DNS is a crucial element of both Internet and Active Directory communications. All TCP/IP communication is based on IP addresses. Each computer on a network has at least one network interface, which is called a host in TCP/IP parlance, and each host has an IP address that is unique on that network. Every datagram transmitted by a TCP/IP system contains the IP address0 of the sending computer and the IP address of the intended recipient. However, when users access a shared folder on the network or a website on the Internet, they usually do so by specifying or selecting a host name, not an IP address. This is because names are far easier to remember and use than IP addresses.
Following are points which will discuss in coming sections