[ntp:questions] Beginner's questions to NTP configuration option "peer"

Nottorf, Stefan Stefan.Nottorf at plath.de
Tue Sep 2 13:55:45 UTC 2008


Hello,
I am quite new to questions regarding time synchronisation and hope this
is the right place to post my questions. I am trying to configure time
synchronisation via NTP in a small to medium size network. Reading
through several web pages and parts of the book of Mr. Mills I still
have some questions, which I will post after briefly describing a part
of the network.
The network has a Meinberg GPS 167 clock, which serves as source for all
time synchronisation. Usage of public time servers is not possible,
because the network is isolated.
Of each blade enclosure, one blade uses the Meinberg clock as time
server and is the timeserver for other blades in the enclosure it is
located in. The stratum 2 blades then use each other as peers. In case
of a failing clock, these servers pretend to be stratum 5 (via fudge).
My questions are:
1) in the described network setup: if the stratum 2 host of an enclosure
1 fails to synchronize with it's stratum 1 source...
before:

|-------------|
| Lantime V4  |
| Stratum 1   |
|-------------|
      |
      |
      V
|-------------|              |-------------|
| Enclosure 1 |<--peer------>| Enclosure 2 |
| Blade 1     |              | Blade 1     |
| Stratum 2   |              | Stratum 2   |
|-------------|              |-------------|
      |
      |
      V
|-------------|
| Enclosure 1 |
| Blade 2     |
| Stratum 3   |
|-------------|

---------------------------
after:

|-------------|
| Lantime V4  |
| Stratum 1   |
|-------------|
      |
      X
      
|-------------|              |-------------|
| Enclosure 1 |<--peer------>| Enclosure 2 |
| Blade 1     |              | Blade 1     |
| Stratum ?   |              | Stratum 2   |
|-------------|              |-------------|
      |          ___________/
      |         /
      V        /
|-------------|
| Enclosure 1 |
| Blade 2     |
| Stratum 3   |
|-------------|

In the documentation it is written that "Should one of the peers lose
all reference sources or simply cease operation, the other peers will
automatically reconfigure so that time and related values can flow from
the surviving peers to all hosts in the subnet". Does the above
ASCII-art describe this behaviour correctly?
2) If a stratum 2 host has peer connections to other stratum 2 hosts AND
it's network connection to the stratum 1 server(s) fail... Does the host
in question
   a) drop to stratum 3 (because it's next time source is the stratum 2
peer) like it would if both peer sides used each other as time server
via the "server" keyword? 
   b) drop to it`s fudged stratum level (stratum 5 in this case)?

Regards,
Stefan




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