The Internet is simply a large, international network of computers and smaller computer networks. Despite its definition, the Internet does differ from a Local Area Network (LAN), which is a system consisting of one server and many clients, which access stored information on the server. On the Internet, there is no central server. Instead, there are thousands of host machines which can both send and receive information to and from other hosts. In this way, each host on the Internet behaves as both a server and a client.

The actual physical network of the Internet consists of a massive web of transmission lines, each line capable of transfering a specified amount of data (this limitation is called bandwidth). This "web" of transmission lines is designed so that information from any site can reach its destination using thousands of different possible paths (see History of the Internet). When information is sent over this network, it is split into tiny packets. Each packet of information travels to its destination using a different route. When all of the packets reach their destination, the packets are regrouped to form the original piece of information. If one or more of the packets doesn't successfully make its destination, the receiving site simply asks for another copy of those packets.

Internet Addresses

Two types of addresses are used on the Internet. There are IP (Internet protocol) addresses and domain names. IP addresses are numerical addresses used by computers on the Internet to route information (such as files or e-mail) through the various computers on the Internet. Domain names are "common" names assigned to computers on the Internet. Domain names are used because numerical IP addresses (like 384.026.395) can be quite difficult for people to remember, and because of the fact that computers on the Internet often change their IP addresses, while their domain names usually remain the same.

Domain Names

As mentioned in the previous section, domain names are "common" names assigned to computers on the Internet. Each domain name has an IP address assigned to it, which is used by computers on the Internet. The domain names are used by the humans using the Internet because they are easier to remember than numerical IP addresses. They are also used because they are more permanent than IP addresses. A domain name consists of several parts: the top-level domain (TLD), the sub-domain, and the host name. The TLD is the broadest part of a domain name and comes last in the domain name. The sub-domain comes directly before the TLD. Preceeding the sub-domain can be any number of host names. In order to better demonstrate each part's function in the domain name, we will use the following example:

There are many top-level domains that you can encounter on the Internet. Some are national; that is, they may only be used by computers in a given poltical entity. Others are international, which may be used by any computer on the Internet.

Regional top-level domains are used only by computers in a given nation or political entity. They are two letters in length and are defined by the document, ISO 3166. Although the United States does have its own regional top-level domain (us), its structure is somewhat confusing and is not used very frequently. Instead, most U.S. computers on the Internet use international top-level domains (discussed below).

International top-level domains, or generic top-level domains, may be used by any computer on the Internet, regardless of its physical location. The following table shows the generic top-level domains currently avaiable, as well as their intended use:

The domain name system (DNS) is used by computers on the Internet to translate domain names into their respective IP addresses. This system is used because computers on the Internet can only use IP addresses to route information, and since each domain name's IP address can change quite frequently, a central clearinghouse for the storage of every domain name's IP address is necessary. Every DNS host throughout the world has the same information. Whenever you tell your Internet software to connect to a certian domain name, it always checks with one of the DNS computers to get the correct IP address. Only then can it actually connect to the remote Internet site. If you had to install your own TCP software, you might have noticed an entry blank for your DNS server -- where you had to enter an IP address (instead of a domain name).