[ntp:questions] remote NTP server

Steve Kostecke kostecke at ntp.org
Fri Jun 27 22:20:55 UTC 2008

On 2008-06-27, kvdh <kvonderheydt at whoi.edu> wrote:

> RE: ntp serving. How exactly does the server sync to information
> provided by a GPS receiver? Does it simply read the RMC string
> or equivalent on a serial port or does it also use the PPS as in
> interrupt

A timing GPS provides both an NMEA sentence (which labels the seconds)
and a PPS signal (which marks to top of the second, usually within 1us
of UTC).

The ntpd on the server uses both of these pieces of information
to discipline, or steer, the server clock.

> and if the later is necessary, is that received via an SBC's parallel
> port bit.

The Generic NMEA driver reads the PPS signal on the serial port DCD

Other configurations are possible.

> Does the server then make time information available on request?

The ntpd on the server answers polls from other ntpds, and sntp
instances, on the "client" systems.

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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