From: Brian Dennis (brian@xxxxxx)
Date: Wed Aug 28 2002 - 00:43:09 GMT-3
A NTP client queries for the reference time from a NTP server. A device
is a NTP client if it is only receiving reference time from other
devices (NTP servers).
A NTP server acts as a time reference for NTP clients. A device is a NTP
server if it is only providing a time reference to other devices (NTP
clients).
A NTP peer compares its time to other NTP peers until all the peers
finally agree upon the correct time to synchronize too. A device is a
NTP peer if it is receiving from "and" providing a time reference with
other devices (NTP peers).
Brian Dennis, CCIE #2210 (R&S/ISP Dial)
-----Original Message-----
From: Volkov, Dmitry (Toronto - BCE) [mailto:dmitry_volkov@ca.ml.com]
Sent: Tuesday, August 27, 2002 8:13 PM
To: 'Nick Shah'; 'Dan.Thorson@seagate.com'; 'Brian Dennis'
Cc: 'ccielab@groupstudy.com'
Subject: RE: NTP server/peer
Nick, Brian, Dan,
Still - not clear.
> -----Original Message-----
> From: Nick Shah [mailto:nshah@connect.com.au]
> Sent: Tuesday, August 27, 2002 10:02 PM
>
> How/Where can you use it ? Well, in a distribution layer you
> could have
> 'peers' who can synchronise with each other, when a server is
> unreachable.
3 scenarios:
1) Two boxes without lower stratum clock source:
R1---------R2 on R1: ntp peer (ip add of r2) on R2: ntp peer (ip add of
r1)
They don't sync each other - their stratum 16 (and even don't try - i
checked via debug)
The same situation using "ntp server" pointing to each other. If no
clock
source (stratum lower than 16) - No sync.
2)
If I have one box synchronized with lower stratum, I can setup other box
to
get time from first box using "ntp peer" or "ntp server" - I don't see
difference ...
3) If I have two lower stratum clock sources with IP a.a.a.a and IP
b.b.b.b
I configure two boxes:
3.I) with "ntp server a.a.a.a prefer" and "ntp server b.b.b.b"
3.II) with "ntp server b.b.b.b prefer" and "ntp server a.a.a.a"
Why Dan did use "ntp peer" in this case ?
> Remember a Server would be at a lower stratum number hence
> more preferable,
> in absence of which, the Peers can choose to synchronise with
> either/each
> other.
> And last but not least, the most important rule, no client/peer will
> synchronise with the Server/Peer if that server/peer is in turn not
> not synchronised with itself.
What does it mean - "not synchronised with itself" ? How it can be sych
with
itself ?
I guess using "ntp master" only ?
Thanks,
Dmitry
> rgds
> Nick
>
> ----- Original Message -----
> From: "Volkov, Dmitry (Toronto - BCE)" <dmitry_volkov@ca.ml.com>
> To: <ccielab@groupstudy.com>
> Sent: Wednesday, August 28, 2002 7:31 AM
> Subject: NTP server/peer
>
>
> > Hello,
> >
> > Can somebody explain the difference between "ntp server"
> and "ntp peer"
> > commands ?
> >
> > I always used to use "ntp server".
> >
> > I read this:
> >
> http://www.cisco.com/univercd/cc/td/doc/product/software/ios12
1/121cgcr/fun_
> c/fcprt3/fcd303.htm#xtocid2708216
> and Doyle and Solie... and still don't understand when is suitable to
use
> "ntp peer".
>
>
> Thanks,
>
> Dmitry
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