[ntp:questions] SNTP server + ntpd 4.2.4 client

Richard B. Gilbert rgilbert88 at comcast.net
Fri Mar 14 14:44:34 UTC 2008


Noob wrote:
> Hello,
> 
> I've been running ntpd 4.2.4 to synchronize my system clock using remote 
> stratum 2 servers as a reference. (The RTT to these servers is in the 
> 30-50 ms range.) The accuracy is in the 1-2 ms range, based on the 
> reported offset.
> 
> I've been asked to evaluate the following time server, in order to reach 
> a better accuracy than what the current setup provides.
> 
> http://www.heoldesign.com/index.php?id=58
> 

That link takes me to a page advertising THREE products!  Which one did 
you have in mind?

> (AFAIU, this time server implements SNTP, not the full NTP.)
> 
> The idea would be to put this (stratum 1) time server in the same LAN as 
> my box, and add it my ntp.conf. (The RTT on the LAN is on the order of 
> 100 µs.)
> 
> Will it work?
> 

It should work.

> Is it a problem that the time server only implements SNTP?
> 

It should not be a problem.  The largest difference between NTP and SNTP 
is the effort to account for the vagaries of the internet!

> What kind of accuracy may I expect?
> 

These devices should be accurate to within the range of 25 to 100 
nanoseconds.  The limiting factor will be the jitter introduced while 
getting the time into your computer.

A SWAG (Scientific Wild Ass Guess) would be 500 microseconds.  By 
spending a lot of time and effort you might be able to get something 
better than that.  The chief difficulty would be measuring and 
controlling the delays within the computer.








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