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11.2 | |
The Application Layer | |
| 11.2.2 | |
DNS |
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The Internet is built on a hierarchical
addressing scheme. This scheme allows for routing to be based on
classes of addresses rather than based on individual addresses. The
problem this creates for the user is associating the correct address
with the Internet site. It is very easy to forget an IP address to a
particular site because there is nothing to associate the contents of
the site with the address. Imagine the difficulty of remembering the
IP addresses of tens, hundreds, or even thousands of Internet sites.
A domain naming system was developed in order to associate the contents of the site with the address of that site. The Domain Name System (DNS) is a system used on the Internet for translating names of domains and their publicly advertised network nodes into IP addresses. A domain is a group of computers that are associated by their geographical location or their business type. A domain name is a string of characters, number, or both. Usually a name or abbreviation that represents the numeric address of an Internet site will make up the domain name. There are more than 200 top-level domains on the Internet, examples of which include the following:
There are also generic names, which examples include the following:
See Figure
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for a
detailed explanation of these domains. 
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