The interconnection of ISPs that forms the backbone of the internet is a complex web of fiber-optic cables with expensive networking switches and routers that direct the flow of information between source and destination hosts. Average home users are not aware of the infrastructure outside of their network. For a home user, connecting to the ISP is a fairly uncomplicated process.
The top portion of Figure 2-8 displays the simplest ISP connection option. It consists of a modem that provides a direct connection between a computer and the ISP. This option should not be used though, because your computer is not protected on the internet.
As shown in the bottom portion of Figure 2-8, a router is required to securely connect a computer to an ISP. This is the most common connection option. It consists of using a wireless integrated router to connect to the ISP. The router includes a switch to connect wired hosts and a wireless AP to connect wireless hosts. The router also provides client IP addressing information and security for inside hosts.
Figure 2-8 Connecting a Single User and Multiple Users to the Internet
Cable and DSL Connections (2.3.3)
Most home network users do not connect to their service providers with fiber-optic cables. Figure 2-9 illustrates common connection options for small office and home users. The two most common methods are as follows:
• Cable — Typically offered by cable television service providers, the internet data signal is carried on the same coaxial cable that delivers cable television. It provides a high bandwidth, always on, connection to the internet. A special cable modem separates the internet data signal from the other signals carried on the cable and provides an Ethernet connection to a host computer or LAN.
• DSL – Digital Subscriber Line — provides a high bandwidth, always on, connection to the internet. It requires a special high-speed modem that separates the DSL signal from the telephone signal and provides an Ethernet connection to a host computer or LAN. DSL runs over a telephone line, with the line split into three channels. One channel is used for voice telephone calls. This channel allows an individual to receive phone calls without disconnecting from the internet. A second channel is a faster download channel, used to receive information from the internet. The third channel is used for sending or uploading information. This channel is usually slightly slower than the download channel. The quality and speed of the DSL connection depends mainly on the quality of the phone line and the distance from the central office of your phone company The farther you are from the central office, the slower the connection.
Figure 2-9 Internet Connection Options for Individuals, Homes, and Small Businesses
Additional Connectivity Options (2.3.4)
Other ISP connection options for home users include the following:
Cellular internet access uses a cell phone network to connect. Wherever you can get a cellular signal, you can get cellular internet access. Performance will be limited by the capabilities of the phone and the cell tower to which it is connected. The availability of cellular internet access is a real benefit for people in areas that would otherwise have no internet connectivity at all, or for people who are constantly on the move. The downside of cellular connectivity is that the carrier usually meters the bandwidth usage of the connection and may charge extra for bandwidth that exceeds the contract data plan.
Satellite service is a good option for homes or offices that do not have access to DSL or cable. Satellite dishes (see Figure 2-10) require a clear line of sight to the satellite and so might be difficult in heavily wooded areas or places with other overhead obstructions. Speeds will vary depending on the contract, though they are generally good. Equipment and installation costs can be high (although check the provider for special deals), with a moderate monthly fee thereafter. Like cellular access, the availability of satellite internet access is a real benefit in areas that would otherwise have no internet connectivity at all.
An inexpensive option that uses any phone line and a modem. To connect to the ISP, a user calls the ISP access phone number. The low bandwidth provided by a dial-up modem connection is usually not sufficient for large data transfer, although it is useful for mobile access while traveling. A modem dial-up connection should only be considered when higher speed connection options are not available.
In metropolitan areas, many apartments and small offices are being connected directly with fiber-optic cables. This enables an internet service provider to provide higher bandwidth speeds and support more services such as internet, phone, and TV.
The choice of connection varies depending on geographical location and service provider availability.
Figure 2-10 Example of Satellite Internet Service Provider