4.2. The Domain Name System
So far we have seen how an individual host is identified by its IP address. This numerical address is perfectly suited for processing by routers or computers, but it is rather user unfriendly. Therefore, it is desirable that, in addition to the IP address, hosts should have symbolic names. For example, AT&T's Web server is known to most users as www.att.com and not as 192.20.3.54. The mapping between the symbolic name and the numerical IP address used to address IP packets is performed by the Domain Name System (DNS).
4.2.1. Name Hierarchy
To decentralize both the management of host names and their translation into IP addresses, DNS organizes host names into hierarchical domains. Each domain is given a name, which ...
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