Name Resolution Technologies
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Name Resolution Technologies
Microsoft Windows Server 2003 operating systems use name resolution to translate the numerical IP addresses that are used for TCP/IP communications to computer names, which are easier for users to remember. With name resolution, computer names are assigned to the IP addresses of the source and destination hosts, and are then used to contact these hosts, rather than using the 32-bit IP addresses.
In Windows Server 2003, there are two types of TCP/IP names to resolve:
Host names
NetBIOS names
Name Resolution Components
Windows Server 2003 provides Domain Name System (DNS) for host name resolution and Windows Internet Name Service (WINS) for NetBIOS name resolution.
DNS Name Resolution
DNS name resolution means successfully mapping a DNS domain or host name to an IP address. A host name is an alias that is assigned to an IP node to identify it as a TCP/IP host. The host name can be up to 255 characters long and can contain alphabetic and numeric characters, hyphens, and periods. Multiple host names can be assigned to the same host.
Windows Sockets (Winsock) programs, such as Internet Explorer and the FTP utility, can use one of two values for the destination host: the IP address or a host name. When the IP address is specified, DNS name resolution is not needed. When a host name is specified, the host name must be resolved to an IP address before IP-based communication with the desired resource can begin.
Host names can take various forms. The two most common forms are a nickname and a domain name. A nickname is an alias to an IP address that individuals can assign and use. A domain name is a structured name in a hierarchical namespace called DNS. An example of a domain name is www.microsoft.com.
Nicknames are resolved through entries in the Hosts file, which is stored in the systemroot\System32\Drivers\Etc folder. For more information, see TCP/IP Technical Reference.
Domain names are resolved by sending DNS name queries to a DNS server. The DNS server is a computer that stores domain name-to-IP address mapping records or has knowledge of other DNS servers. The DNS server resolves the queried domain name to an IP address and returns the name-to-IP address mapping records in response to a query.
Windows Server 2003 client computers must be configured with the IP address of a DNS server in order to resolve domain names. Active Directory-based computers running Microsoft Windows XP Professional or Windows Server 2003 operating systems must be configured with the IP address of a DNS server. For more information, see DNS Technical Reference.
WINS Name Resolution
WINS name resolution means successfully mapping a NetBIOS name to an IP address. A NetBIOS name is a 16-byte address that is used to identify a NetBIOS resource on the network. A NetBIOS name is either a unique (exclusive) or group (nonexclusive) name. When a NetBIOS process is communicating with a specific process on a specific computer, a unique name is used. When a NetBIOS process is communicating with multiple processes on multiple computers, a group name is used.
The exact mechanism by which NetBIOS names are resolved to IP addresses depends on the NetBIOS node type that is configured for the node. RFC 1001, “Protocol Standard for a NetBIOS Service on a TCP/UDP Transport: Concepts and Methods,” defines the NetBIOS node types, as listed in the following table.
NetBIOS Node Types
| Node Type | Description |
|---|---|
B-node(broadcast) |
B-node uses broadcast NetBIOS name queries for name registration and resolution. B-node has two major limitations: (1) Broadcasts disturb every node on the network, and (2) Routers typically do not forward broadcasts, so only NetBIOS names on the local network can be resolved. |
P-node (peer-peer) |
P-node uses a NetBIOS name server (NBNS), such as a WINS server, to resolve NetBIOS names. P-node does not use broadcasts; instead, it queries the name server directly. |
M-node (mixed) |
M-node is a combination of B-node and P-node. By default, an M-node functions as a B-node. If an M-node is unable to resolve a name by broadcast, it queries a NBNS using P-node. |
H-node(hybrid) |
H-node is a combination of P-node and B-node. By default, an H-node functions as a P-node. If an H-node is unable to resolve a name through the NBNS, it uses a B-node to resolve the name. |
Computers running Windows Server 2003 operating systems are B-node by default and become H-node when they are configured with a WINS server. Those computers can also use a local database file called Lmhosts to resolve remote NetBIOS names. The Lmhosts file is stored in the systemroot\System32\Drivers\Etc folder. For more information, see TCP/IP Technical Reference.
Typically, Windows-based computers are configured with the IP address of a WINS server so remote NetBIOS names can be resolved. Active Directory-based computers, such as Windows XP Professional, Microsoft Windows 2000 and Windows Server 2003 operating systems, must be configured with the IP address of a WINS server if they are to communicate with computers running Microsoft Windows NT, Windows 95, Windows 98, or Windows Millennium Edition that are not Active Directory-based. For more information about WINS, see WINS Technical Reference.
Name Resolution Scenarios
DNS is the name resolution service of Windows 2000, Windows XP, and Windows Server 2003. Windows clients use DNS for name resolution and service location, including locating Active Directory domain controllers for logon. Pre-Active Directory clients (Windows NT 3.5 and 3.51, Windows NT 4.0, Windows 95, and Windows 98), however, rely on NetBIOS, which can use WINS, broadcast, or flat Lmhosts file. In particular, WINS is used by Pre-Active Directory clients for domain controller location. Windows NT 4.0-based clients can register themselves in Windows Server 2003 WINS. Clients running Windows 2000, Windows XP, and Windows Server 2003 can register in Windows NT 4.0 WINS.
The DNS implementation in Windows 2000, Windows XP, and Windows Server 2003 is WINS-aware, and, as a result, a combination of both DNS and WINS is typically used to achieve maximum efficiency in locating various network resources in a mixed environment.