigzagging
>>>> between 27 and 41 ms, which I'm guessing is about the best you can hope for on
>>>> a Windows machine with Internet sync. There have not been any major time step
>>>> adjustments.
>>>
>>> Offsets should be scattered around zero. If they are all the same sign,
>>> something is wrong.
>>
>> OK. Well, that's too bad, I guess.
>>
>> Throw me a bone here, fellas. It's nice to know something is wrong, but if all I
>> can see is that all peers consistently report offsets in this range, the best I
>> can conclude is that either ntpd simply isn't successful in disciplining the
>> clock appropriately, or there is some network problem going on that someone who
>> understands the NTP protocol could probably diagnose. That someone would not yet
>> be me.
>>
>> If I offset the offsets (pardon my math) by -33 milliseconds, I'd roughly have a
>> zero axis that they'd be swinging around with a range of -10/+10. According to
>> unruh, even that would still be horrible in terms of accuracy, so I'm not sure
>> if that's fair in its simplicity.
>>
> Ah, if it really is 33 ms off on average, then yes something is wrong.
> I assumed that you meant that the width of the scatter was 27-41ms, not
> that the actual offset was always one sign and that far off.
>
> However I do have to ask what this offset is.
> What are your server entries in ntp.conf?

pool nl.pool.ntp.org iburst

> Is this offset the offset from the same server that is being used to set the
> time? Maybe a few lines from /var/log/ntp/peerstats.xxxxxxx would let us see
> what the offset was doing. Or using some of the plotting programs to plot the
> offsets measured from the varios servers.
>
ntpq -np:

      remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
  nl.pool.ntp.org .POOL.          16 p    -   64    0    0.000    0.000   0.977
*213.136.0.252   .PPS.            1 u  800 1024  377   18.958   35.896  10.670
+213.239.154.12  193.190.230.65   2 u  572 1024  377   18.924   35.018   8.883
+81.171.44.131   193.190.230.66   2 u  528 1024  377   18.855   34.990   7.952
+46.19.33.5      193.79.237.14    2 u  381 1024  377   17.953   35.253   8.111
+95.211.111.53   221.238.121.188  3 u  674 1024  377   18.924   35.641   8.806
+195.191.113.251 193.79.237.14    2 u  694 1024  377   19.920   34.866   7.075
+178.251.121.16  193.67.79.202    2 u    7 1024  377   18.956   33.863   8.940
-83.98.201.133   153.60.75.10     2 u  703 1024  377   17.986   33.285   7.294
+192.87.106.2    192.87.106.3     2 u  484 1024  377   17.853   32.520   6.394


peerstats tail of today (cutting off the first column to prevent wrapping):

77050.630 46.19.33.5 1424 0.032273618 0.018946933 0.016009420 0.005895699
77422.629 178.251.121.16 141a 0.034412494 0.018950946 0.016068324 0.009463505
77724.626 213.136.0.252 161a 0.035895776 0.018958086 0.016099349 0.010622052
77792.626 83.98.201.133 133a 0.035527840 0.018976950 0.016341863 0.009205395
77925.626 213.239.154.12 141a 0.031416422 0.017919850 0.020178597 0.006312898
77982.626 81.171.44.131 143a 0.031503337 0.018806412 0.020621400 0.005369126
78106.626 46.19.33.5 1424 0.035252534 0.017952556 0.016150506 0.008054216
78867.627 83.98.201.133 133a 0.033285314 0.017985677 0.016441743 0.007294158
78876.629 195.191.113.251 143a 0.034866163 0.019920461 0.016225952 0.007074704
78896.628 95.211.111.53 1424 0.035640734 0.018924019 0.020330239 0.008805813
78998.630 213.239.154.12 141a 0.035017893 0.018924218 0.020397573 0.008882811
79042.628 81.171.44.131 143a 0.034990054 0.018854869 0.020404077 0.007952290
79086.627 192.87.106.2 141a 0.032519558 0.017852997 0.016296482 0.006394490
79563.628 178.251.121.16 141a 0.033863486 0.018955711 0.020809018 0.008940402

As far as I can tell the peer offsets are OK, if you just ignore the fact that 
they're all too high -- and stay that way.

-- 
J.



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