[ntp:questions] Clock selection in Orphan Mode

unruh unruh at invalid.ca
Fri Jul 26 23:13:44 UTC 2013


On 2013-07-26, E-Mail Sent to this address will be added to the BlackLists <Null at BlackList.Anitech-Systems.invalid> wrote:
> Mathieu Deltorre wrote:
>> I'm working to configure NTP in an isolated network
>>  (no UTC source time available).
>> I have 3 PCs configured in orphan mode and broadcast mode :
>>   broadcast 220.0.0.255
>>   broadcastclient
>>   tos orphan 1
>
> I'd set that higher like maybe 10 {then maybe that's just me}.
>
>
>>   tos orphanwait 0
>>   tinker panic 0
>> adress IP PC1 : 220.0.0.1
>> adress IP PC2 : 220.0.0.2
>> adress IP PC3 : 220.0.0.3
>>
>> All is fine: When started ntp daemon on each PCs,
>>   after a while, PC2 and PC3 are synchronized to PC1 (LOOP refid).
>>  I've seen in html NTP documentation and in NTP code,
>>   that clock selection is based on the lowest adress IP
>>  (adress IP of PC1 in my case).
>>
>> First question : Is my undestanding is correct ?
>
> Really, references?
>  I doubt it, unless you mean as a final tie breaker,
>   everything else being equal (which is fairly unlikely).

No, I beleive he means which IP is used as the reported time source.
AFAIK ntpd does it voting as to which are good and which are
falsetickers. It then uses and average of the good clocks, but assigns
that group time to one of the clocks in the group of good clocks. That
it is the lowest IP would not surprize me, but clearly your next
sentence is a good source (assuming that the OP is able to disentagle
the code to figure out what it is doing).

>
>  The way to tell, is to just read the source code.
>
>
>> Second question:
>> My needs is to synchronize network time to the maximum time
>>  of all PCs.

??? what in the world does that mean. 

>> So, if time of PC1 is 10h00min , time of PC2 is 11h00min
>>   and time of PC3 is 12h00min.

Thay will all be false tickers, and ntp will give up. 

>> After started ntp daemon, I would like to have PC1 and PC2
>>  synchronized to PC3 (refid LOOP).
>> I'm wondering if selecting clock based on maximum times
>>  (or offsets) is acceptable.

no. it is not possible. 
>
> I suppose you can modify ntpd, or otherwise influence it
>  (via ntpdc?) by changing prefer(s) however you want.
>
>



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