NTP Time server ..setup is this needed?????

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Hi, all
I am trying to decipher why would one chose to synchronizes time using a
dedicated NTP server rather than using the domain hierarchy . Currently my
root PDC emulator uses an external time source and as a result my clients
(XP and Win2000) desktops PC's and member servers will use the DC/PDC
emulator. I do understand how this all works ,but why or when would it be
best to use a dedicated NTP server. ???

The reason I ask is because we have recently aquired another company and
I've noticed they are using a dedicated time server which happens to be one
of the DC in that domain . In addtion, I did notice within serveral GPO's
the policy (System/Windows Time Service/Time Providers) is enabled, which
would result for all clients being redirected to this NTP (DC)

TIA


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