NTP Configuration with Meinberg Driver Package for Windows

By default, the NTP program ntpd works both as client and server at the same time.

In the role of a client it gets the reference time from some other configured server or reference clock, and adjusts its own system time towards the reference time.

In the role of a server it makes the system time available to other NTP clients.

If a Meinberg PCI card or USB device has been installed, the machine can be configured to act as a top-level (stratum-1) NTP server for clients on the network.

First the Meinberg Driver Software Package should be installed, which makes the PCI card or USB device accessible from applications. The driver package includes the Meinberg Time Adjustment Service which reads the time from the PCI card once per second and adjusts the Windows system time smoothly to the time from the PCI card or USB device.

The NTP software package should be installed after the Meinberg Driver Software Package. The setup program detects the presence of the Meinberg time adjustment service and suggests to create an NTP configuration labelled Follow Meinberg time service.

This means that the NTP service (ntpd) on this machine must not adjust the system time on this computer since this is already done by the Meinberg time adjustment service. The only task of the ntpd instance on this machine is to make the disciplined time available on the network for other NTP clients.

The relevant lines in the configuration file ntp.conf are:

# your local system clock, adjusted by the Meinberg Time Service
server 127.127.1.0
# It operates at stratum level 0
fudge 127.127.1.0 stratum 0
fudge 127.127.1.0 refid LCL0

Please note the IP address 127.127.1.0 used above is a well-known, specific pseudo-IP address used by ntpd. It does not refer to localhost (127.0.0.1) and thus must not be replaced with some other number.

The NTP setup programs also puts some restrict lines into the NTP configuration file to increase the security of this setup.

Please note that no driftfile must be specified in this case. Using a driftfile makes no sense in this case because ntpd must not apply any adjustment to the Windows system time. However, if a drift file was found the a default adjustment from that file would be applied by ntpd, which could badly interfere with the time adjustment made by the Meinberg time adjustment service.

If some other remote time server and/or a driftfile is specified in ntp.conf, the monitor program from the Meinberg driver package (mbgmon.exe) may display a warning from the Meinberg time adjustment service that The system time is changed by another program, because ntpd also fiddles with the system time.

Please note also that it make no sense to install and use use the Meinberg NTP Time Server Monitor for Windows on the time server because

• it can easily be used to unintentionally and inappropriately change the ntp.conf file
• the NTP service in this application does not generate any statistics files that can be visualized by the program

Usage of the Meinberg NTP Time Server Monitor for Windows only makes sense if the NTP service is also configured to adjust the system time, e.g. on clients that run ntpd.

Acting as a client means the NTP service tries to poll (query the time from) one or more NTP servers on the network, and adjusts the system time according to the time from the remote server(s).

For each NTP server to be polled a line like the following is basically sufficient:

server aa.bb.cc.dd iburst minpoll 6 maxpoll 6

where aa.bb.cc.dd has to be replaced with the IP address or DNS hostname of the remote NTP server.

The iburst keyword speeds up initial synchronization with the server.

Due to specific limitations in Windows, the minpoll 6 maxpoll 6 keywords are particularly important under Windows.

For this mode of operation, only the NTP software package needs to be installed. The Meinberg driver software package for Windows is not required.

If you run the Meinberg NTP installer under Windows and the setup program does not detect the presence of the driver package, you can enter the IP address of one or more NTP servers on the network directly during setup. The setup program then generates a configuration file with appropriate server lines as shown above.

The NTP setup programs also puts some restrict lines into the NTP configuration file to increase the security of this setup.

It also adds an entry for a driftfile in this case. The driftfile is used by ntpd to save the last known clock drift compensation value across reboots and service restarts, to speed up initial synchronization.

— Martin Burnicki martin.burnicki@meinberg.de, last updated 2023-07-06