FYI...these links should answer all of your questions and more
setting authorative time server
W32time registry entries
basic operation of the time service
This is copied from the W32Time whitepaper because i couldnt find the link for it on the web
Time Convergence
Time convergence occurs throughout a network as each computer accesses time from a more reliable time server. A client issues a request to a time server for synchronization using the client computer's Relative ID (RID). The time server determines the secret password for the client's RID, and this password is renegotiated every 30 days between each computer and the Active Directory domain. The reliable server sends the current time the computer in the clear in the form of a signed SNTP packet. When the client receives the packet, it verifies its integrity and that the source of the packet is the requested time server. The information provided within the packet determines whether an adjustment needs to be made to the computer's current clock time so that it becomes synchronized with the more reliable server. If the client determines that the packet is intact, it synchronizes its time with the server.
To determine the actual local time, the local clock offset is calculated according to this standard SNTP equation:
LocalClockOffset=((ReceiveTimestamp-OriginateTimestamp)+
(TransmitTimestamp-DestinationTimestamp))/2
Note This equation is from RFC 1769. It takes into account network delays and assumes that they are symmetrical.
Each of the following variables are specified within the SNTP packet:
· ReceiveTimestamp is the local time at which the server receives the latest time request from the client.
· OriginateTimestamp is the local time at which the client sends its latest time request.
· TransmitTimestamp is the local time at which the server sends the time reply.
· DestinationTimestamp is the local time at which the client receives the time reply.
Many factors go into determining whether or not an SNTP packet is valid and whether or not it will be accepted for time synchronization. These factors include:
· Packet size and the fields within the packet that can indicate loss of synchronization (see RFC 1769 for a detailed description of SNTP packet format).
· Verification that the current response is a response to the last request made by the client.
· Verification that the year is greater than or equal to 1995. (This date holds no particular significance.)
If a packet does not meet the preceding qualifications, the packet is disregarded and time is not synchronized.
When the local clock offset has been determined, the following algorithm is used to adjust the time:
· If the local clock time of the client is behind the current time received from the server, W32Time will change the local clock time immediately.
· If the local clock time of the client is more than three minutes ahead of the time on the server, W32Time will change the local clock time immediately.
· If the local clock time of the client is less than three minutes ahead of the time on the server, W32Time will quarter or halve the clock frequency for long enough to bring the clocks into sync. If the client is less that 15 seconds ahead, it will halve the frequency; otherwise, it will quarter the frequency. The amount of time the clock spends running at an unusual frequency depends on the size of the offset that is being corrected.
The Basic Time Synchronization process is illustrated in Figure 1 below.
W32Time will periodically check its local time with the current time by connecting to the time source, usually the authenticating domain controller. This process starts as soon as the service turns on during system startup. W32Time attempts synchronization every 45 minutes until the clocks have successfully synchronized three times. When the clocks are correctly synchronized, W32Time then synchronizes at eight-hour intervals, unless there is a failure to obtain a timestamp, or a validation failure. If there is a failure, the process starts over from the beginning.
The result is that all computers within the enterprise running W32Time reliably converge to a common time.
Time Convergence Hierarchy
To synchronize computers on a Windows 2000 network, W32Time must have a reliable time source from which to sync. W32Time can be configured to use one of three methods for synchronization by modifying entries in the registry (see "W32Time Registry Entries" later in this article). These methods are domain hierarchy based synchronization, using a manually specified synchronization source, or using no synchronization at all. Domain hierarchy based synchronization is the default on every Windows 2000–based computer, and meets the time synchronization requirements specified by the Kerberos V5 protocol. The accuracy of a time server is indicated by a number called the stratum, with the most accurate time server located at stratum one and each level downward in the hierarchy a number one greater than the preceding level. In a Windows 2000 forest, the stratum number of a local computer is determined by how many hops away it is from the external and most accurate time source.
Domain Hierarchy Based Synchronization
Domain hierarchy based synchronization uses the hierarchy of Active Directory, the directory service included with Windows 2000. In domain hierarchy based synchronization, the Flexible Single-Master Operation of the primary domain controller emulator (PDC emulator) is located in the forest root domain and is connected to an external time source. The external time source holds the position of greatest accuracy, or stratum one. The PDC emulator is at stratum two. The forest root domain can also be called the parent domain, and each domain under the parent or forest root can be called a child domain. Any domain controller that accesses time directly from the PDC emulator of the forest root domain is designated as stratum three. As the stratum increases from one, the achievable accuracies degrade depending on the network paths and local clock stabilities. Figure 2 illustrates the hierarchical relationship between computers in a forest.
