Resolving Names Through a WINS Server for Non-WINS Clients

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Resolving Names Through a WINS Server for Non-WINS Clients

You can also allow non-WINS clients to use a WINS server to resolve NetBIOS names by installing a WINS proxy agent. By definition, a non-WINS client cannot directly communicate with a WINS server to resolve a name. The non-WINS client resolves names by resorting to a b-node broadcast. If you install a WINS proxy agent, the proxy agent forwards any broadcasts for name resolution onto the WINS server. The proxy agent must be located on the same subnet as non-WINS clients so the proxy agent receives the broadcast for name resolution.

When a non-WINS client broadcasts a name resolution request, a proxy agent that hears the broadcast checks its own NetBIOS name cache to see whether an entry exists for the requested name. If the entry doesn’t exist, the proxy agent adds to the cache an entry for that name with the status of pending. The proxy agent then sends a name resolution request for the same name to the WINS server. After the WINS server responds with the name resolution, the proxy agent adds the entry to its cache and then removes the pending status from the entry.

The proxy agent does not forward the response to the non-WINS client making the request. When the non-WINS client broadcasts another request for the name resolution, the proxy agent now finds an entry for the name in its cache and the proxy agent can respond to the non-WINS client with a successful name resolution response.

The WINS proxy agent also forwards registration requests to the WINS server. However, registration requests for non-WINS clients are not added to the WINS server’s database. The WINS server uses these forwarded registration requests to see whether there are any potential conflicts in its database with the requested name registration. You must still add static entries to the WINS database so names of non-WINS clients can be resolved.

You must place a WINS proxy agent on each subnet where non-WINS clients are located so those clients have access to the WINS server. Because those clients resolve names only by using broadcasts, which are not typically routed, those broadcasts never go beyond the subnet. With a proxy agent on each subnet, broadcasts on each subnet can then be forwarded to the WINS server. You can have two proxy agents on a subnet, but you shouldn’t exceed this limit. Even having more than one proxy agent on a subnet can generate excessive work for the WINS server because each proxy agent forwards name resolution and name registration requests to the WINS server. The WINS server has to respond to duplicate messages from proxy agents if more than one proxy agent is on a subnet.

Any Windows-based WINS client can be a WINS proxy agent. To configure an NT server or workstation to be a proxy agent, you must turn on a parameter in the registry. This proxy agent cannot be a WINS server. Windows 95 and Windows for Workgroups computers are more easily configured by turning on a switch in the TCP/IP configuration. Exercise 9.13 at the end of the chapter shows how to configure a Windows NT computer and a Windows 95 computer to be a WINS proxy agent.

To make an NT server or workstation into a proxy agent, open
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\NetBT \Parameters
and change the value of the EnableProxy parameter to 1.

After you configure a WINS client to be a proxy agent, you must reboot the machine for this change to take effect. No other configuration is needed for this proxy agent. This WINS client remains a proxy agent until you turn off the proxy agent parameter and reboot the computer.

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