[ntp:questions] Synchronizing using servers in stratum 1 and 2
timo.ruiter at xs4all.nl
Wed Feb 14 18:25:06 UTC 2007
Timo Ruiter schreef:
> Hi all,
> When using pool.ntp.org the DNS randomly select time servers. Since
> stratum-1 servers and stratum-2 servers share the same pool you will get
> a mix of them when using 0.nl.pool.ntp.org, 1.nl.pool.ntp.org, and
> 2.nl.pool.ntp.org for instance.
> When you are assigned *one* stratum-1 server and *two* stratum-2 servers
> your clock will obviously synchronize to the stratum-1 server. But that
> being the case, what is the use of the two stratum-2 servers, assuming
> that the stratum-1 server will not go off-line?
> Could it be so that if the stratum-1 server is not so accurate after all
> it would still be selected over the stratum-2 servers (since no
> reference stratum-1 server is available)?
> Will you not be better served instead when you are assigned *three*
> stratum-2 servers, so the selection process of ntpd will compare all
> three servers equally and choose the best one, switching to another if
> that one looks more stable after a while?
What I really wanted to know is what is better in terms of stability:
*one* stratum-1 server and *two* stratum-2 servers versus *three*
When having only one stratum-1 server available you might be relying on
that server too much; when having three stratum-2 servers (ideally
synchronized to three different stratum-1 servers) time *could* be more
stable since there are three stratum-1 servers involved, albeit through
the stratum-2 servers.
This is a pure theoretical issue as far as I'm concerned, since who can
tell the difference if your servers are 23 milliseconds off...
So replace "stratum-1" by "stratum-N" and "stratum-2" by
"stratum-(N-1)"; the question will remain the same.
More information about the questions