[ntp:questions] Can NTP sync within 1ms

William Unruh unruh at invalid.ca
Sat Apr 26 03:22:40 UTC 2014

On 2014-04-26, Joe Gwinn <joegwinn at comcast.net> wrote:
> In article
><8188BA2B01FB534A99C03D79C62CE1D80982FB4C at UUSNWE3A.global.utcmail.com>,
> Montgomery, Peter         BIS <Peter.Montgomery at fs.utc.com> wrote:
>> I am new to NTP. But I have a quick question that I need to answer soon.
>> I would like to know whether NTP can sync between a client and a server
>> within 1ms if the client and server are Linux applications on a simple local
>> network ( less than 10 nodes).
> Not reliably, for a million reasons.  A better rule is 10 milliseconds,
> and even that requires work and care.  

Well, since I have 8 machines that reliably sync from one GPS PPS driven
machine (all using chrony) and they get time reliability of about
10microseconds, your experience seems a bit different than mine. 
And how did you determine that you were only getting 10ms. As I said,
you cannot conclude that by looking at the offsets reported by ntpd.

> The most reliable approach is an IRIG network.

Or put a gps pps receiver onto each  machine. 

> But you need to describe your problem and constraints before people can
> give better answers.


> Joe Gwinn

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