Domains and Hosts
Domains and Hosts on the Internet
Network connections on the Internet have names and addresses that obey certain conventions. For computers, the names conform to the conventions of the Domain Name System, which maps an Internet Address to the more easily remembered host and domain name. The Internet Protocol (or IP) Address is a set of numbers that expresses the exact connection between a computer and the network on the Internet. It is easier to understand Domain naming, however, if you look at an IP address first. IP addresses have four sets of numbers (octets) separated by periods or dots. These combined parts are unique on the network and allow the network to know specifically which computer is to receive which electronic packet as well as specifically from which computer the electronic packet came. The computer is known as a host, and the IP address, its network connection, is known as the host address. The IP address is difficult to remember, is easy to mis-enter, and will not necessarily remain the same if someone needs to reorganize their network. The recognition of the difficulty with these addresses brought the Domain Name System (DNS), which maps IP addresses to a set of names.

Nongeographic Domains

There are six (6) common domain types that are nongeographical:

  • com - for commercial organizations, e.g.,,, etc
  • net - for network organizations, e.g.
  • gov - for United States government, e.g.,,, etc.
  • edu - for accredited 4-year colleges and universities, e.g.,,,, etc.
  • mil - for the military, non-classified networks, e.g,, etc.
  • org - organizations that do not otherwise fit into the other designations, e.g.,, etc.

Geographic Domains

The geographically based top-level domains use two-letter country designations specified by the International Standards Organization (ISO 3166). For example, .us is used for the United States, .ca for Canada (not California!), .uk or .gb for the United Kingdom or Great Britain, and .il for Israel. A complete list can be found at the Internic. Using WWW, look at, and choose "Information Services", "About the Internet", and "Global Internet Information". The information about Country Codes is located at ISO 3166 Country Codes.

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