[ntp:questions] NTP over redundant peer links, undetected loops

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Wed Feb 11 20:35:07 UTC 2009

Stefan Schimanski wrote:
> Hi!
> We are trying to implement a NTP installation over a redundant
> network, connecting the stratum 2 servers to the stratum 3 clients.
> The precise situation is the following (compare with
> http://1stein.org/download/network.png):
> 3 networks,,,
> ATOM1, ATOM2 - stratum 1 servers in network 3
> GW1, GW2 - stratum 2 servers in all networks, i.e. 3, 4, 5
> CLIENT1...CLIENTn - stratum 3 clients in network 4 and 5

I did quite a bit of work while setting up a big corporate network, with 
dual servers, one of which had a Motorola Oncore UT+, in each of three 
geographically distributed locations.

I had similar plans like you, wanting to setup two or three layers of 
servers, but then I realized that this was totally superfluous!

We had less than 40K server and client machines worldwide, so even if 
every single one of them configured all 6 primary servers, the resulting 
load would be negligible, the timing results would be optimal, and so 
would the redundancy level.

The icing on the cake is that I don't need to consider where a client 
machine is located, I simply tell everyone to use exactly the same 
configuration file, with one exception:

The core/root DNS servers (as well as DHCP servers and some other 
network gear) use the same six servers, but they use the IP addresses 
directly instead of the DNS names.

- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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