[ntp:questions] NTP daemon - fixed offset against real time

Unruh unruh-spam at physics.ubc.ca
Sat Jan 26 22:16:12 UTC 2008

David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:

>msmucr at gmail.com wrote:
>> i would like to ask you for help or ideas with one ntp related task.
>> I need to setup one ntp server to serve its sntp clients
>> with time, which is specific amount of time (several seconds) in

>You would need to modify the source code to do that.  If you do so, 
>please also overwrite the stratum, reported to clients, with 15, so that 
>if anyone else does try to use you as a server, they won't be able to 
>further distribute broken time.  (It may also be possible to set a silly 
>root dispersion, if the SNTP clients are not too fussy about it, to 
>completely stop NTP clients using the server adding your time offset to 
>root dispersion would be reasonably honest, as long as it is more then 
>one second.)

I would think it would be both easier and much less prone to introducing
bugs if theprogram running TV stuff added on the offset. Come two years
from now you will forget that the time on the machines is munged time, and
use it as real time. 

\on \Linux you could probably define a special timezone which was x seconds
off UTC. 
The refclocks off course have the offset option on some of them-- I do not
think it limits you as to how big that could be-- ie get a GPS source, use
the NMEA as a clock, and put in the appropriate offset.

>> advance against correct real time taken from another ntp server in
>> network. I did some search in documentation from both ntpd and
>> openntpd, but i didn't find any configuraition option related to this.

>One wouldn't expect the facility to deliberately break them in this way.

>> I need this quirky thing due to time syncing of several broadcast
>> graphics servers which also generates clocks to TV picture and it is
>> necessary to compensate delay caused by MPEG coding and transmission
>> of TV signal.

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