[ntp:questions] NTPD sync now

David L. Mills mills at udel.edu
Fri Nov 3 00:18:47 UTC 2006


In a lot of telcos today long distance dialing is free or almost free. 
You might consider ACTS/USNO as I do in my campus office. The ntpd calls 
every 36 hours and keeps the clock generally within 50 ms.

The expectation in the ntpd design is that the router, upon receiving a 
NTP packet, would initiate the ISP lease, burst eight packets, update 
the clock and expect the router to time out the call. The burst program 
can be tinkered for an initial poll interval whatever it takes for the 
line to become hot, then finish up at two-second intervals. Clever 
adjustments for minpoll, maxpoll and the router timeout should cover 
most cases.


David Woolley wrote:
> In article <3ltp14-tse.ln1 at robert.houseofmax.de>,
> Uwe Klein <uwe_klein_habertwedt at t-online.de> wrote:
>>what irks me is that ntp allways creates extra slots in between.
> That's a problem with your demand dial software.  You should use software
> that you can configure to transmit NTP when the link is up but not bring
> it up for NTP, nor keep it up for NTP.  (Good demand dial software will
> also do things like varying the timeout depending on the type of packet
> and whether there are open TCP connections.)
> Alternatively, you can, but only after getting explicit permission
> from the people who operate your servers (you will probably find this
> limits you to your ISP and your own company), use the burst option,
> which should try enough polls with enough gaps to ensure that the later
> polls get through.  Using burst without permission is considered as
> serious abuse and may get you blocked by the server.
> Generally, though, ntpd and demand dial don't go together particularly
> well.

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