[This is pre-release documentation and subject to change in future releases. This topic's current status is: Milestone-Ready]

Topic Last Modified: 2010-07-15

Network Time Protocol (NTP) is the default time synchronization protocol used by the Windows Time Service in Windows Server. NTP is a fault-tolerant, highly scalable time protocol and is the protocol used most often for synchronizing computer clocks by using a designated time reference. Microsoft Communicator “14” Phone Edition requires NTP to set the correct time and date for Communicator “14” Phone Edition.

NTP Time Provider

The NTP provider is the standard time provider included with Windows Server. 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 is connected to a network, it is configured as an NTP client.

Communicator “14” Phone Edition searches for a NTP Server in DNS:

  • NTP SRV record (UDP port 123)

  • _ntp._udp.<SIP domain> pointing to NTP Server

If it cannot find the NTP SRV record it will attempt to use http://time.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 your NTP Server, and selects Properties.

  3. Click the Group Policy tab, make sure the Default Domain Policy is highlighted and click Edit.

  4. Click Computer Configuration, click Administrative Templates, click System, and then click Windows Time Service.

  5. Click Time Providers and in the right pane double-click Enable Windows NTP Server, select the Enabled button and click OK.

  6. From the Group Policy Object Editor menu select File and click Exit