Re: [chrony-users] Sporadic NTP dropouts (bad maximum delay ratio and maximum delay dev ratio)

[Ulrich Schwesinger <ulrich.schwesinger@xxxxxxxxxxxx>]

Thanks for the helpful feedback so far. I contacted the server admin, and he says there should be nothing that makes the server jump...

I am wondering about a couple of things:

• Is there any specific test among these all, or a combination of those which will make the status go to unsynched?
  
• Why is there for example an 8 seconds gap in the log entries? Usually they are < 1 second. It also looks to me that score and root dispersion (sorry, not sure what that exactly is) are kind of "reset" when that happens.
  
• Why does the stratum test fail? Can you explain what happens?

I have attached another failure case with information from all 3 logs. I really appreciate you guys helping, thanks!!

========================================================================================================================
   Date (UTC) Time     IP Address   L St 1234 abc 5678 LP RP Score Offset     Peer del. Peer disp. Root del.  Root disp.
========================================================================================================================
2015-05-26 10:50:33 192.168.0.30    N 13 1111 111 1111  5  5 0.00  1.800e-05  6.681e-04  8.968e-02  0.000e+00  7.948e+00
2015-05-26 10:50:35 192.168.0.30    N 13 1111 111 1111  5  5 0.00  5.542e-03  5.040e-04  6.726e-02  0.000e+00  7.948e+00
2015-05-26 10:50:37 192.168.0.30    N 13 1111 111 1111  5  5 0.00  1.350e-02  6.620e-04  3.784e-02  0.000e+00  7.947e+00
2015-05-26 10:50:39 192.168.0.30    N 13 1111 111 1111  5  5 0.00  3.107e-03  6.741e-04  1.877e-02  0.000e+00  7.948e+00
2015-05-26 10:51:12 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -2.444e-03  6.790e-04  3.731e-06  0.000e+00  7.948e+00
2015-05-26 10:51:44 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -3.990e-03  7.220e-04  1.744e-06  0.000e+00  3.948e+00
2015-05-26 10:52:17 192.168.0.30    N 13 1111 111 1111  5  5 0.03 -4.055e-03  6.850e-04  1.116e-06  0.000e+00  3.948e+00
2015-05-26 10:52:49 192.168.0.30    N 13 1111 111 1111  5  5 0.08 -2.306e-03  6.820e-04  1.141e-06  0.000e+00  1.948e+00
2015-05-26 10:53:22 192.168.0.30    N 13 1111 111 1111  5  5 0.17  1.900e-05  6.740e-04  1.060e-06  0.000e+00  1.949e+00
2015-05-26 10:53:54 192.168.0.30    N 13 1111 111 1111  5  5 0.28 -3.000e-05  6.620e-04  1.122e-06  0.000e+00  9.482e-01
2015-05-26 10:54:26 192.168.0.30    N 13 1111 111 1111  5  5 0.42  0.000e+00  6.820e-04  1.144e-06  0.000e+00  9.487e-01
2015-05-26 10:54:58 192.168.0.30    N 13 1111 111 1111  5  5 0.58 -2.400e-05  6.940e-04  1.046e-06  0.000e+00  4.483e-01
2015-05-26 10:55:31 192.168.0.30    N 13 1111 111 1111  5  5 0.78 -1.200e-05  7.160e-04  1.100e-06  0.000e+00  4.488e-01
2015-05-26 10:56:03 192.168.0.30    N 13 1111 111 1111  5  5 1.00 -4.000e-05  6.740e-04  1.069e-06  0.000e+00  1.984e-01
========================================================================================================================
   Date (UTC) Time     IP Address   L St 1234 abc 5678 LP RP Score Offset     Peer del. Peer disp. Root del.  Root disp.
========================================================================================================================
2015-05-26 11:04:25 192.168.0.30    N 13 1111 111 1111  5  5 0.00 -2.820e-04  6.490e-04  2.336e-06  0.000e+00  7.948e+00
2015-05-26 11:04:27 192.168.0.30    ? 16 1111 111 1001  5  5 0.00 -6.820e-04  6.341e-04  2.336e-06  0.000e+00  0.000e+00


==============================================================================================================
   Date (UTC) Time     IP Address    Std dev'n Est offset  Offset sd  Diff freq   Est skew  Stress  Ns  Bs  Nr
==============================================================================================================
2015-05-26 10:50:37 192.168.0.30     7.903e-04 -1.340e-02  5.192e-04 -3.315e-03  2.150e-01 1.7e+00   3   0   3
2015-05-26 10:50:39 192.168.0.30     1.205e-03 -3.355e-03  6.819e-04 -2.391e-03  1.222e-02 4.3e-03   4   0   3
2015-05-26 10:51:12 192.168.0.30     1.044e-04  2.444e-03  4.670e-05  8.745e-06  8.600e-04 2.0e-01   5   0   3
2015-05-26 10:51:44 192.168.0.30     1.013e-04  3.988e-03  6.019e-05  1.231e-04  2.202e-05 1.3e-01   6   0   3
2015-05-26 10:52:17 192.168.0.30     8.010e-05  4.048e-03  4.742e-05  1.236e-04  7.696e-06 3.0e-02   7   0   3
2015-05-26 10:52:49 192.168.0.30     6.815e-05  2.296e-03  3.978e-05  7.004e-05  3.901e-06 4.0e-02   8   0   3
2015-05-26 10:53:22 192.168.0.30     5.993e-05 -1.048e-05  3.397e-05 -5.451e-08  2.333e-06 3.4e-02   9   0   4
2015-05-26 10:53:54 192.168.0.30     5.444e-05  1.598e-05  2.981e-05  1.334e-07  1.557e-06 5.8e-02  10   0   5
2015-05-26 10:54:26 192.168.0.30     4.982e-05  2.656e-07  2.672e-05  1.351e-08  1.111e-06 1.0e-03  11   0   6
2015-05-26 10:54:58 192.168.0.30     4.679e-05  9.727e-06  2.459e-05  6.208e-08  8.430e-07 5.4e-02  12   0   7
2015-05-26 10:55:31 192.168.0.30     4.411e-05  4.470e-06  2.280e-05  3.192e-08  6.599e-07 2.7e-02  13   0   7
2015-05-26 10:56:03 192.168.0.30     4.294e-05  1.455e-05  2.140e-05  7.539e-08  5.373e-07 1.1e-01  14   0   9
==============================================================================================================
   Date (UTC) Time     IP Address    Std dev'n Est offset  Offset sd  Diff freq   Est skew  Stress  Ns  Bs  Nr
==============================================================================================================
2015-05-26 11:04:38 192.168.0.30     5.068e-06  2.591e-03  6.470e-06  1.735e-04  3.579e-04 8.7e-02   3   0   3
2015-05-26 11:04:40 192.168.0.30     5.523e-06  3.857e-04  5.336e-06  1.739e-04  1.352e-05 1.0e-03   4   0   3

