Objectives
Upon completion of this chapter, you will be able to answer the following questions:
- What are the ISP connectivity options?
- What are the purpose and characteristics of network virtualization?
- How do you configure mobile devices for wireless connectivity?
Key Terms
This chapter uses the following key terms. You can find the definitions in the Glossary.
Digital Subscriber Line (DSL) page 274
Infrastructure as a Service (IaaS) page 277
Platform as a Service (PaaS) page 277
Software as a Service (SaaS) page 277
software-defined networking (SDN) page 283
Introduction (14.0.1)
Are you storing music, photos, files, and other data in the cloud? Many companies offer this service to their customers. They can do this because of virtualization and the cloud. In addition to storage, the cloud can provide many other services. Read on to find out more about this ever-growing aspect of networking.
ISP Connectivity Options (14.1)
An Internet service provider (ISP) provides a link between a home network and the Internet. An ISP can be the local cable provider, a landline telephone service provider, the cellular network that provides your smartphone service, or an independent provider who leases bandwidth on the physical network infrastructure of another company.
ISP Services (14.1.1)
Many ISPs also offer additional services to their contract subscribers, as shown in Figure 14-1. These services can include email accounts, network storage, and website hosting and automated backup or security services.
Figure 14-1 ISP Services
ISPs are critical to communications across the global Internet. Each ISP connects to other ISPs to form a network of links that interconnects users all over the world. ISPs are connected in a hierarchical manner that ensures that Internet traffic generally takes the shortest path from the source to the destination.
The Internet backbone is like an information superhighway that provides high-speed data links to connect the various service provider networks in major metropolitan areas around the world. The primary medium that connects the Internet backbone is fiber-optic cable. This cable is typically installed underground to connect cities within continents. Fiber-optic cables also run under the sea to connect continents, countries, and cities.
ISP Connections (14.1.2)
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 14-2 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 from the Internet.
Figure 14-2 Connecting a Single User and Multiple Users to the Internet
As shown in the bottom portion of Figure 14-2, 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 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.
Cable and DSL Connections (14.1.3)
Most home network users do not connect to their service providers with fiber-optic cables. Figure 14-3 illustrates common connection options for small office and home users. The two most common methods are as follows:
Figure 14-3 Internet Connection Options for Individuals, Homes, and Small Businesses
- 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—A 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 depend 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.