Windows Internet Naming Service (WINS) enables computers to register and resolve NetBIOS names. WINS is maintained primarily for backward support and compatibility with early versions of Microsoft Windows, including Windows 95, Windows 98, and Windows NT, that used WINS for computer name resolution; or for networks running Windows 2000 or later that don't have Active Directory directory service deployed and thus don't require DNS. On most large networks, WINS is needed to support Windows 95, Windows 98, and Windows NT computers.
If you are setting up a new network, you probably don't need WINS. On an existing network running all Microsoft Windows 2000, Windows XP, and Windows Server 2003 systems, only the Domain Name System (DNS) is needed because these computers rely exclusively on DNS for name resolution if Active Directory is deployed. Because WINS is not required, WINS support could be removed from the network. Doing so, however, would mean that applications and services that rely on NetBIOS, such as the computer Browser service, would no longer function.
Like DNS, WINS is a client/server protocol. All Windows servers have a WINS service that can be installed to provide WINS services on the network. All Windows computers have a WINS client that is installed automatically. The Workstation and Server services on computers are used to specify resources that are available, such as file shares. These resources have NetBIOS names as well.
WINS architecture is very different from DNS. Unlike DNS, WINS has a flat namespace and doesn't use a hierarchy or tree. Each computer or resource on a Windows network has a NetBIOS name, which can be up to 15 characters long. This name must be unique on the network—no other computer or resource can have the same name. Although there are no extensions to this name per se that indicate a domain, a NetBIOS scope can be set in Dynamic Host Configuration Protocol (DHCP).
The NetBIOS scope is a hidden 16th character (suffix) for the NetBIOS name. It is used to limit the scope of communications for WINS clients. Only WINS clients with the same NetBIOS scope can communicate with each other. See the section entitled "Configuring TCP/IP Options" for details on setting the NetBIOS scope for computers that use DHCP.
The ways WINS works on a network is determined by the node type set for a client. The node type defines how name services work. WINS clients can be one of four node types:
B-Node (Broadcast Node) Broadcast messages are used to register and resolve names. Computers that need to resolve a name broadcast a message to every host on the local network, requesting the IP address for a computer name. Best for small networks.
P-Node (Peer-to-Peer Node) WINS servers are used to register and resolve computer names to Internet Protocol (IP) addresses. Computers that need to resolve a name send a query message to the server and the server responds. Best if you want to eliminate broadcasts. In some cases, however, resources might not be seen as available if the WINS server isn't updated by the computer providing the resources.
M-Node (Mixed Node) A combination of B-Node and P-Node. WINS clients first try to use broadcasts for name resolution. If this fails, the clients then try using a WINS server. Still means a lot of broadcast traffic.
H-Node (Hybrid Node) A combination of B-Node and P-Node. WINS clients first try to use a WINS server for name resolution. If this fails, the clients then try broadcasts for name resolution. Best for most networks that use WINS servers because it reduces broadcast traffic.
WINS maintains a database of name-to-IP-address mappings automatically. Whenever a computer or resource becomes available, it registers itself with the WINS server to tell the server the name and IP address it is using. As long as no other computer or resource on the network is using that name, the WINS server accepts the request and registers the computer or resource in its database.
Name registration isn't permanent. Each name that is registered has a lease period associated with it, which is called its Time to Live (TTL). A WINS client must reregister its name before the lease expires and attempts to do so when 50 percent of the lease period has elapsed or when it is restarted. If a WINS client doesn't reregister its name, the lease expires and is marked for deletion from the WINS database. During normal shutdown, a WINS client will send a message to the WINS server requesting release of the registration. The WINS server then marks the record for deletion. Whenever records are marked for deletion, they are said to be tombstoned.
As with DNS clients, WINS clients maintain a cache of NetBIOS names that have been looked up. WINS cache, however, is designed to hold only names looked up recently. By default, names are cached for up to 10 minutes and the cache is limited to 16 names. You can view entries in the NetBIOS cache by typing nbtstat-c at the command prompt.
On most networks that use WINS, you'll want to configure at least two WINS servers for name resolution. When there are multiple WINS servers, you can configure replication of database entries between the servers. Replication allows for fault tolerance and load balancing by ensuring that entries in one server's database are replicated to its replication partners. These replication partners can then handle renewal and release requests from clients as if they held the primary registration in the first place.
For Windows Server 2003, WINS has several important updates, including the following:
Persistent connections In a standard configuration, replication partners establish and release connections each time they replicate WINS database changes. With persistent connections, replication partners can be configured to maintain a persistent connection. This reduces the overhead associated with opening and closing connections and speeds up the replication process.
Automatic replication partners Using automatic replication partners, WINS can automatically configure itself for replication with other WINS servers. To do this, WINS sends periodic multicast messages to announce its availability. These messages are addressed to the WINS multicast group address (224.0.1.24), and any other WINS servers on the network that are listening for datagrams sent on this group address can receive and process the automatic replication request. Once replication is set up with multicast partners, the partners use standard replication with either persistent or nonpersistent connections.
Manual tombstoning Manual tombstoning allows administrators to mark records for deletion. A record marked for deletion is said to be tombstoned. This state is then replicated to a WINS server's replication partners, which prevents the record from being re-created on a replication partner and then being replicated back to the original server on which it was marked for deletion.
Record export The record export feature allows administrators to export the entries in the WINS database to a file that can be used for tracking or reporting on which clients are using WINS.