ntp-4.2.8 sychronization in tos orphan mode takes longer compared to ntp-4.2.4

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Environment

SUSE Linux Enterprise Server 11 Service Pack 4 (SLES 11 SP4)
SUSE Linux Enterprise Server 12 Service Pack 2 (SLES 12 SP2)
SUSE Linux Enterprise Server 12 Service Pack 1 (SLES 12 SP1)

Situation

In case the designated time source for a given network is unreachable, the tos orphan option enables NTP clients to sync to a network of specified systems to act as clock source. When updating from ntp-4.2.4 to ntp-4.2.8/ntp-4.2.8p9 the process of synchronization takes longer than before.

Resolution

NTP works as expected.

Cause

In version 4.2.4 ntp considered itself synchronized after a few packages have been exchanged. This was considered a misbehavior and got addressed in 4.2.8.

Additional Information

To check whether ntp operates in tos orphan mode please execute ntpq -p -c rv:

sles11sp41:~ # ntpq -p -c rv
     remote           refid      st t when poll reach   delay   offset jitter
==============================================================================
192.168.66.230 127.0.0.1        8 s 141   64   70    0.789 3598134   0.056
192.168.66.225 127.0.0.1        8 s 133   64   74    0.734 -228.19   0.075
192.168.66.231 127.0.0.1        8 s 195   64   70    0.627 3599820   0.052
associd=0 status=0016 leap_none, sync_unspec, 1 event, restart,
version="ntpd 4.2.8p9@1.3265-o Tue Nov 29 12:37:44 UTC 2016 (1)",
processor="x86_64", system="Linux/3.0.101-91-default", leap=00,
stratum=8, precision=-21, rootdelay=0.000, rootdisp=0.000,
refid=127.0.0.1,
reftime=00000000.00000000 Thu, Feb 7 2036 7:28:16.000,
clock=dc552a48.5017b8c0 Mon, Feb 20 2017 9:41:44.312, peer=0, tc=3,
mintc=3, offset=0.000000, frequency=499.949, sys_jitter=0.000000,
clk_jitter=0.000, clk_wander=0.000

The refid field shows the IP address ntp selected as clock source, after a while the nodes elect a preferred time source, these nodes change the refid to the IP address of this server:

Every 2.0s: ntpq -p -c rv

     remote           refid      st t when poll reach   delay   offset jitter
==============================================================================
192.168.66.230 192.168.66.224   9 s    4   64 377    1.659   -0.465   0.306
192.168.66.225 192.168.66.224   9 s   22   64 373    0.513   -0.064   0.129
192.168.66.231 192.168.66.224   9 s 127   64 374    0.585 -228.37   0.200
associd=0 status=0016 leap_none, sync_unspec, 1 event, restart,
version="ntpd 4.2.8p9@1.3265-o Tue Nov 29 12:37:44 UTC 2016 (1)",
processor="x86_64", system="Linux/3.0.101-91-default", leap=00,
stratum=8, precision=-21, rootdelay=0.000, rootdisp=0.000,
refid=127.0.0.1,
reftime=00000000.00000000 Thu, Feb 7 2036 7:28:16.000,
clock=dc552da1.5405c1b1 Mon, Feb 20 2017 9:56:01.328, peer=0, tc=3,
mintc=3, offset=0.000000, frequency=499.949, sys_jitter=0.000000,
clk_jitter=0.000, clk_wander=0.000

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