[ntp:questions] Question about the use of broadcast

David Woolley david at ex.djwhome.demon.invalid
Tue Apr 19 21:04:29 UTC 2011


Yann I. wrote:

> 
> For information :
>  - The servers "SRV NTP 01a" and "SRV NTP 01b" can't communicate. Idem

There is no solution possible as there is nothing to constrain the times 
  seen by the 03 level to have overlapping confidence intervals.  For 
this to stand any chance of working, server 01a and b need to be 
synchronised, quite accurately, as this is a LAN, to a common time 
standard.  The preferred one is always UTC, from a radio clock.

> for the servers "SRV NTP 02a" and "SRV NTP 02b",
>  - The link between "SRV NTP 01" and "SRV NTP 02" is a bidirectionnal
> link,
>  - The link between "SRV NTP 02" and "SRV NTP 01" is an
> unidirectionnal link and only UDP datagrams can be used (TCP is not
> allowed).

This sort of question needs to be solved at the real problem definition 
level, not at a sub-problem level with lots of arbitrary constraints.  I 
would have said this was homework, except that the constraints are just 
to contorted for homework.

>  - Why is the server which have the lowest stratum is not the
> reference ? As you can see, this is always the "LOCAL(0)" which is the
> reference.

Probably because it has been thrown out as a false ticker, because you 
have non-overlapping confidence intervals.  That is typically how local 
clock arrays break.

>  - When I start the server "SRV NTP 02b", the server "SRV NTP 03" saw
> them as untrusted (marked with a 'x'). What's wrong ? Should I use a
> key or something like that ?

That will definitely be because of the conflicting confidence intervals.

You need to run assoc and then rv on the association IDs to find out the 
exact reject reasons.

> NTP 03" can "see" the two sources but after 10 minutes, the ntpd
> daemon (of "SRV NTP 03") crashes... Maybe should I update the server
> ntpd ?

Do you really mean crash?  You should update, as no bug report will be 
considered on that version.




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