Domains

An aspect of addresses common to many communications networks is the concept of domains. Domains put the data processing resources in a network under a common control.

For example, the structure of the Internet illustrates how domains define the Internet Protocol (IP) address. The Internet is an extensive network made up of many different smaller networks. To facilitate routing and addressing, Internet addresses are hierarchically structured in domains, with very broad categories at the top such as com for commercial users, edu for educational users, and gov for government users.

Within the com domain are many smaller domains corresponding to individual businesses; for example, ibm. Within the ibm.com domain are even smaller domains corresponding to the Internet addresses for various locations, such as austin.ibm.com or raleigh.ibm.com. At this level, we start seeing names of hosts. A host, in this context, is any computer connected to the network. Within austin.ibm.com, there may be hosts with the names hamlet and lear, which are addressed hamlet.austin.ibm.com and lear.austin.ibm.com.