How Browsing a Wide Area Network Works

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1
• Microsoft Windows NT Workstation versions 3.5, 3.51, and 4.0
• Microsoft Windows NT Server versions 3.5, 3.51, and 4.0

SUMMARY

This article explains how browsing over a wide area network (WAN) works in a domain and a workgroup.

MORE INFORMATION

The Primary Domain Controller (PDC) of a WAN domain that spans subnets acts as a domain master browser server. Each subnet in that domain has its own master browser server, which sends master browser announcement requests to the domain master browser.

On receipt of a request from a server, the domain master browser replies with a remote NetServerEnum API, collects the servers from that master, then merges that list with its current list. This guarantees that the domain master browser server maintains a complete list of domain servers. When a client remotely sends a NetServerEnum API to the domain master browser server, the domain master returns to all servers in its browse list.

WAN browsing support is available only in a domain environment among Windows NT and Windows NT Advanced Server machines. If a domain contains at least one Windows NT Advanced Server machine, you can browse that domain. A subnet that has only Windows NT workstations running Browser services can browse the entire contents of that domain.

To guarantee that the master browser for each subnet can access the PDC, a domain's PDC must be listed in each client's LMHOSTS file. To guarantee that the PDC can request the local subnet's list from the subnet master browser, the TCP/IP transport must cache client addresses for some amount of time. In addition, lists of domains retrieved by the master browser have only the domains that are occupied by other master browser servers in that domain.

Windows NT or WFW workgroups cannot span multiple subnets. Workgroups can view only other workgroups on the local subnet.

Here are some conditions under which browsing does not work:

1. Computers in a remote subnet cannot be seen by clients in a Windows NT or WFW workgroup. However, if there is a Windows NT on the workgroup, the workgroup administrator can configure one or more of the Windows NT workstations as "Configured Master Browsers," then add those computers in the remote subnet to the LMHOSTS file.

2. You cannot browse remote subnets with only WFW clients, because the WFW browser is not WAN-aware.

3. When browsing, you cannot see an isolated workgroup or a domain that is on a subnet with no machines in the current domain.

   For example: Suppose domain A spans 3 subnets(S1,S2 and S3). PDC for domain A is on S1. S2 has a BDC for domain A. S3 has an NT machine that is a part of domain A. S3 also has a few machines that belong to domain B, the PDC for which is elsewhere.

   Now, when the browse master of S3 (NT wksta) sends the list of servers in its local subnet to the PDC of domain A, it also sends a list of domains in its subnet that includes domain B. So PDC of domain A has a list of domains that has domain B listed in it. When browse master of S2 gets the browse list from PDC, it gets the list of domains as well, and that includes domain B. So it knows the existence of domain B. But for a client (on S2) to get the list of servers in domain B, it sends a request to its browse master on S2 and S2 in turn contacts the browse master of domain B on S3. For the browse master of S2 to contact the browse master of S3, its IP address has to be listed in its LMHOSTS file.

   Now, if S3 does not have any machines in its subnet that belong to domain A, then S1 and S2 cannot browse domain B.

4. You cannot browse domains on other subnets where the browse masters are not listed in the LMHOSTS file.