[ntp:questions] Number of Stratum 1 & Stratum 2 Peers

Martin Burnicki martin.burnicki at meinberg.de
Mon Dec 8 08:41:33 UTC 2014


Phil W Lee wrote:
> Martin Burnicki <martin.burnicki at meinberg.de> considered Fri, 05 Dec
> 2014 14:15:31 +0100 the perfect time to write:
>> You may run into problems if your WAN connection has asymmetric delays,
>> and thus to 2 servers on the WAN *seem* to have the same offset which
>> differs from the offset provided by the 2 servers on the local network.
>>
>> Martin
>
> In a multi-site business, I would set up two on each site, and have
> each site using the two local ones and two from different remote
> sites, which should guard against asymmetry on either one of the WAN
> links to other sites.

If the connection from your local site to the internet has the asymmetry 
then *each* NTP server at a remote site has the same additional 
systematic offset, so if you use more than 2 they can overvote your 
local NTP servers.

One of our customers had such a case, and I've explained this in more 
detail in another thread recently.

Martin



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