[ntp:questions] A question

David Woolley david at ex.djwhome.demon.co.uk.invalid
Fri May 2 21:50:51 UTC 2008


Bruno Cocciaro wrote:

> Are you meaning that the easist way is to keep my pc clock synchronized (for
> example using Dimension 4) and send the enquiry to my pc clock ?

Note, if you are using Windows, the time resolution is rather limited 
(about 16ms, but maybe better with multimedia timers on).  If you are 
close enough to a good time server that you can directly read the time 
more accurately than the resolution of the Windows clock, it may be 
better to access it directly, but given the questions you ask, you will 
need the services of a programmer.  Tell them to read the TSC before 
making the request and subtract off half the change in its value, 
converted to appropriate units, between the request and the response.

Don't use Dimension 4, use the reference implementation of ntpd.  As far 
as I know, Dimension 4 isn't open source, so it will be difficult to 
work out how it works, but it is not going to be better than the 
reference implementation, and is probably worse.

If you need better than 16ms, you might be able to query a copy of the 
reference implementation of ntpd, running on the same machine, as that 
keeps time to better than 16ms, but you would probably be better running 
a Unix/Free BSD/Linux machine on the same LAN segment.
> 




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