[ntp:questions] Network problems affecting NTP

David Woolley david at ex.djwhome.demon.invalid
Fri Jul 1 20:44:36 UTC 2011


Eugen COCA wrote:
> Due to a network problem on our provider, the packets were routed on a

Duplicate thread.

> different path than usual yesterday, for several hours. This period,
> NTP displayed wrong offsets:
> 
> +GPS_NMEA(1)     .GPS.            0 l   16   16  377    0.000
> 0.001   0.002
>  ptbtime1.ptb.de .PTB.            1 u    4   64  377   64.545
> -4.450   0.140
>  ntps1-1.cs.tu-b .PPS.            1 u   49   64  357   65.944
> -4.335   0.223
>  ntp-p1.obspm.fr .TS-2.           1 u   27   64  377   68.793
> -4.233   0.034
>  GPS-1.MIT.EDU   .GPS.            1 u   53   64  377  155.543
> -4.491   1.779
> oPPS(1)          .PPS.            0 l    9   16  377    0.000
> 0.001   0.002
>  ntp1.usv.ro     .PPS.            1 u   14   64  377    0.290
> 0.016   0.006
>  ntp2.usv.ro     .PPS.            1 u    4   64  377    0.229
> 0.017   0.027
>  ntp3.usv.ro     .PPS.            1 u    5   64  377    0.269
> 0.023   0.026
> -ptbtime2.ptb.de .PTB.            1 u   51   64  277   64.426
> -4.276   0.190
> -ntp0.rrze.uni-e .GPS.            1 u   29   64  377   55.088
> -4.486   0.039
> +ntp1.oma.be     .PPS.            1 u   64   64  377   63.900
> -4.257   0.509
> -time-a.nist.gov .ACTS.           1 u   11   64  373  204.117
> 16.101  49.841
> 
> After the problem was solved, the packets were routed on the usual
> path. The result is:
> 
> +GPS_NMEA(1)     .GPS.            0 l   35   64  377    0.000
> 0.001   0.002
>  ptbtime1.ptb.de .PTB.            1 u   48  256  377   49.194
> -0.021   0.265
>  ntps1-1.cs.tu-b .PPS.            1 u   69  256  377   50.778
> -0.044   0.675
>  ntp-p1.obspm.fr .TS-2.           1 u   15  256  377   53.307
> 0.242   0.047
>  GPS-1.MIT.EDU   .GPS.            1 u   95  256  377  140.137
> -0.414   0.637
> oPPS(1)          .PPS.            0 l    4   16  377    0.000
> 0.001   0.002
>  ntp1.usv.ro     .PPS.            1 u   31   64  377    0.198
> 0.000   0.003
>  ntp3.usv.ro     .PPS.            1 u   50   64  377    0.175
> -0.002   0.004
>  ntp4.usv.ro     .PPS.            1 u   56   64  377    0.198
> -0.020   0.005
>  ptbtime2.ptb.de .PTB.            1 u  187  256  377   49.320
> 0.028   1.192
>  ntp0.rrze.uni-e .GPS.            1 u    -  256  377   39.578
> -0.073   0.028
>  ntp1.oma.be     .PPS.            1 u  184  256  377   48.966
> 0.068   0.124
>  time-a.nist.gov .ACTS.           1 u  249  256  377  147.557
> 2.230   2.364
> 
> One may observe the delays were also affected during this interval.
> Also, the time information served to clients was affected, the
> pool.ntp.org monitoring system confirmed the delay -
> http://www.pool.ntp.org/scores/80.96.120.252. It is obvious that a
> server synchronizing only with Internet sources will be in error as
> there is has no way to determine the problem. Can someone explain this
> behavior ?




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