The User's Computer Connects to a Modem

• The beginning point of an Internet experience lies not in the Internet itself, but in the local laptop or desktop computer. This local machine begins the Internet connection process by using special software -- either built into the operating system itself or included in a software package -- to create a network connection using the computer's modem, wireless adapter or Ethernet connector. In some cases, the local computer is connected to a local area network (LAN) that shares a common Internet gateway, or it may be connected directly to a modem.
  
  

The Modem Connects to a Service Provider

• Regardless of the local configuration, the modem modulates data from the computer or LAN to send upstream. If the computer uses a dial-up modem, the modem initiates a telephone call to the service provider; broadband connections like DSL and cable modems are somewhat different, however, in that they are always connected and do not require a connection routine each time the Internet is accessed. No matter how the modem connects to the service provider, its primary function is to modulate data into a format suitable for transmission to the service provider and demodulate data coming in from the upstream connection. Depending on the technology in use, the format of modulation used by the modem -- a word that is composed of the first few letters of the words "Modulate" and "Demodulate" -- may differ slightly, but the modem's purpose is always to connect to the service provider.
  
  

The Service Provider Relays Data

• Except for very large Internet service providers (ISPs), providers generally subscribe to a high-bandwidth feed from a company with direct access to the Internet backbone. Using Internet Protocol (IP) routing (the same routing protocol used by a local computer's LAN), the ISP transfers data between the user and the remote connection over Gigabit Ethernet, Asynchronous Transfer Mode (ATM), or Frame Relay commercial-grade data pipes.
  
  

IP Drives the Internet

• As data packets flow between the user and the Internet server, several steps -- known as "hops" -- are passed along the way: the user's computer; the user's LAN; the modem connection to the ISP; the ISP connection to the Internet backbone; and the final connection to the destination server (in some cases, a data packet may make several additional stops along the way as it travels past any upstream providers for the destination server). Data are able to quickly and easily traverse this entire connection using Internet Protocol, a form of routing that breaks data into small blocks of information, labels them with an address and sends them on their way. Each user is assigned one of these addresses -- known as an IP address -- as is each Internet server (when a user types a domain name such as www.ehow.com into a web browser, a background process queries special servers to determine, or resolve, the IP address of the server). With the local and server IP addresses known, all data packets are assigned an address for their destination and sent to the upstream host; as the data packets work their way from the source to the destination, the IP address is read by the host and forwarded along to the next step in the path to the destination. When the server issues a response, data packets are returned using the same IP address and transfer process. Because these steps happen very quickly, they are mostly transparent to the end user.