The Windows Internet Naming Service (WINS) provides NetBIOS name resolution for clients on a network. NetBIOS names are used by legacy clients such as Windows NT 4.0 and Windows 95. A WINS server stores a database containing NetBIOS name to IP address mappings. A Windows Server 2003 machine can be configured as a WINS Server. Even though a native Windows 2003 environment can do without WINS, WINS may still be required by some legacy applications. Most modern networks contain a broad range of clients and applications, therefore WINS remains an important service. WINS servers can also share their databases with other WINS servers (Replication). This allows clients on remote subnets to communicate using NetBIOS names.
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WINS Name Resolution
Every Microsoft computer is configured to use one of the 4 different node types. A Node Type tells the computer how to resolve a name. Microsoft recommends that you configure a computer to use H-Node resolution.
- Broadcast (B-Node).
- Peer (P-Node).
- Mixed (M-Node).
- Hybrid (H-Node).
Broadcast (B-node) – B-node uses only a broadcast to resolve NetBIOS names. Clients configured with B-node will never use WINS. B-node is often used when there are no name servers available.
Peer (P-node) – P-node uses WINS only. It will never use a broadcast, even if the WINS server cannot resolve the name. It is used to reduce traffic in large networks.
Mixed (M-node) – M-node uses a combination of broadcast and WINS. Clients configured to use M-node first use a broadcast (B-node) to resolve; if that is unsuccessful, they query the configured WINS server (P-node).
Hybrid (H-node) – H-node uses a combination of broadcast and WINS. Clients configured to use H-node first query the WINS server (P-node); if that is unsuccessful, they try broadcast (B-node) to resolve.
When a H-node client configured to use WINS needs to resolve a hostname, it goes through the following stages:
- Client checks its NetBIOS name cache.
- Client queries the WINS server.
- Client sends a broadcast.
- Client checks its LMHOSTS file.
- Client checks its HOSTS files.
- Client queries a DNS Server.
To find out which node type a client is using. Use the ipconfig /all command from a command prompt.
When a Windows client computer enters the network, it registers its name with a WINS Server so that other client machines can resolve its name to an IP address. By default a client is allowed its name for six days before it needs to renew it. This allows the name to be freed up when not in use.
When a client is shut down, its name is marked as released. The name still belongs to the client but the name is not in use. By default, the name is marked as extinct for four days before being removed. In a very dynamic environment with computers frequently entering and exiting the network, the renewal interval and extinction level can be lowered.