[ntp:questions] Re: Freeware for NTP time synchronization under Windows?

Steve Kostecke kostecke at ntp.isc.org
Tue Oct 19 13:21:43 UTC 2004

On 2004-10-19, Tapio Sokura <oh2kku at iki.fi> wrote:

> David Woolley wrote:
>> "Chaos Master" wrote:
>>>I am looking for a freeware Windows program to synchronize PC' clock
>>>over the nternet, using the NTP (Network Time Protocol) protocol
>> What do you mean by Windows? For any Windows system bought new
>> in the last two or three years, you should use the reference NTP
>> implementation,
> There is at least one problem with using ntpd (as in www.ntp.org)
> especially in laptops and other computers that are not always
> connected to an IP-network and/or change IP-addresses frequently.
> Because ntpd expects to always have network connectivity

ntpd is intended to be used in conjunction with a source of time (e.g. a
local reference clock, remote time servers).

> [ntpd] doesn't handle IP addresses changing under it while it is
> running,

It is true that ntpd does not currently detect interface address
changes. One solution, which is trivial to implement on an OS which
provides decent scripting facilities, is to this is to restart ntpd when
your interface address changes.

> In my opinion if the user enters a DNS name for the NTP server
> address, the client should automatically re-resolve the name every
> time the client software is started/first queries a server. Resolving
> the server name before sending each individual query could result in
> needless clockhopping.

This is exactly what ntpd does; all DNS queries are performed at

> What I meant to say is this: ntpd is excellent for servers and
> workstations that are always connected to an IP network with a stable
> IP address, but not optimal for "road warriors".

ntpd may not be the best solution for everyone. But there is no
requirement that you have a static IP address to use it. With a bit of
work you can use ntpd on systems with dynamic IP addresses, too.

Steve Kostecke <kostecke at ntp.isc.org>

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