NTP 4.x for Windows NT

Do not try to compile NTP-4.0.99i under WINNT, it will not work. Fixed NTP-4.0.99i; look for next release to be functional. Sven - May 11 2000

Download NTP-4.0.99g for the last stable WINNT port. I am working on adapting the major changes starting with 99i and getting things running again. Sven - April 25 2000


The NTP 4 distribution runs as service on (i386) Windows NT 4.0 and Windows 2000. The binaries work on dual processor systems. This port has not been tested on the Alpha platform.

Refer to System Requirements and Instructions for how to compile the program.

Reference Clocks

Refernce clock support under Windows NT is tricky because the IO functions are so much different. The following reference clocks are supported by Windows NT:

Type 1 Undisciplined Local Clock (LOCAL)
Type 29 Trimble Navigation Palisade GPS (GPS_PALISADE)

Functions Supported

All NTP functions are supported with some constraints. See the TODO list below.


Greg Brackley has implemented a fantastic interpolation scheme that improves the precision of the NTP clock using a realtime thread (is that poetic or what!) which captures a tick count from the 8253 counter after each OS tick. The count is used to interpolate the time between operating system ticks.

On a typical 200+ MHz system NTP achieves a precision of about 5 microseconds and synchronizes the clock to +/-500 microseconds using the Trimble Palisade as UTC reference. This allows distributed applications to use the 10 milliseconds ticks available to them with high confidence.


Recent InstallShield based executable versions of NTP for Windows NT (i386) are available from:
http://www.trimble.com/oem/ntp and http://www.five-ten-sg.com/


Compiling Requirements

Compiling Instructions

  1. Unpack the NTP-4.x.tar.gz
  2. Open the .\ports\winnt\ntp.dsw Visual C workspace
  3. Batch build all projects

Configuration File

The default NTP configuration file path is %SystemRoot%\system32\drivers\etc\. (%SystemRoot% is an environmental variable that can be determined by typing "set" at the "Command Prompt" or from the "System" icon in the "Control Panel").
Refer to your system environment and create your ntp.conf file in the directory corresponding to your system  installation.
The older <WINDIR>\ntp.conf is still supported but you will get a log entry reporting that the first file wasn't found.

Installation Instructions

The instsrv program in the instsrv subdirectory of the distribution can be used to install 'ntpd' as a service and start automatically at boot time. Instsrv is automatically compiled with the rest of the distribution if you followed the steps above.
  1. Start a command prompt and enter "instsrv.exe <pathname_for_ntpd.exe>"
  2. Clicking on the "Services" icon in the "Control Panel" will display the list of currently installed services in a dialog box. The NetworkTimeProtocol service should show up in this list. Select it in the list and hit the "Start" button in the dialog box. The NTP service should start.
  3. View the event log by clicking on the "Event Viewer" icon in the "Administrative Tools" group, there should be several successful startup messages from NTP. NTP will keep running and restart automatically when the machine is rebooted.
You can change the start mode (automatic/manual) and other startup parameters correponding to the NTP service (eg. location of conf file) also in the "Services" dialog box if you wish.

Removing NTP

You can also use instsrv to delete the NTP service by entering: "instsrv.exe remove"

Command Line Parameters and Registry Entries

Unlike the Unix environment, there is no clean way to run 'ntpdate' and reset the clock before starting 'ntpd' at boot time.
NTP will step the clock up to 1000 seconds by default. While there is no reason that the system clock should be that much off during bootup if 'ntpd' was running before, you may wish to override this default and/or pass other command line directives.

Use the registry editor to edit the value for the ntpd executable under LocalMachine\System\CurrentControlSet\Services\NTP.

Add the -g option to the ImagePath key, behind "%INSTALLDIR>\ntpd.exe". This will force NTP to accept large time errors (including 1.1.1980 00:00)

Bug Reports

Send bug reports to news://comp.protocols.time.ntp and Sven_Dietrich@Trimble.COM

Change Log

Last revision 16 February 1999  Version 4.0.99e.

by Sven Dietrich (sven_dietrich@trimble.com)

Significant Changes:

Last revision 15 November 1999  Version 4.0.98f.

by Sven Dietrich (sven_dietrich@trimble.com)

Significant Changes:

Known Problems / TODO:

Last revision 27 July 1999  Version 4.0.95.

