Why we need Domain Name System

Human can identified using birth certificate name, National Identity card numbers, driving license numbers. But my entire friend identified me with my birth certificate name because more mnemonic birth certificate names rather than National Identity card number.

indeed, can you imagine saying,

 Just as humans can be identified in many ways, so too can Internet hosts. One identifier for a host is its hostname. Hostnames—such as www.google.lk, www.yahoo.com, gaia.cs.umass.edu, and cis.poly.edu—are mnemonic. However, hostnames provide little, if any, information about the location within the Internet of the host. (A hostname such as www.dialog.lk, which ends with the country code .lk, tells us that the host is probably in Sri Lanka, but doesn’t say much more.) Furthermore, because hostnames can consist of variable length alphanumeric characters, they would be difficult to process by routers. For these reasons, hosts are also identified by so-called IP addresses.

An IP address is hierarchical because as we scan the address from left to right, we obtain more and more specific information about where the host is located in the Internet (that is, within which network, in the network of networks). Similarly, when we scan a postal address from bottom to top, we obtain more and more specific information about where the addressee is located.

We have just seen that there are two ways to identify a host—by a hostname (www.dialog.lk) and by an IP address(123.234.65.79). People prefer the more mnemonic hostname identifier, while routers prefer fixed-length, hierarchically structured IP addresses. In order to reconcile these preferences, we need a directory service that translates hostnames to IP addresses. This is the main task of the Internet’s domain name system (DNS).