The browser service must be notified by a resource when the resource is available for use on the network. When a network computer running Windows 2000, Windows NT, Windows for Workgroups, Windows 95, or Windows 98 starts, it sends an announcement to the browser service to inform the browser of its availability. Figure I.3 shows browser announcements being transmitted.
Figure I.3 Browser Announcements
Master browsers are responsible for receiving announcements from and returning lists of backup browsers to computers running any of the following operating systems:
Windows NT 3.1
Windows NT Advanced Server 3.1
Windows for Workgroups
Windows NT Workstation 3.5, or later
Windows NT Server 3.5, or later
Windows 2000 Professional
Windows 2000 Server
When a computer starts and the value of the MaintainServerList entry in its registry is set to Auto , the master browser is responsible for telling the system whether or not to become a backup browser.
When a computer becomes the master browser by winning an election, and the browse list is empty, the master browser forces all systems to reply with an announcement. The master browser broadcasts a datagram called a RequestAnnouncement. All computers that receive this datagram must answer after a random delay of up to 30 seconds. This 30-second range for response prevents the master browser from becoming overloaded and losing replies, and it protects the network from being flooded with responses. Figure I.4 shows computers browsing for backup lists.
Figure I.4 Browsing for Backup Lists
A master browser cannot be forced to rebuild the browse list for a workgroup or domain. However, shutting down and restarting a computer that is configured as the preferred master browser, or stopping and restarting the browser service, forces the building of a new browse list. When a preferred master browser starts, it forces an election, which it wins. Because there is no browse list, it then forces all members of the domain or workgroup to announce themselves.
If a master browser receives an announcement from another computer that claims to be the master browser, the master browser will demote itself from master browser and force an election. This ensures that there is never more than one master browser in each workgroup or domain.