NTP Server Configuration

The Network Time Protocol (NTP) is a standard for synchronizing computer system clocks over package-based communication networks. Although this is usually done by means of UDP, it can also be transported by other Layer 4 protocols such as TCP, for example. It was specially developed to enable reliable time relaying over networks with variable package runtimes. 

To configure the Windows Time service to use an internal hardware clock yourself, you can change the announce flag on the authoritative time server. Changing the announce flag forces the computer to announce itself as a reliable time source and to use the built-in complementary metal oxide semiconductor (CMOS) clock. 

To configure the Windows Time service to use an internal hardware clock, follow these steps.

1. Enable NTP Server.
Click Start, click Run, type regedit, and then click OK.

2. Locate and then click the following registry subkey: 
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpServer

In the pane on the right, right-click Enabled, and then click Modify .In Edit DWORD Value, type 1 in the Value data box, and then click OK.

3. Set AnnounceFlags to 5. 
Locate and then click the following registry subkey: 
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags

In the pane on the right, right-click AnnounceFlags, and then click Modify. In Edit DWORD Value, type 5 in the Value data box, and then click OK.

4. Change the server type to NTP.
Locate and then click the following registry subkey: 
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\Type

In the pane on the right, right-click Type, and then click Modify. In Edit Value, type NTP for WindowsXP,Windows7 or NT5DS for Windows Server in the Value data box, and then click OK.

5. Exit Registry Editor and restart the Windows Time service.
At the command prompt, type the following command to restart the Windows Time service, and then press Enter:
net stop w32time && net start w32time

Reference

How to Setup a Windows 2008 R2 SNTP/NTP Server
http://bchavez.bitarmory.com/archive/20 ... erver.aspx

How to configure an authoritative time server in Windows XP
http://support.microsoft.com/kb/314054

How to configure an authoritative time server in Windows Server
http://support.microsoft.com/kb/816042

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
How to back up and restore the registry in Windows
http://support.microsoft.com/kb/322756

Tips

- Make sure W32Time is set to Automatic startup mode.

- Make sure UDP 123 is allowed through your firewall.

- Use this InternetTime program to help you checking connectivity toNTP server.
internettime.zip

 internettime.zip