This article describes the Simple Network Time Protocol (SNTP) time servers that are available on the Internet.
There are two levels, or tiers, of Network Time Protocol (NTP) time servers that are available on the Internet. The NTP is defined in Request for Comments (RFC) 1305.
The first-level time servers are primarily intended to act as source time servers for second-level time servers. The first-level time servers may also be capable of providing mission-critical time services. Some first-level time servers may have a restricted access policy.
Second-level time servers are intended for general SNTP time service needs. Second-level time servers usually enable public access. We recommend that you use second-level time servers for typical SNTP time server configuration because they are usually located on a closer network that can produce faster updates.
We also recommend that you research any time server selection to make sure that it meets your specific time server requirements.
Time server list
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For the list of Stratum One time servers, go to the following website:
Microsoft does not maintain a list of time servers or recommend one time server over another. These links are for your reference and research to select the time servers that are appropriate for your configuration. Microsoft does recommend that workgroup computers sync from the Microsoft NTP server (time.windows.com). If another time source is desired, we recommend that you use one of the Stratum Two time servers. To find the Stratum Two time servers that are available, go to the following website:
Domain-joined member computers and application servers should be configured to synchronize time by using the domain hierarchy that is described in the "Domain Hierarchy-Based Synchronization" topic at the following Microsoft TechNet website:
For more information about how to use time services in Windows Server and Windows NT, click the following article numbers to view the articles in the Microsoft Knowledge Base:
888794 Considerations when hosting Active Directory domain controller in virtual hosting environments
243574 "Could Not Locate a Time Server" After Setting SNTP Time Server Using NET TIME Command
216734 How to configure an authoritative time server in Windows 2000
224799 Basic Operation of the Windows Time Service
951531 The W32Time service does not synchronize the CMOS clock time to the Internet time on a Windows XP or Windows Server 2003-based computer after the W32Time service stops
875495 How to detect and recover from a USN rollback in Windows Server 2003
939322 Support boundary to configure the Windows Time service for high accuracy environments
897615 Support policy for Microsoft software running in non-Microsoft hardware virtualization software
289668 Advancing time on production computers and the effect on Active Directory and FRS
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