[ntp:questions] Setting Up NTP Subnet

Danny Mayer mayer at ntp.isc.org
Tue Mar 7 18:30:00 UTC 2006

Bill Myers wrote:
>  I have questions regarding best practices on architecture of NTP subnets.
> I've thoroughly read "Notes on Setting up a NTP subnet" from the NTP sites.
> Is there a need for multiple external time source TECHNOLOGIES.  That is, is
> it sufficient to use multiple (8) GPS receivers with ACTS dial backup
> and Rubidium clocks?   This is a sizeable investment for the infrastructure,
> but is it the right way?  Is it necessary or desirable to have other sources
> such as radio and/or Internet?

I don't think that there is any specific reason to require this. I don't
think you gain or lose anything by having different technology sources
or identical technology sources. Even on identical ones from the same
manufacturer you will get slightly different results just due to the
manufacturing process. Quality controls on the manufacturing have
tolerances for what will be allowed but that's a range and your gizmo is
going to be anywhere in that range.

> In case you have not picked up on it, I'm talking about an appliance here.
> I find it odd that one cannot NTP peer these appliances.  This suggests to
> me that we should create a stratum 2 tier peer layer a stratum 3 tier that
> peers and serves time to the endpoints.
I don't think that's necessary. The lower the stratum the bigger the
error budget, so depending on how accurate you want your time to be you
need to limit how low you are able to go.

> More dysfunction?  The plan is for the stratum 2 tier, which is also the
> time distribution tier, to be the cache DNS for some high-volume data center
> environments.

Which should be fine. What is the time going to be used for in relation
to the cache DNS?


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