[ntp:questions] Re: NTP "maximum error" on local network

Richard B. Gilbert rgilbert88 at comcast.net
Thu May 18 17:55:16 UTC 2006


ajit.warrier at gmail.com wrote:

> ------------------ client 1 -----
> # ntpq -pcrv
>      remote           refid      st t when poll reach   delay   offset
> jitter
> ==============================================================================
> *192.168.2.2     .NIST.           1 u    8   16  377    0.316   -0.004
>  0.049
> assID=0 status=0644 leap_none, sync_ntp, 4 events,
> event_peer/strat_chg,
> version="ntpd 4.2.0a at 1:4.2.0a+stable-8-r Fri Sep  9 16:44:48 UTC 2005
> (1)"?,
> processor="i686", system="Linux/2.6.14-ck1", leap=00, stratum=2,
> precision=-18, rootdelay=0.311, rootdispersion=23.428, peer=30804,
> refid=192.168.2.2,
> reftime=c8170ae1.7219220f  Thu, May 18 2006 11:01:53.445, poll=4,
> clock=0xc8170b1d.39cd0bb6, state=4, offset=-0.008, frequency=212.134,
> noise=0.006, jitter=0.214, stability=0.176
> 
> ----------- client 2 --------------
> 
> # ntpq -pcrv
>      remote           refid      st t when poll reach   delay   offset
> jitter
> ==============================================================================
> *192.168.2.2     .NIST.           1 u    -   16  377    0.327   -0.010
>  0.103
> assID=0 status=06b4 leap_none, sync_ntp, 11 events,
> event_peer/strat_chg,
> version="ntpd 4.2.0a at 1:4.2.0a+stable-8-r Fri Sep  9 16:44:48 UTC 2005
> (1)"?,
> processor="i686", system="Linux/2.6.14-ck1", leap=00, stratum=2,
> precision=-18, rootdelay=0.327, rootdispersion=22.889, peer=7436,
> refid=192.168.2.2,
> reftime=c8170e61.c989df11  Thu, May 18 2006 11:16:49.787, poll=4,
> clock=0xc8170e75.fd7a13c2, state=4, offset=-0.010, frequency=183.551,
> noise=0.005, jitter=0.103, stability=0.165
> 
> -------- server --------------
> 
> # ntpq -pcrv
>      remote           refid      st t when poll reach   delay   offset
> jitter
> ==============================================================================
> *LOCAL(1)        .NIST.           0 l   18   64  377    0.000    0.000
>  0.004
> assID=0 status=0544 leap_none, sync_local_proto, 4 events,
> event_peer/strat_chg,
> version="ntpd 4.2.0a at 1.1190-r Fri Sep 23 21:02:05 EDT 2005 (1)"?,
> processor="i686", system="Linux/2.6.16.14", leap=00, stratum=1,
> precision=-18, rootdelay=0.000, rootdispersion=12.198, peer=11860,
> refid=NIST, reftime=c8170f79.d6b87379  Thu, May 18 2006 11:21:29.838,
> poll=10, clock=0xc8170f8b.90c7b02d, state=4, offset=0.000,
> frequency=0.000, noise=0.000, jitter=0.004, stability=0.000
> 
> -------------------------------------------------------------
> 
> I am trying to build an isolated system, disconnected from the rest of
> the internet, so I set the REFID to "NIST" and stratum to 0. If this is
> a stupid thing to do, please let me know :)
> 

I wouldn't go so far as to call in "stupid" but it is not correct and it 
is not necessary. (But don't ask what I would have said 25 or 30 years 
ago!) If you don't specify the refid, I believe it defaults to ".LCL.", 
".LOCL." or something similar.  That simply says that the reference is 
your local clock.  .NIST. is not correct because it implies that the 
time comes from the National Institute of Standards and Technology when, 
in fact, it does not.

Even if your local clock was originally set to a time taken from NIST, 
there is a 99.99999999% probability that the time has since deviated 
from the correct value.  It is not unusual for a local clock to drift as 
much as four seconds per day.  Some local clocks are much worse than that.




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