From: Volkov, Dmitry (Toronto - BCE) (dmitry_volkov@xxxxxxxxx)
Date: Wed Aug 28 2002 - 01:22:14 GMT-3
> -----Original Message-----
> From: Brian Dennis [mailto:brian@5g.net]
> Sent: Tuesday, August 27, 2002 11:43 PM
>
> 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).
r0: ntp master; ntp source lo0; int lo0 ip address a.a.a.a
r1: ntp server a.a.a.a (r1 - is ntp client of a.a.a.a), - r1 queries r0 for
the reference time ==> r0 is ntp server for r1
r2: ntp server r1.r1.r1.r1 - r2 -is client of r1, hence r1 is server for r2
- Right ?
server doesn't know who is client - it is promiscuous.
client, configured with server ip, asks server about time.
So, One way Client QUERY---> Server, Client<---- RESPONSE Server
Everything above is clear.
Now R1 configured as client of server r0.
and R1 configured with "ntp peer r2.r2.r2.r2"
R2 doesn't have ANY explicit ntp configuration.
R1 provides time to R2 without any queries from r2. R2 syncronized with r0.
That what did You mean ?
I just setup it with "debug ntp pack" on r2 - it works as described.
Thanks,
Dmitry
>
> 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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