Re: Synchronizing to LOCAL(0): Startup time

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 192.168.1.80 iburst burst prefer minpoll 4 maxpoll 4 prefer
peer 192.168.1.98 iburst burst prefer minpoll 4 maxpoll 4 prefer
peer 192.168.1.162 iburst burst prefer minpoll 4 maxpoll 4
server 127.127.1.0 iburst # local clock (LCL)
fudge 127.127.1.0 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.

Danny
.

Relevant Pages

  • Re: ntpd just sits there and does nothing
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  • Re: NTP in a Linux cluster
    ... I don't know if servers or peers can be given their own minpoll and maxpoll. ... I have found that, for me, having the fixed smaller values on local LAN servers produces lower offsets, although that was not on Linux systems. ... On two of my systems which peer with each other I have: ...
    (comp.protocols.time.ntp)
  • Re: ntpd losing sync
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    (comp.protocols.time.ntp)
  • Re: symmetric-active mode (peer) and autokey
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  • Peering amongst S1
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