==================================================================================================
   Date (UTC) Time     IP Address   St   Freq ppm   Skew ppm     Offset L Co  Offset sd Rem. corr.
==================================================================================================
2015-05-26 10:50:33 0.0.0.0          0    -76.325      0.364  0.000e+00 ?  0  0.000e+00  0.000e+00
2015-05-26 10:50:37 192.168.0.30    14    -76.325      0.364 -1.341e-02 N  1  5.192e-04 -1.135e-01
2015-05-26 10:50:39 192.168.0.30    14    -76.325      0.364 -3.356e-03 N  1  6.819e-04 -5.630e-02
2015-05-26 10:51:12 192.168.0.30    14    -76.325      0.364  2.444e-03 N  1  4.670e-05 -4.000e-06
2015-05-26 10:51:44 192.168.0.30    14    -76.224      3.906  3.988e-03 N  1  6.019e-05  0.000e+00
2015-05-26 10:52:17 192.168.0.30    14    -22.335     66.861  4.048e-03 N  1  4.742e-05  0.000e+00
2015-05-26 10:52:49 192.168.0.30    14     47.622      6.329  2.296e-03 N  1  3.978e-05  0.000e+00
2015-05-26 10:53:22 192.168.0.30    14     47.570      2.518 -1.048e-05 N  1  3.397e-05  0.000e+00
2015-05-26 10:53:54 192.168.0.30    14     47.688      1.708  1.598e-05 N  1  2.981e-05  4.000e-06
2015-05-26 10:54:26 192.168.0.30    14     47.700      1.189  2.656e-07 N  1  2.672e-05 -4.000e-06
2015-05-26 10:54:58 192.168.0.30    14     47.753      0.914  9.727e-06 N  1  2.459e-05 -3.000e-06
2015-05-26 10:55:31 192.168.0.30    14     47.780      0.709  4.470e-06 N  1  2.280e-05 -1.000e-06
2015-05-26 10:56:03 192.168.0.30    14     47.843      0.593  1.455e-05 N  1  2.140e-05 -2.000e-06
==================================================================================================
   Date (UTC) Time     IP Address   St   Freq ppm   Skew ppm     Offset L Co  Offset sd Rem. corr.
==================================================================================================
2015-05-26 11:04:25 0.0.0.0          0    -76.325      0.364  0.000e+00 ?  0  0.000e+00  0.000e+00

Am 28.05.2015 um 22:14 schrieb Bill Unruh:

On Thu, 28 May 2015, Ulrich Schwesinger wrote:


Tests 1234 abc 5678 are defined in the ntp specifications.

From RFC 1305

TEst 1 and 2 test to make sure that the timestamps make sense (eg are not the
wsame as an old packet and pairs with the last one sent to that peer) test3 is
that the originate and receive timestamps are non-zero, Test 4 is taht the
delay (round trip time) be reasonable, abc are subsets of that, 5 is
authentication, test 6 irequires peer clock by synchronized and that the
itnerval since the peer clock was last updated is positive and less than
NTP.MAXAGE, test 7 that the host has no lower stratum than the server, and 8
that the header contains reasonable values for rootdelay and rootdispersion.

Ie, if any of the tests are out the server's time is too suspect to use. Your
server is problematic.

I marked some lines that look suspicious to me. In in the first line, some test seems to fail [110]. In the 2nd line, suddenly
the offset jumps up to -1.9 seconds.
For the 3rd line, from the documentation I found this:

Leap status: ? means the remote computer is not currently synchronised.
5678: Tests for maximum delay, maximum delay ratio and maximum delay dev ratio, against defined parameters, and a test for
synchronisation loop (1=pass, 0=fail) [1111]

So that would mean that delay ratio and delay dev ratio is bad...not sure what that really means though.

It means that the round trip time is out of spec. And it looks like your
source, whatever that is, went nuts and jumped by 2 sec suddenly. that is why
you should be using at least 3 sources. If one goes mad, the others can
outvote it. If you only use 1, then its time is by definition right, even if
it is out by 40 years.

I find this very hard to debug, is there any other thing I could do to find out what's exactly going wrong?

Talk to the person who is sysadmin on the server and find out what happened. Use more than one server.

Thanks for your answers in advance,

Ulrich