This version compiles under WINNT with Visual C 6.0.

Greg Brackley and Sven Dietrich

Significant changes:
-Visual Studio v6.0 support
-Winsock 2.0 support
-Use of I/O completion ports for sockets and comm port I/O
-Removed the use of multimedia timers (from ntpd, others need removing)
-Use of waitable timers (with user mode APC) and performance counters to fake getting a better time
-Trimble Palisade NTP Reference Clock support
-General cleanup, prototyping of functions
-Moved receiver buffer code to a separate module (removed unused members from the recvbuff struct)
-Moved io signal code to a separate module

Last revision:  20-Oct-1996

This version corrects problems with building the XNTP
version 3.5-86 distribution under Windows NT.

The following files were modified:
 html\hints\winnt (this file)

In order to build the entire Windows NT distribution you
need to modify the file scripts\wininstall\build.bat
with the installation directory of the InstallShield
software.  Then, simply type "bldrel" for non-debug
or "blddbg" for debug executables.

Greg Schueman

Last revision:  07-May-1996

This set of changes fixes all known bugs, and it includes
several major enhancements.

Many changes have been made both to the build environment as
well as the code.  There is no longer an ntp.mak file, instead
there is a buildntall.bat file that will build the entire
release in one shot.  The batch file requires Perl.  Perl
is easily available from the NT Resource Kit or on the Net.

The multiple interface support was adapted from Larry Kahn's
work on the BIND NT port.  I have not been able to test it
adequately as I only have NT servers with one network
interfaces on which to test.

* Event Logging now works correctly.
* Version numbers now work (requires Perl during build)
* Support for multiple network interface cards (untested)
* NTP.CONF now default, but supports ntp.ini if not found
* Installation procedure automated.
* All paths now allow environment variables such as %windir%

Bug fixes:
* INSTSRV replaced, works correctly
* Cleaned up many warnings
* Corrected use of an uninitialized variable in XNTPD
* Fixed ntpdate -b option
* Fixed ntpdate to accept names as well as IP addresses
        (Winsock WSAStartup was called after a gethostbyname())
* Fixed problem with "longjmp" in xntpdc/ntpdc.c that
        caused a software exception on doing a Control-C in xntpdc.
 A Cntrl-C now terminates the program.

See below for more detail:

      Note: SIGINT is not supported for any Win32 application including
      Windows NT and Windows 95. When a CTRL+C interrupt occurs, Win32
      operating systems generate a new thread to specifically handle that
      interrupt. This can cause a single-thread application such as UNIX,
      to become multithreaded, resulting in unexpected behavior.

Possible enhancements and things left to do:
* Reference clock drivers for NT (at least Local Clock support)
* Control Panel Applet
* InstallShield based installation, like NT BIND has
* Integration with NT Performance Monitor
* SNMP integration
* Fully test multiple interface support

Known problems:
*       bug in ntptrace - if no Stratum 1 servers are available,
                such as on an IntraNet, the application crashes.

Last revision:  12-Apr-1995

This NTPv3 distribution includes a sample configuration file and the project
makefiles for WindowsNT 3.5 platform using Microsoft Visual C++ 2.0 compiler.
Also included is a small routine to install the NTP daemon as a "service"
on a WindowsNT box. Besides xntpd, the utilities that have been ported are
ntpdate and xntpdc. The port to WindowsNT 3.5 has been tested using a Bancomm
TimeServe2000 GPS receiver clock that acts as a strata 1 NTP server with no
authentication (it has not been tested with any refclock drivers compiled in).
Following are the known flaws in this port:
1) currently, I do not know of a way in NT to get information about multiple
   network interface cards. The current port uses just one socket bound to
   INADDR_ANY address. Therefore when dealing with a multihomed NT time server,
   clients should point to the default address on the server (otherwise the
   reply is not guaranteed to come from the same interface to which the
   request was sent). Working with Microsoft to get this resolved.
2) There is some problem with "longjmp" in xntpdc/ntpdc.c that causes a
   software exception on doing a Control-C in xntpdc. Be patient!
3) The error messages logged by xntpd currently contain only the numerical
   error code. Corresponding error message string has to be looked up in
   "Books Online" on Visual C++ 2.0 under the topic "Numerical List of Error

Last HTML Update: November 17, 1999