[ntp:questions] Synchronizing to LOCAL(0): Startup time

Danny Mayer mayer at ntp.isc.org
Sun Oct 14 21:46:50 UTC 2007

Bert Gøtterup Petersen wrote:
> Dear all
> I am trying to use NTP to synchronize embedded audio-video products 
> (running Linux).
> Once the products are synchronized everything is working very well, but I 
> have a problem at start up.
> I use a set of products to work as peers, as can be see in the example of 
> an ntp.config file:
> peer  iburst burst prefer minpoll 4 maxpoll 4 prefer
> peer  iburst burst prefer minpoll 4 maxpoll 4 prefer
> peer iburst burst prefer minpoll 4 maxpoll 4
> server iburst # local clock (LCL)
> fudge stratum 6 # LCL is unsynchronized flag1 0 flag2 0 flag3 
> 0 flag4 0 stratum 0

Use burst or iburst but not both together. You should use not burst
under normal circumstances. The addition of minpoll and maxpoll just
makes the situation worse. I always tell people that they should not be
allowed to change the default value of minpoll and maxpoll unless they
have taken a Master's level course from Dave Mills, gotten and A+ and
thoroughly understand how ntpd works. Don't do it. Most of the
algorithms work best when the poll values are left alone.

The normal stratum for the local clock is 10 and not 6 and iburst has no
affect on a local clock: It's not querying anything.

Be aware that Linux has been known to drop interrupts causing issues
with the proper operation of ntpd. This is even more likely to happen
with audio-visual media which also demand real-time responses from the
apps running them.


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