[ntp:questions] long time to report sync per leap indicator, when initial system time is set far into the future

Stephan E. public-se at innominate.com
Tue Dec 12 16:31:09 UTC 2017


On 12/12/2017 10:39 AM, Mike Cook wrote:
> 
> I am pretty sure that this is expected behavior and a configuration error.
> 
> I have tried and failed to reproduce this in either 4.2.8p10 or 4.2.8p9 UNLESS there are NOT ENOUGH sufficiently stable servers available at start up.
> 
> That is to say, that if their reach values does not tend to 377.
> 
> for example if I have only 2 servers configured and only one is stable such as here:
> 
> Tue Dec 12 08:19:11 UTC 2017
>       remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
>   time-c-g.nist.g .NIST.           1 u    5   16  275   95.193  -398059   0.047
>   india.colorado. .NIST.           1 u   14   16  377  130.526  -398062   0.050
> 
> The leap indicator  will remain 11, i.e. unsynchronized
> 
> Tue Dec 12 08:19:03 UTC 2017
> processor="armv7l", system="Linux/3.8.13-bone47", leap=11, stratum=16,
> Tue Dec 12 08:19:08 UTC 2017
> processor="armv7l", system="Linux/3.8.13-bone47", leap=11, stratum=16,
> Tue Dec 12 08:19:13 UTC 2017
> processor="armv7l", system="Linux/3.8.13-bone47", leap=11, stratum=16,
> Tue Dec 12 08:19:18 UTC 2017
> 
> So you should make sure that you select servers that have good connectivity ( closer is better ) and use a minimum of 5.
> 
> So to debug this,  change your date , restart ntpd with just -g and then monitor the server status.  If the servers are showing poor connectivity, change/add .
> 
> Hope this helps


I've added more servers and it does not change the outcome.

To test, from an initially synced time, I
* shut down ntpd
* change the system time by delta
* start ntpd with -g
* record the time it takes until ntpd will reply with LI==0 to requests from clients.
* repeat with a larger delta.

This works well for deltas into the past, but for deltas into the future I get

delta of 15 s took 374 s to sync
delta of 60 s took 380 s to sync
delta of 240 s took 363 s to sync
delta of 960 s took 1285 s to sync
delta of 3840 s took 4843 s to sync
delta of 15360 s took 15569 s to sync

During that waiting period, I get a status of e.g.

     # ./ntpq -c peers
          remote           refid      st t when poll reach   delay   offset  jitter
     ==============================================================================
      ptbtime1.ptb.de .STEP.          16 u    -   64    0    0.000    0.000   0.000
      ptbtime2.ptb.de .STEP.          16 u   20   64    0    0.000    0.000   0.000
      ptbtime3.ptb.de .STEP.          16 u   25   64    0    0.000    0.000   0.000
      ntp2.m-online.n .STEP.          16 u  770   64    0    0.000    0.000   0.000
      1c.ncomputers.o .STEP.          16 u  385   64    0    0.000    0.000   0.000
      ntp1.wtnet.de   .STEP.          16 u  850   64    0    0.000    0.000   0.000
      backup.heikoric .STEP.          16 u 1864   64    0    0.000    0.000   0.000

     # ./ntpq -c rl
     associd=0 status=c018 leap_alarm, sync_unspec, 1 event, no_sys_peer,
     version="ntpd 4.2.8p10 at 1.3728-o Tue Dec 12 11:03:31 UTC 2017 (1)",
     processor="ppc", system="Linux/3.10.104", leap=11,
     stratum=16, precision=-18, rootdelay=0.000, rootdisp=1.620, refid=STEP,
     reftime=00000000.00000000  Thu, Feb  7 2036  6:28:16.000,
     clock=ddda50cf.3c52fb54  Tue, Dec 12 2017 12:57:51.235, peer=0, tc=6,
     mintc=3, offset=0.000000, frequency=0.000, sys_jitter=0.003815,
     clk_jitter=0.004, clk_wander=0.000

(servers #4 ff. are assigned from pool.ntp.org)

But, even then, from "eyeballing" the system clock it appears correct within at least 1 s, and if I now stop and restart ntpd, I almost immediately get

     # ./ntpq -c peers
          remote           refid      st t when poll reach   delay   offset  jitter
     ==============================================================================
      ptbtime1.ptb.de .INIT.          16 u    -   64    0    0.000    0.000   0.000
     +ptbtime2.ptb.de .PTB.            1 u    1   64    1   57.113   -1.902   2.851
     *ptbtime3.ptb.de .PTB.            1 u    2   64    1   57.678   -1.829   7.572
     +ntp2.m-online.n 212.18.1.106     2 u    3   64    1   60.288    1.178   4.073
     +1c.ncomputers.o 222.217.153.8    2 u    1   64    1   73.751   -0.535   4.885
     +ntp1.wtnet.de   10.129.40.211    2 u    1   64    1   57.811    1.985   3.249
     +backup.heikoric 124.216.164.14   2 u    3   64    1   61.142   -0.668   5.216

     # ./ntpq -c rl
     associd=0 status=0614 leap_none, sync_ntp, 1 event, freq_mode,
     version="ntpd 4.2.8p10 at 1.3728-o Tue Dec 12 11:03:31 UTC 2017 (1)",
     processor="ppc", system="Linux/3.10.104", leap=00,
     stratum=2, precision=-18, rootdelay=57.678, rootdisp=192.086,
     refid=192.53.103.103,
     reftime=ddda5126.d1f40191  Tue, Dec 12 2017 12:59:18.820,
     clock=ddda512b.edb0de7d  Tue, Dec 12 2017 12:59:23.928, peer=46425, tc=6,
     mintc=3, offset=0.209764, frequency=0.000, sys_jitter=2.308874,
     clk_jitter=0.720, clk_wander=0.000



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