WINS servers

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2, Windows Server 2008, Windows Server 2008 R2, Windows Server 8 Beta

WINS servers

WINS consists of two main components, the WINS server and WINS clients.

The WINS server handles name registration requests from WINS clients, register their names and IP addresses, and responds to NetBIOS name queries submitted by clients, returning the IP address of a queried name if it is listed in the server database.

Also, as the following graphic shows, WINS servers can replicate the contents of their databases (which contain NetBIOS computer name mappings to IP addresses) to other WINS servers. When a WINS-enabled client computer (such as a workstation computer on either Subnet 1 or Subnet 2) starts on the network, its computer name and IP address are sent in a registration request directly to its configured primary WINS server, WINS-A. Because WINS-A is the server that registers these clients, it is said to be the owner for the records of the clients in WINS.

WINS servers

In this example, server WINS-A has clients registering with it that are both local (that is, clients on Subnet 2 where it resides) and remote (clients located across a router on Subnet 1). A second WINS server, WINS-B, is located on Subnet 3 and only owns mappings for local clients registering from its same subnet. WINS-A and WINS-B can later complete replication of their databases so that records for clients on all three subnets are in the WINS database at both servers. For more information, see WINS Replication.

Primary/Secondary WINS servers

WINS servers are used by clients in one of two ways: either as a primary or secondary WINS server.

The difference between primary and secondary WINS servers is not based in any way on the servers (that for all functional purposes are the same in WINS). The difference occurs at the client which differentiates and orders the list of WINS servers when provided more than one WINS server to use.

For most cases, the client contacts the primary WINS server for all of its NetBIOS name service functions (name registration, name renewal, name release, and name query and resolution). The only case where secondary WINS servers are ever used is when the primary WINS server is either:

  1. Unavailable on the network when the service request is made, or

  2. Unable to resolve a name for the client (in the case of a name query).

In the case of a failure by the primary WINS server, the client requests the same service function from its secondary WINS servers. If more than two WINS servers are configured at the client, the additional WINS servers are tried until the list is exhausted or one of the secondary WINS server succeeds in processing and responding to the request. After a secondary WINS server is used, a client periodically tries to switch back to its primary WINS server for future service requests.

For most recent WINS clients (Windows XP and Windows 2000), a list of up to 12 secondary WINS servers can be configured (either manually through TCP/IP properties or dynamically by a DHCP server providing a list using DHCP option type 44). This feature is useful in an environment where there is a large number of mobile clients and NetBIOS-based resources, and services are used often. Because in these types of environments, the WINS database may not be consistent throughout the network of WINS servers because of convergence issues, it can be helpful for clients to be able to query more than two WINS servers.

However, this option should not be overused needlessly as it produces a tradeoff in terms of the actual benefit for adding fault tolerance by listing additional WINS servers. The benefit of this feature must be weighed against the fact that for each additional WINS server listed, the time to process a query request fully in WINS takes incrementally longer to achieve. For example, if a WINS client tries three or more WINS servers before failing, it can substantially delay the processing of the name query before alternative methods for resolution are tried, such as searching of a local Hosts file or querying a DNS server.