Domain Name System ( DNS )

Domain Name System (DNS) is one of the industry-standard suite of protocols that comprise TCP/IP. Windows Server DNS is implemented using two software components: the DNS server and the DNS client (or resolver). Both components are run as background service applications.

By default, Windows Server DNS is used for all name resolution in a Windows Server network. In the most typical scenario, when a Windows Server network user specifies the name of a network host or an internet DNS domain name, the DNS Client service running on the Windows Server computer of the user contacts a DNS server to resolve the name to an IP address. 

DNS in TCP/IP 

 

Technologies that use DNS

DNS and AD DS

Active Directory Domain Services (AD DS) uses DNS as its domain controller location mechanism. When any of the principal Active Directory operations is performed, such as authentication, updating, or searching, computers running Windows Server 2008 use DNS to locate Active Directory domain controllers and these domain controllers use DNS to locate each other. 

DNS and WINS

The earlier method of name resolution for a Windows network was Windows Internet Name Service (WINS). DNS is different from WINS in that DNS is a hierarchical namespace and WINS is a flat namespace. Clients and applications that rely on NetBIOS names continue to use WINS for name resolution. Because Windows Server 2008 DNS is WINS-aware, a combination of both DNS and WINS can be used in a mixed environment to achieve maximum efficiency in locating various network services and resources.

DNS and DHCP

The DHCP service provides default support to register and update information for legacy DHCP clients in DNS zones. Legacy clients typically include other Microsoft TCP/IP client computers that were released prior to Windows 2000. The Windows Server 2008 DNS-DHCP integration enables a DHCP client that is unable to dynamically update DNS resource records directly to have this information updated in DNS forward and reverse lookup zones by the DHCP server.

How DNS Works

Domain Name System (DNS) is the default name resolution service used in a Windows Server network. Previously, we have Windows Internet Name Service (WINS) in Windows NT for the same purpose. A DNS Client resolver is included as a default service in all client and server versions of the Windows operating system. 

Typically, Windows Server 2008 DNS is deployed in support of Active Directory Domain Services (AD DS). In this environment, DNS namespaces mirror the Active Directory forests and domains used by an organization. Network hosts and services are configured with DNS names so that they can be located in the network, and they are also configured with DNS servers that resolve the names of Active Directory domain controllers. 

DNS architecture is a hierarchical distributed database and an associated set of protocols that define:

• A mechanism for querying and updating the database.
• A mechanism for replicating the information in the database among servers.
• A schema of the database.

DNS originated in the early days of the Internet when the Internet was a small network established by the United States Department of Defense for research purposes.

The Domain Name System introduced in 1984 became this new system. DNS supports hierarchical names and allows registration of various data types in addition to host name-to-IP address mapping used in HOSTS files.

The original DNS was based on Request for Comment (RFC) 882 (Domain Names: Concepts and Facilities) and RFC 883 (Domain Names–Implementation and Specification), which were superseded by RFC 1034 (Domain Names–Concepts and Facilities), and RFC 1035 (Domain Names–Implementation and Specification). Additional RFCs that describe DNS security, implementation, and administrative issues later augmented the original design specifications. 

DNS domain names

The Domain Name System is implemented as a hierarchical and distributed database containing various types of data, including host names and domain names. The names in a DNS database form a hierarchical tree structure called the domain namespace. Domain names consist of individual labels separated by dots, for example: mydomain.microsoft.com.

A fully qualified domain name (FQDN) uniquely identifies the host’s position within the DNS hierarchical tree by specifying a list of names separated by dots in the path from the referenced host to the root. The following figure shows an example of a DNS tree with a host called mydomain within the microsoft.com. domain. The FQDN for the host would be mydomain.microsoft.com.