The NTP provider is the standard time provider that is included with Windows Server 2003. The NTP provider in the Windows Time service consists of the following two parts:

• NtpServer output provider.This is a time server that responds to client time requests on the network.
  
  
• NtpClient input provider.This is a time client that obtains time information from another source, either a hardware device or an NTP server, and can return time samples that are useful for synchronizing the local clock.
  
  

Although the actual operations of these two providers are closely related, they appear independent to the time service. By default, when a computer that is running Windows Server 2003 is connected to a network, it is configured as an NTP client.

Communicator Phone Edition searches for a NTP server in DNS as follows:

• NTP SRV record (UDP port 123)
  
  
  • _ntp._udp.<SIP domain> pointing to NTP server
    
    

If it cannot find the NTP SRV record, it will try to use windows.com as an NTP server.

• NTP A record
  
  
  • time.windows.com
    
    

To set Group Policy for Windows Time Service global configuration settings

1. From the MMC, click Active Directory Users and Computers.
   
   
2. Right-click the domain that contains the NTP server, and then select Properties.
   
   
3. Click the Group Policytab, make sure that the Default Domain Policyis highlighted, and then click Edit.
   
   
4. Click Computer Configuration, click Administrative Templates, click System, and then click Windows Time Service.
   
   
5. Click Time Providersand in the right pane, double-click Enable Windows NTP Server, select the Enabledbutton, and then click OK.
   
   
6. From the Group Policy Object Editormenu, select File, and then click Exit.