Domain master browser traffic. In addition to compiling a definitive list of all the servers in its domain, a domain master browser is responsible for discovering the names of other domains and workgroups on the network and announcing its domain to other domain master browsers. The domain master browser downloads a list of domains and workgroups called the domain list from its WINS server. The domain master browser sends directed DomainAnnounce messages to the domain master browser of each of the domains and workgroups on the domain list. The master browser uses the DomainAnnounce messages it receives from other domain master browsers to add the names of the network's other domains and workgroups to the master server list, which it passes to its subnets' master browsers. A domain master browser's default domain announcement period is 12 minutes. To change this period, you create and adjust the MasterPeriodicity value on a domain master browser. If you are in the habit of leaving your domain master browser running (this habit is usually a good idea), you can increase your domain master browsers' MasterPeriodicity value to reduce interdomain traffic.
An important optimization is selecting which computers participate in providing the network's browsing service. A process known as election chooses both the domain master browser and master browsers. A domain's PDC automatically assumes the role of domain master browser and master browser for its subnet. By default, if the PDC is offline, NT chooses a master browser based on each computer's OS. A similar process takes place on each subnet to select the master browser. You can rig these elections by setting the IsDomainMaster value in a computer's HKEY_LOCAL_MACHINE\ SYSTEM\CurrentControlSet\ Services\Browser\Parameters Registry key to YES. If a computer's IsDomainMaster value is YES, that computer becomes the master browser for its subnet. Choosing each subnet's master browser rather than leaving master browser selection to the election process is often a good idea, because the Browser service consumes processing and networking resources on master browsers.
Backup browser traffic. Backup browser traffic is the final part of the Browser service's network traffic. When a client needs to browse the network, it contacts a backup browser on its network segment. Each master browser acts as a backup browser, and master browsers appoint as many as three backup browsers—one for every 32 clients—to provide the server list to clients. After a master browser receives the master server list from its domain master browser, it passes the list to the other backup browsers on its subnet.
Backup browsers periodically contact their master browser to obtain a new server list. By default, each backup browser sends this update message every 15 minutes. If your server list is fairly stable—in other words, if you leave your servers on—you might want to increase this interval by creating a BackupPeriodicity entry (of type REG_DWORD) in the HKEY_LOCAL_MACHINE\SYSTEM\ CurrentControlSet\ Services\Browser\Parameters key on your backup browsers and specifying an interval in seconds.
Just as you can select a network's master browsers, you can choose which servers a master browser makes its backup browsers. Rather than leaving the master browser to its own devices, you can set the MaintainServerList value (of type REG_DWORD) under the Browser\Parameters key to YES to make a computer a backup browser. You can set MaintainServerList to NO to ensure that the machine doesn't become a backup browser. The default setting, AUTO, lets the master browser appoint the computer as a backup browser if necessary. Don't make too many computers backup browsers, or you'll create unnecessary synchronization traffic from the master browser.
Unfortunately, you can't control the network traffic between client machines and backup browsers. The first time a client browses, it obtains a list of backup browsers from the master browser of its subnet. The client randomly selects a backup browser from the master browser's list, connects to the backup browser, and requests a copy of the server list. From that moment on, the client goes to that backup browser and downloads the server list whenever the user browses the network. No Registry tweaks can change the frequency of this traffic between clients and backup browsers, because this traffic occurs in realtime whenever the user attempts to browse the network.
Benefit from Reduced Network Traffic
After you make these Registry changes, the background traffic that is essential to every NT network will consume fewer processing and network resources than before. However, don't make these changes without proper planning; make Registry changes only very carefully. In addition, keep in mind that none of the changes I've described take effect until you reboot the system, so you might want to schedule your optimization tasks for a time that minimizes the effect on your network of taking each server offline temporarily. For more detailed information about these Registry changes, see the Microsoft Windows NT Server 4.0 Resource Kit's Windows NT Server Networking Guide and Registry entry documentation or invest in one of the many books about the NT Registry.