[ntp:questions] Selection and Clustering of candidates
Mischanko, Edward T
Edward.Mischanko at arcelormittal.com
Mon Jun 27 12:07:19 UTC 2011
State Remote Refid Stratum Type When Poll
Reach Delay Offset Jitter
# 156.144.102.1 156.144.104.1 4 Unicast server
555 1024 377 23.192 1.465 1.760
+ 156.144.106.1 156.144.104.1 4 Unicast server
751 1024 377 29.431 0.030 1.339
+ 156.144.109.1 156.144.104.1 4 Unicast server
583 1024 377 22.822 -0.005 1.796
# 156.144.110.1 156.144.104.1 4 Unicast server
701 1024 377 22.546 0.855 0.908
+ 156.144.112.1 156.144.104.1 4 Unicast server
699 1024 377 22.950 0.070 1.015
# 156.144.120.1 156.144.104.1 4 Unicast server
646 1024 377 22.829 2.164 1.991
# 156.144.121.1 156.144.104.1 4 Unicast server
547 1024 377 24.809 -0.417 0.742
+ 156.144.122.1 156.144.104.1 4 Unicast server
359 1024 377 22.891 0.153 1.089
+ 156.144.123.1 156.144.104.1 4 Unicast server
388 1024 377 23.672 -0.448 1.056
+ 156.144.124.1 156.144.104.1 4 Unicast server
306 1024 377 37.218 -7.239 7.356
# 156.144.125.1 156.144.104.1 4 Unicast server
91 1024 377 22.781 0.236 1.016
* 156.144.126.1 156.144.104.1 4 Unicast server
453 1024 377 22.692 0.357 0.525
# 156.144.129.1 156.144.104.1 4 Unicast server
595 1024 377 23.330 1.231 1.114
+ 156.144.131.1 156.144.104.1 4 Unicast server
881 1024 377 23.196 0.637 0.763
+ 156.144.134.1 156.144.104.1 4 Unicast server
617 1024 377 23.003 0.057 0.668
Why is 156.144.124.1 selected for clustering? It has the the highest
delay and the highest jitter; it is not needed to synch the clock, as
you can see I have plenty of candidates to choose from.
-----Original Message-----
From: questions-bounces+edward.mischanko=arcelormittal.com at lists.ntp.org
[mailto:questions-bounces+edward.mischanko=arcelormittal.com at lists.ntp.o
rg] On Behalf Of David Woolley
Sent: Sunday, June 26, 2011 4:04 AM
To: questions at lists.ntp.org
Subject: Re: [ntp:questions] Selection and Clustering of candidates
Mischanko, Edward T wrote:
> Some of the servers
> NTP selects have offsets that are higher than the majority;
These might be the ones with the most correct time. A high offset only
indicates a poor time if you are certain that the local time is
absolutely correct.
> Why are they being selected?
Because they have times that are consistent with the times from all the
other selected ones and NTP_MAXCLOCKS in ntpd.h hasn't been reached.
> Why are so many being selected when I really want the best 5 or 6.
How is ntpd to determine that they are the best ones. A high offset may
simply mean the local time is wrong.
>
> # Miscellaneous stuff
> tinker allan 7
> tos minclock 4 minsane 3
It is tos maxclock, but it doesn't seem to be documented in at least
some versions of the HTML.
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