[ntp:questions] Network problems affecting NTP

Eugen COCA ecoca at eed.usv.ro
Fri Jul 1 20:14:25 UTC 2011


Due to a network problem on our provider, the packets were routed on a
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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