Synching to an External Time Source
If you want to ensure that the clocks on your machines are more
accurate in terms of absolute (and not just relative) time, you can
sync the PDC Emulator in your forest root domain to one of the reliable
time servers available on the Internet. This is a good idea if your
company is a large enterprise with sites spanning several countries, or
if your organization has two or more forests linked by forest trusts.
The procedure for doing this on a PDC Emulator running Windows Server
2003 in the forest root domain is as follows. Open Registry Editor
(regedit.exe) and configure the following registry entries:
HKLMSYSTEMCurrentControlSetServicesW32TimeParametersType
This registry entry determines which peers W32Time will accept synchronization from. Change this REG_SZ value from NT5DS to NTP
so the PDC Emulator synchronizes from the list of reliable time servers
specified in the NtpServer registry entry described below.
HKLMSYSTEMCurrentControlSetServicesW32TimeConfigAnnounceFlags
This registry entry controls whether the local computer is marked as
a reliable time server (which is only possible if the previous registry
entry is set to NTP as described above). Change this REG_DWORD value
from 10 to 5 here.
HKLMSYSTEMCurrentControlSetServicesW32TimeParametersNtpServer
This registry entry specifies a space-delimited list of stratum 1
time servers from which the local computer can obtain reliable time
stamps. The list may consist of one or more DNS names or IP addresses
(if DNS names are used then you must append ,0x1 to the end of
each DNS name). For example, to synchronize the PDC Emulator in your
forest root domain with tock.usno.navy.mil, an open-access SNTP time
server run by the United States Naval Observatory, change the value of
the NtpServer registry entry from time.microsoft.com,0x1 to tock.usno.navy.mil,0x1 here. Alternatively, you can specify the IP address of this time server, which is 192.5.41.209 instead.
Now stop and restart the Windows Time service using the following commands:
net stop w32time
net start w32time
It may take an hour or so for the PDC Emulator to fully synchronize
with the external time server because of the nature of the polling
method W32Time uses. Depending on the latency of your Internet
connection, the accuracy of the CMOS clock on your forest root PDC
Emulator may be within a second or two of UTC. If you need more
accurate time however, you can purchase a hardware time source like an
atomic clock and connect it to your PDC emulator.
Alternatively, if you don’t want to wait for time convergence to
occur between your stratum 2 time server (your forest root PDC
Emulator) and the external stratum 1 time server, you can run the
following command on your PDC Emulator:
w32tm /resync /rediscover
Tip
There are additional registry settings you can configure to ensure external time synchronization operates effectively, see http://support.microsoft.com/kb/816042 in the Microsoft Knowledge Base for details.