[time-nuts] Discipline an oscillator with NTP?

[Bob Camp]

Hi

WWV "as transmitted" is massively more accurate than it is as received. There are a lot of NTP servers out there with offsets in the ms to fraction of a ms range. Even if your path was perfect, those issues would keep you from getting to the us level. You could indeed build up some custom servers and take care of the issue. At least  as I understood the original question, random servers on the net were the time source. I assume you would pick them for short path to your location, and then reject any that did really stupid stuff. 

Bob

On Jul 23, 2011, at 2:02 PM, Chris Albertson wrote:

> On Sat, Jul 23, 2011 at 10:40 AM, Bob Camp <lists at rtty.us> wrote:
> 
>> There's also the basic "do I trust the server" issue. You can indeed trust WWV as transmitted.
> 
> NTP's clock selection algorithm is pretty good.  If you choose a
> diverse set of servers then NTP will only use the subset of them that
> are self consistent.  "Pool" servers are assigned randomly so even if
> there were many bad servers in the world the chance of randomly
> picking five that were are "bad" in the exact same way is about zero.
> Typically when a server has a problem it does not match another
> randomly selected ntp server.
> 
> So I think you can trust the consensus time from a set of five
> randomly selected pool servers.  It would be far easier to spoof WWV,
> just set up a transmitter.
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
> 
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