[ntp:questions] Re: NTP on laptop?

David Woolley david at djwhome.demon.co.uk
Wed Mar 8 07:12:52 UTC 2006

In article <dul22k$kld$1 at rumours.uwaterloo.ca>,
dj3vande at csclub.uwaterloo.ca (Dave Vandervies) wrote:

> How friendly is ntpd to typical laptop network connection habits?

ntpd is not laptop friendly.

> If I just leave ntpd running with a ntp.conf that points it at network
> servers along with the local clock, will it talk to the servers when
> they're reachable and run off of the local clock when they aren't?

It will coast with the the last known frequency correction whether
or not the the local clock is configured, so you should not configure
the local clock unless you really understand what it does.  Basically,
leaf nodes never need the local clock configuring as a source.

However the NTP protocol doesn't like intermittent network connections
and ntpd doesn't like dynamic IP addresses or power management of
CPU clock frequencies.

> If it won't notice on its own when network connection status changes,
> will it be enough to swap different versions of ntp.conf in and out in

ntpd never rescans the configuration file.   It can be used with 
static addresses and dynamic connections provided that the interface
is demand dial and appears permanently up.  With good demand dial 
software (recently looking at RRAS on Windows suggests that it is
not "good") you can have bringup filters that will permit NTP traffic
when the PPP connection is up, but not bring up the connection in 
response to it.

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