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2012-05-17

A+: Broadband Internet Services (DSL, Cable, Satellite)

Broadband Internet service is a blanket term that refers to the following Internet access methods: digital subscriber line (DSL), cable, and satellite. All of these methods provide bandwidth in excess of 300Kbps, and current implementations are two-way services, enabling you to use your telephone while accessing the Internet. Other types of broadband Internet service, including direct wireless (using microwave transceivers) and powerline, are not part of the A+ Certification exam domains, but you might encounter them in some areas.

DSL (Digital Subscriber Line), like ISDN, piggybacks on the same telephone line used by your telephone and fax machine, but it differs from ISDN in many ways. Like ISDN, DSL requires a high-quality telephone line that can carry a digital signal, but unlike ISDN, DSL is designed strictly for Internet access.

When it comes to connection speed, DSL leaves BRI ISDN in the dust. There are two major types of DSL: ADSL (Asynchronous DSL and the predominant version) and SDSL (Synchronous DSL). 

A device known as a DSL modem is used to connect your computer to DSL service. DSL modems connect to your PC through the RJ-45 (Ethernet) port or the USB port.  DSL uses the same telephone lines as ordinary telephone equipment. However, your telephone can interfere with the DSL connection. To prevent this, in some cases a separate DSL line is run from the outside service box to the computer with the DSL modem. However, if your DSL provider supports the self-installation option, small devices called microfilters are installed between telephones, answering machines, fax machines, and other devices on the same circuit with the DSL modem. Microfilters can be built into special wall plates, but are more often external devices that plug into existing phone jacks.

Some DSL connections are configured as an always-on connection similar to a network connection to the Internet. However, many vendors now configure the DSL connection as a PPPoE (point-to-point protocol over Ethernet) connection instead. A PPPoE connection requires the user to make a connection with a username and password. Windows Vista and Windows XP have native support through its Network Connection wizard. With older versions of Windows, the vendor must provide setup software.

Cable Internet
Cable Internet service piggybacks on the same coaxial cable that brings cable TV into a home or business. A few early cable ISPs used internal cable modems, which supported one-way traffic. (The cable was used for downloads and a conventional telephone line was used for uploads and page requests.) Virtually all cable Internet service today is two-way and is built upon the fiber-optic network used for digital cable and music services provided by most cable TV vendors.

Cable Internet can reach download speeds anywhere from 1Mbps up to 10Mbps or faster. Upload speeds are typically capped at 128Kbps, but some vendors now offer faster upload speeds in some plans. You can have cable Internet service without having cable TV.

Some cable TV providers use the same cable that carries cable TV for cable Internet service, while others run a separate cable to the location. When the same cable is used for both cable TV and cable Internet service, a splitter is used to provide connections for cable TV and Internet. The splitter prevents cable TV and cable Internet signals from interfering with each other. One coaxial cable from the splitter goes to the TV or set-top box as usual; the other one goes into a device known as a cable modem. Almost all cable modems are external devices that plug into a computer’s 10/100 Ethernet (RJ-45) or USB port.

A cable Internet connection can be configured through the standard Network properties sheet in Windows or with customized setup software, depending upon the ISP.
Satellite
 
Satellite Internet providers, such as HughesNet (previously known as DirecWAY, and, before that, as DirecPC), Starband, and WildBlue use dish antennas similar to satellite TV antennas to receive and transmit signals between geosynchronous satellites and computers. In some cases, you might be able to use a dual-purpose satellite dish to pick up both satellite Internet and satellite TV service.

Geosynchronous satellites orbit the Earth’s equator at a distance of 22,300 miles (approximately 35,000 kilometers). Because of their orbit and altitude, they remain in the same location in the sky at all times. In the Northern Hemisphere, you need an unobstructed view of the southern sky to make a connection. In the Southern Hemisphere, you need an unobstructed view of the northern sky to make a connection.

Satellite Internet services use external devices often called satellite modems to connect the computer to the satellite dish. They connect to the USB or Ethernet (RJ-45) port in a fashion similar to that used by DSL or cable modems.

The FCC requires professional installation for satellite Internet service because an incorrectly aligned satellite dish with uplink capabilities could cause a service outage on the satellite it’s aimed at. Setup software supplied by the satellite vendor is used to complete the process.









 

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