Peering recommendation

Hi.

I've been searching the net for recommendation about peering
and how to
avoid synchronisation loops, but I haven't found anything
that answers
my questions.

Almost every time I see a picture about NTP, peering is
drawn like my
"case1" below, but I never seen an explenation
saying, it must look like
this or you have to do it in a certain way.

Can peering be done as described in my case2 and case3 or
should anyone
of them be avoided?

Case1
|-------|       |-------|       |-------|       |-------|
|server1| <---> |server2| <---> |server3|
<---> |server4|
|-------|       |-------|       |-------|       |-------|
    


Case2
|-------|       |-------| 
|server1| <---> |server2| 
|-------|       |-------| 
    ^               ^
    |               |
    |               |
    v               v
|-------|       |-------|
|server3| <---> |server4|
|-------|       |-------|


Case3
|-------|       |-------| 
|server1| <---> |server2| 
|-------|<     >|-------| 
    ^        /     ^
    |       /      |
    |       X       |
    |      /       |
    v     /        v
|-------|<     >|-------|
|server3| <---> |server4|
|-------|       |-------|

Best regards
Uffe
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ulf.norbergbanverket.se wrote:
> Hi.
> 
> I've been searching the net for recommendation about
peering and how to
> avoid synchronisation loops, but I haven't found
anything that answers
> my questions.
> 
> Almost every time I see a picture about NTP, peering is
drawn like my
> "case1" below, but I never seen an
explenation saying, it must look like
> this or you have to do it in a certain way.
> 
> Can peering be done as described in my case2 and case3
or should anyone
> of them be avoided?
> 
> Case1
> |-------|       |-------|       |-------|      
|-------|
> |server1| <---> |server2| <---> |server3|
<---> |server4|
> |-------|       |-------|       |-------|      
|-------|
>     
> 
> 
> Case2
> |-------|       |-------| 
> |server1| <---> |server2| 
> |-------|       |-------| 
>     ^               ^
>     |               |
>     |               |
>     v               v
> |-------|       |-------|
> |server3| <---> |server4|
> |-------|       |-------|
> 
> 
> Case3
> |-------|       |-------| 
> |server1| <---> |server2| 
> |-------|<     >|-------| 
>     ^        /     ^
>     |       /      |
>     |       X       |
>     |      /       |
>     v     /        v
> |-------|<     >|-------|
> |server3| <---> |server4|
> |-------|       |-------|
> 
> Best regards
> Uffe
> _______________________________________________
> questions mailing list
> questionslists.ntp.isc.org
> 
https://lists.ntp.isc.org/mailman/listinfo/questions
> 

Forget the diagrams and concentrate on the configuration
files!

For example, on server1:

peer server2
peer server3
peer server4

On server2
peer server1
peer server3
peer server4

etc.  Draw your own picture if you must, I won't even
attempt it!

FWIW and IMHO, to whatever exent my opinions might be
"humble" , each
peered server needs at least one unique source of time. 
Without that 
unique source of time the peers can all be wrong in the same
way and 
have no means of detecting the problem.

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