[ntp:questions] Poll timing

Steve Kostecke kostecke at ntp.org
Fri Aug 17 02:56:28 UTC 2007

On 2007-08-16, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:

> Steve Kostecke wrote:
>> On 2007-08-16, Jussi Kauppinen <jtkauppi at cc.hut.fi> wrote:
>>>I'm developing a system that utilize NTP. Unfortunately, the details
>>>of the system are confidential. For this system to work properly,
>>>it is essential that polling phase inside a second is approximately
>>>constant related to the clock of the client,
>> The exact poll timing is irrelevant as far as NTP is concerned.
>> The Unicast (i.e. client/server) polling scheme time-stamps the
>> packet when it is sent from the "client", at the "server", and
>> again when it arrives back at the "client".
> I believe that the packet is timestamped TWICE by the server; once
> when it arrives and again when the response is returned. These two
> would normally be very close to each other

Four time-stamps sounds correct.

But the key point here is not the exact number of time stamps. It is
that the time of the poll occurance is not fixed; time stamps that are
added to the NTP packet at the client and the server are used by the
client ntpd to determine the time.

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

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