[ntp:questions] Re: What can be uses as an SNTP server

Brian T. Brunner brian.t.brunner at gai-tronics.com
Tue Jun 14 14:32:16 UTC 2005


In "The Real World", isolation is an Eternal Transient.

It might also be an unknown.

I've commented here about my manufacture of an embedded alarm/page 
system with a LAN between the systems in the site.
I have NO CLUE what the customer does with my product, I get calls when 
things break. 
Ergo my customer might see nothing wrong is using my cat5 cable to allow 
two PCs in different parts of the plant/ship/rig to talk together.

REGARDLESS of this being violation of Sellers Implementation Plan, 
I'd like for it NOT to amount to a minefield with "time-bombs" in the form 
of my systems lying that I'm stratum 1.

Stratum 10 ("I'm drunk and lost, follow at your own risk... know any good 
drinking songs?") appeals to my grasp of this matter much better than 
stratum 1 ("This Sayeth the Time Lord").

Another concern I don't see addressed is INTERMITTENT internet 
connection. If the off-shore rig has a leased line that may be used (4:AM 
daily) to fetch e-mail, I could grab time from a REAL stratum 1 at that time.  
I'd then coast on that reading until the next day.  ntp.conf would need a 
polling TIME rather than a polling INTERVAL.  Local clock discipline might 
take a few weeks in this scenario, but that is preferable to coasting forever.

(I am attempting to persuade folks to make Real Time a requirement that
the customer supplies, or else we supply).

Brian Brunner
brian.t.brunner at gai-tronics.com
(610)796-5838

>>> "Richard B. Gilbert" <rgilbert88 at comcast.net> 06/13/05 09:01AM >>>

I thought that the concern with unsynchronized local clocks on an 
isolated net operating at a low stratum was that the isolation might not 
be preserved!

A high stratum should be plenty of warning if such a system did get 
connected to the internet.

Some subnets are isolated because there is no internet connection 
available, some because a connection to the internet is forbidden for 
security reasons and perhaps there might be other reasons.  I think that 
all of the above are subject to change with varying probabilities of 
such a change.

I think that any new RFC for NTP should specify a safe way (for the rest 
of the world) to set up such an isolated net.  It should, of course, 
include appropriate warnings about the limitations of such a setup and 
the suggestion the NTP might be the wrong tool for the job.  (All right, 
it IS the wrong tool but people want  their clocks synchronized and 
don't really care what time it is and NTP is there. . . .    There's no 
point in fighting a battle already lost.)

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