DNS (Domain Name System) is utilized on the Internet too on many private networks. Networks employing Microsoft Active Directory service employ DNS to decide computer names and to place computers within their local networks and the Internet. Networks derived from Windows 2000 Server and Windows Server 2003 use DNS as a primary denotes of locating resources in Active Directory.

The domain namespace is the naming scheme that proposed the hierarchical structure for the DNS database. Every node, referred to as a domain, represents a partition of the DNS database. The DNS database is indexed by name, so each domain should have a name. As you attach domains to the hierarchy, the name of the parent domain is extra to its child domain (sub domain). A domain’s name recognizes its place in the hierarchy.

At the top of the DNS hierarchy, there is a single domain called the root domain, which is symbolized by a single period (.).

Top level domains are grouped by association type or geographic location. Top level domains are handled by the Internet Architecture Board (IAB), an Internet authority scheming the task of domain names, among other belongings. Examples are .com, .gov and .net

Anybody can register a second level domain name. Second level domain names are registered to persons and organizations by a number of dissimilar domain registry companies. A second level name has two name parts: a top level name and a sole second level name such as Microsoft site.

A DNS name server stores the zone database file. Name servers can store data for one zone or multiple zones. A name server is said to have power for the domain name space that the zone includes. One name server holds the master zone database file, referred to as the primary zone database file, for the particular zone. As a result, there must be at least one name server for a zone. Alters to a zone, such as adding domains or hosts, are performed on the server that encloses the primary zone database file.

Name resolution is the procedure of resolving names to IP addresses. It is similar to looking up a name in a telephone book, in which the name is associated with a telephone number. For example, when you connect to the Microsoft Web site, you use the name Microsoft site. DNS resolves Microsoft site to its linked IP address. The mapping of names to IP addresses is stored in the DNS dispersed database. DNS name servers decide forward and reverse lookup queries. A forward search for query resolves a name to an IP address, and a reverse search for query resolves an IP address to a name. A name server can decide a query only for a zone for which it has power. If a name server cannot resolve the query, it passes the inquiry to other name servers that can decide it. The name server caches the inquiry results to decrease the DNS traffic on the network.

1. The client passes a forward search for query for Microsoft site to its local name server.

2. The local name server ensures its zone database file to decide whether it contains the name-to-IP address mapping for the client query. The local name server does not have authority for the Microsoft site domain, so it passes the query to one of the DNS root servers, requesting resolution of the host name. The root name server sends back a referral to the com name server.

3. The local name server sends a demand to a com name server, which reacts with a transfer to the Microsoft name server.

4. The local name server sends a request to the Microsoft name server. Because the
Microsoft name server has power for that portion of the domain namespace, when it receives the request, it returns the IP address for Microsoft site to the local name server.

5. The local name server sends the IP address for Microsoft site to the client.

6. The name resolution is total and the client can access Microsoft site.