Some of the main topics in this chapter are
A Master Browser keeps track of every network member. Every Windows NT domain has one. The Master Browser prevents each machine on the network from having to broadcast its presence to be visible. The result is better performance.
Windows NT provides for backup browsers, too, which maintain the same list of members in case the Master Browser goes down. On most networks, the Master Browser is on the PDC. If the PDC goes down (which happens from time to time), the backup browser becomes the new Master Browser, taking over where the previous Master Browser left off.
Each time an NT Server starts, it initiates an election. This is the process by which the network determines the computer that's best suited to act as the Master Browser. In most cases, the PDC is always the Master Browser, but if a PDC isn't available on the network, any other computer on the network can fill this role. Think of this process like the child's game King of the Hill. Each time a new server goes online, it challenges the other computers on the network for the Master Browser role. If the new server is best suited to fill this role, it bumps off the current Master Browser.
Computers on the network don't actually vote for a Master Browser. Each computer reports its potential to act as a Master Browser; then, the computer with the highest potential becomes the Master Browser. The computer with the most "toys" wins. The one exception to this is when different versions of networking software are in use; in this case, the computer running the latest software automatically becomes the Master Browser.
In addition to bringing a new Server online, there are other times when elections occur:
You can better understand how elections occur by looking at the step-by-step procedure an NT network uses:
2. If the new server's browser version is higher than the existing Master Browser, the new server becomes the current Master Browser. If the new server's browser version is lower than the current Master Browser, the Master Browser might elect to assign the new server as a backup browser.
NOTE: On an NT network, there's one backup browser for every 32 nodes on a segment. The Master Browser is solely responsible for picking the backup browsers from the list of best-suited computers.
4. The winning browser, now the Master Browser, starts the election process up to four more times to make sure no new servers have started, missing the first elections. This process enables a large number of servers to come online at one time.
TIP: NT records browser elections in the system event log, which you can inspect by using the Event Viewer.
In Step 3 in the previous section, you learn that two computers might have to compete for the role of Master Browser. In general, the following list shows you the priority by which this decision is made:
2. Stand-alone NT Server
3. Windows NT Workstation
4. Windows 95
5. Windows for Workgroups
If the preceding criteria don't resolve the issue, a finer set of criteria is applied. In the following list, you see that a server configured as a preferred Master Browser wins over a server that's not configured as a preferred Master Browser, even though the latter might be the current Master Browser:
2. Configured as a preferred Master Browser
3. Currently a Master Browser
4. MaintainServerList is yes (see HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Browser\Parameters in the NT Registry).
5. Currently a backup browser
TIP: You can force a particular NT computer to always be the Master Browser by setting the REG_SZ value entry called IsDomainMasterBrowser to "True" in HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Browser\Parameters.
When a computer that is not a browser candidate first starts, it sends a server announcement to the Master Browser. As a result, the Master Browser adds the computer to the browse list. The Master Browser can optionally assign one of these computers the backup browser role, as you learned earlier.
At first, a computer sends a server announcement to the Master Browser once every minute or so. The longer the computer remains online, however, the bigger the interval between server announcements becomes. Thus, a computer that's been online for quite a while sends server announcements at an interval of about 12 minutes. If, after a few intervals, the Master Browser has not heard from a computer on the browse list, it removes the computer.
When a new Master Browser is elected, as described in Step 4 of the "Elections Step- by-Step" section, it sends a request announcement to all computers on the network. This request must be honored and demands that each computer re-register with the Master Browser. Each computer registers at random intervals to prevent flooding the Master Browser.
A Master Browser and backup browser exist on each subnet of a multi-segmented network. A multi-segmented network is one on which a router routes traffic from one network segment to another; each segment has a different subnet address. Each side of a dial-up networking connection works like an individual segment, too.
For a user to browse the network across segments, some method must exist to combine the browse lists for each segment into a single list. The PDC for a multi-segmented domain fulfills that role. It serves as the domain Master Browser. A domain Master Browser combines the browse lists for each segment and communicates the combined list back to each segment's Master Browser.
Here's how the process works:
2. The domain Master Browser builds a list of all the computers on each network segment. The domain Master Browser updates this list every 15 minutes.
3. The domain Master Browser merges each list.
4. The Master Browser on each subnet requests the merged list from the domain Master Browser. It does so every 15 minutes.
The primary means by which a Windows 95 or Windows NT user browses the network is the Network Neighborhood (see Figure 17.1). The user can see a list of the servers available and browse the resources on those servers.
The Network Neighborhood effectively makes network resources appear as a simple extension of the user's computer.
Each client builds that list in the following manner:
2. Each time the client needs a browse list, it randomly selects a backup browser. The random selection prevents overloading any one machine.
3. If the browser can't connect to one of the backup browsers, it relies on the Master Browser. If it can't contact the Master Browser, the client posts a force election to force a browser election.
Bad timing causes problems. A Master Browser might not remove an unavailable computer from the browse list for up to 36 minutes, considering that with long intervals a machine announces itself every 12 minutes and a Master Browser gives a machine three intervals before removing it from the list. You have noticed that sometimes a machine that is definitely on the network isn't available in Network Neighborhood. This is because bad timing prevented the backup browsers from receiving the latest information from the Master Browser. Note that backup browsers get a new copy of the browse list every 15 minutes.
TIP: If you're sure that a computer is available on the network, but it doesn't appear in Network Neighborhood, you can use the Start button to browse it anyway. Choose Run, type the UNC path of the network computer, and press Enter. For example, type \\Server and press Enter to open Server in a folder.
You can manually add domains to a server's browse list:
2. Select the Computer Browser service, and click Configure.
3. Type the name of the domain you want to add to the browse list, and click Add.
4. Close the Browser Configuration dialog box and the Network Properties dialog box.
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