[ntp:questions] Re: Peer configuration question?

Nicholas Garfield Nicholas.Garfield at cern.ch
Fri Jan 30 08:04:02 UTC 2004


Thanks for such a concise reply.  You have summed up nicely what I wanted
confirming about peers.....
so how does the "prefer" statement effect this scenario?  Suppose you have a
preferred "server" and a non-preferred "peer".
Will the server always win?  Suppose neither are "preferred", will the
"peer" always take precedence over a server?
I realize this is probably just pedantic, but I really want to understand
the dynamics of such a system.



"Richard B. Gilbert" <rgilbert88 at comcast.net> wrote in message
news:OcednU09jIRVAITdRVn_iw at comcast.com...
> The difference between peers and servers is very simple!
> Peers have a symmetric association; either one can supply time to the
> other.  If two peers have different opinions as to what time it is, they
> will try to determine who has the more accurate time and both will use
> that time.
> Servers are asymmetric; a server can supply time to you but will not
> accept time from you.
> For maximum reliability, you would have your two stratum 1 servers
> configured as peers.  If everything is working properly, these two
> servers should track each other and the "correct" time within a few
> microseconds.  If either GPS receiver fails, the server it is connected
> to will obtain the correct time from its peer and continue to serve its
> clients.  If you have a network neighbor who also operates stratum 1
> servers you might wish to peer with his servers as well.  A setup like
> that gives you both a defense in depth against failures of reference
> clocks, or servers.
> Configure your stratum 2 servers to peer with each other and to be
> served by both stratum 1 servers.  All clients should be served by the
> stratum 2 servers.
> Your single point of failure would be the GPS satellite system itself.
> Highly unlikely but the DOD could just pull the plug on all those
> satellites. . . .
> Nicholas Garfield wrote:
> >Hi All,
> >
> >I have two stratum 1 servers which are each connected to Trimble Accutime
> >GPS receivers.  Then two more servers use these sources as stratum 2
> >servers.
> >I have been reading the NTP FAQ Section 6.2. Advanced Configuration,
> >I am unsure of the configuration.
> >
> >(1) For the stratum 1 servers, should there be a peering relationship
> >between them?
> >
> >ie on server 1 config is
> >
> >server prefer minpoll 4 maxpoll 4 #ACCUTIME
> >peer version 4 minpoll 4 maxpoll 4 #SERVER 2
> >
> >On server 2 config is
> >
> >server prefer minpoll 4 maxpoll 4 #ACCUTIME
> >peer version 4 minpoll 4 maxpoll 4 #SERVER 1
> >
> >Also, would someone be kind enough to clarfiy whether or not the "prefer"
> >keyword is necessary here.  I figure (probably incorrectly) that I would
> >prefer the time to come from the accutime, but how would this work with
> >idea of selecting the "best" clock.
> >
> >(2) Similarly the config for the stratum 2 servers uses peering.
> >
> >I am not 100% clear what the difference between a "server" declaration
and a
> >"peer" declaration is.  When a server and a peer is specified how does
> >choose which is preferred?
> >
> >Thankyou in advance to anyone who can explain clearly when/where the peer
> >and prefer statements should/should not be used.
> >
> >Regards
> >
> >Nick
> >
> >
> >
> >

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