Domain

Imagine being able to identify a single computer on the Internet out of millions, understanding the organizational method by which computers on the Internet are named, and using a powerful database to translate between human-readable names and the numbers Internet computers use to identify themselves. Once you understand the domain name system, you can understand how computers are named on the Internet and how those names are used.



Lingua Internet

• Domain: Since there are so many millions of computers on the Internet, each of which needs its own name, domains make these names unique. Two computers can share the same name as long as they are in different domains.

• Domain name: A domain name is the full human-readable name of a specific computer on the Internet. For instance, the name of the computer that Yahoo uses to store your email is Yahoomail. Every domain name corresponds to an IP address.

• Domain name system: The domain name system converts between the names people use and the IP addresses of computers on the Internet. It has three parts: the technique for converting IP addresses to domain names, the database of IP addresses and domain names, and the domain name server that actually does the conversion when asked.

• Domain name server: A domain name server is a software program (run by Internet service providers) that converts between domain names and IP addresses.

• IP address: Every computer on the Internet has an IP address that uniquely identifies it. IP address are composed of four numbers, each between 0 and 255, separated by periods, such as 205.94.168.255

• Machine name: machine name of a computer on the Internet is the first part of the domain name and differentiates that computer from others in the same domain. For example, postoffice is the machine name of postoffice.yahoomail.yahoo.com

Types of Domain

• Middle-level domain: Domain names have one or more middle-level domains to help differentiate themselves. For example, yahoomail and yahoo are both middle-level in postoffice.yahoomail.yahoo.com

• Second-level domain: The second-level domain is the middle-level domain that comes just before the top-level domain. For example, yahoo is the second-level domain in postoffice.yahoomail.yahoo.com

• Third-level domain: The Third-level domain us the middle-level domain that sits just in front of the second-level domain. For Example, yahoomail is the Third level domain in postoffice.yahoomail.yahoo.com

• Top-level domain: The top-level domain is the final part of a domain name and puts the domain name into a realtively small set of geographic and topical categories. Examples of top-level domain are .com, .edu, .gov, .ca, and .us, which identify commercial, education, government, Canandian and United State domain names, respectively. The top-level domain in postoffice.yahoomail.yahoo.com is .com, and it places that domain name in the network domain.