[time-nuts] Basic Stratum 1 question

Hal Murray hmurray at megapathdsl.net
Thu Aug 2 13:40:33 EDT 2007


> Stratum 1, in the ntp world, is a source that's connected to an
> official source of time (the so-called Stratum 0).  The CMOS clock
> isn't connected to NIST, therefore it can't be considered Stratum 1 by
> any stretch of the imagination. 

> Also, Stratum 1, in telco, has certain performance requirements.
...

It's worth pointing out that "stratum 1" in the ntp world doesn't say 
anything about quality.

The ntp stratum levels form a tree.  Within a tree, lower stratum is better.  
Given two trees, the root of one may be much better than the other.  The 
stratum-3 branches on the good tree may be more accurate than the root of the 
not-so-good tree.

ntpd supports a wide collection of clocks.  Some are accurate to a few 
microseconds, some are only good to tens of milliseconds.  The protocol 
includes an estimate of the quality so the client can pick the best clock.



-- 
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