[ntp:questions] Re: simple time server

Richard B. Gilbert rgilbert88 at comcast.net
Thu Aug 3 01:32:20 UTC 2006

Bryan Henderson wrote:

>>if you were expecting to
>>have to start a program everytime, you weren't particularly interested in
>>high accuracy.
> Sure I was.  The program takes however long it needs to start up and
> then tells the client "The time right now is precisely ..."  The
> client gets the message and knows that the time at that moment is that
> plus transmission delay.  Ideally, it uses NTP so as to eliminate the
> transmission delay as well.

It takes a couple of hours for the program to figure out "what the time 
is precisely".  It can then tell some other system that the time, just a 
moment ago, was "precisely. . . ."   That second system's notion of what 
time it is will be slightly less accurate than that of the first system.

Once that first system has synchronized its clock, ntpd can maintain 
synchronization.  If you shut down ntpd, you can expect to wait a while 
before it, again, figures out "precisely what time it is".  Most people 
leave their NTP servers running 24x7 when possible.

And NTP does not "eliminate the transmission delay".  It assumes that 
the round trip delay is symmetrical and only if the delay is truly 
symmetrical does it account for the delay exactly.

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