[ntp:questions] Re: Small fixed offset

John Pettitt jpp at cloudview.com
Fri Oct 28 15:34:01 UTC 2005


ariel.burbaickij at gmail.com wrote:
> Neither, nor.
> 
> We have network in central part of USA. There some traffic
> is flowing. Monitoring equipment is located in Central Europe (there
> are plenty of reasons for placing it there). Signals from
> USA are backhauled via optical fibre cable to this
> monitoring equipment. Monitoring equpment represents
> NTP client which gets the time from NTP server also located
> in Central Europe. All signals from network in States are timestamped
> at their arrival at the interface of monitoring equipement. Now, as the
> timestamp should show the time as the signals were indeed on wire
> in States and not the time they were on wire in States + network
> latency time   the clock on the monitoring equipment must be
> slightly behind (150 ms) from the real time. So how we intend
> to do this is to feed the monitoring equipment with the time
> from NTP server with GPS unit locally attached with the the fudge value
> of -150 ms.  Is it workable approach?
> 

It would make more sense to make the offset a variable in the code
that actually does the timestamping.  I say this becasue in years to
come some poor sysadmin who doesn't know the history is going to say
"the time on this box is off 150ms, I'll fix that" and you'll be
screwed.   It's almost always better to put application specific hacks
in the application not the system.




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