Time Synchronization in an NT Network

Designing a Time-Synchronized Network
Using these concepts, you can design your time-synchronized NT network. First, study the existing domain structure and physical layout of your network with these questions in mind: Where are the domains? Are they across a WAN link? How many servers are in a domain, and where are they? Which domains do workstations belong to? Then choose a standard time source and define a master time server, primary time servers, and secondary time servers on the network.

Knowing your NT network structure is important when you design an optimal time-synchronized network, because you want to balance the workload on existing and future servers and minimize the impact of time synchronization on network traffic, especially in a WAN environment. A good rule is to keep time acquisition as local as possible, both physically and logically. Physically local means the time source or server is geographically near; logically local means the time source or server is in the same domain or in one that is close.

You can choose a standard time source based on your location or preference. Table 1 lists the standard time sources. In the US, TimeServ supports only NIST and USNO, even though they are not the only time sources. You can contact a time source by modem, or if you have a stable Internet link, you can use it to save telephone charges to a remote time source. If you have a good NTP server on the network, your master time server can obtain network time from the NTP server if you specify NTP as the selected time source and give the NTP server name or IP address in the TimeServ initialization file.

For a small LAN without many servers and workstations in one NT domain, you might not need a primary time server. All secondary time servers and client workstations can obtain network time from one master time source. Figure 2 shows time synchronization in a single-domain network.

For an NT network with multiple domains, the model is the multitiered time synchronization system described earlier. A master time server can reside in corporate headquarters or the corporate MIS department for centralized administration. You can put one or more primary time servers in every domain. Adding this second layer of time servers reduces the workload of the master time server and reduces network traffic because only a limited number of primary time servers talk to the centralized master time server, which might not be in their local network. All remaining servers in every domain are secondary time servers that obtain network time locally from a primary time server in the same domain. Figure 3 shows time synchronization in a multidomain network.

For a very large multidomain network, you can further reduce network traffic if a primary time server in a domain requests the time from another primary time server in a nearby domain. For example, a network has master domains in Chicago, New York, and London. Each master domain has regional resource domains. A master time server is located in the corporate headquarters in Chicago. A primary time server is in each domain. To reduce traffic to the master time server in the headquarters, you can design the primary time server in a resource domain in Chicago, New York, and London to obtain time from the primary time server in its regional master domain. Figure 4 illustrates this process.

Configuring a Time Server
After you design the optimal time synchronization system for your network, you must configure each of your time servers by setting the configuration parameters in a TimeServ initialization file, timeserv.ini. Running the time service execution file, timeserv.exe, saves the settings to the system's Registry.

Listings 1, 2, and 3 show example configuration settings in timeserv.ini for a master time server using a modem, for a primary time server, and for a secondary time server, respectively. The settings answer the following questions:

1. What type is the time server?

The time server can be a master, primary, or secondary time server, as shown in the Type= statement in listings 1, 2, and 3. If a standard time source name, Internet, or NTP appears in the Type=statement, the server is a master time server.