Discuss a dedicated line and briefly describe the different types of dedicated lines.

Question

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Answer 1

Student responses will vary, but should be drawn from the following information from the text.

A dedicated line is a type of always-on physical connection that is established between two communications devices. Businesses often use dedicated lines to connect geographically distant offices. Dedicated lines can be either analog or digital. Digital lines increasingly are connecting home and business users to networks around the globe because they transmit data and information at faster rates than analog lines.

Digital dedicated lines include cable television lines, DSL, ISDN lines, FTTP, T-carrier lines, and ATM.

Cable: The cable television (CATV) network provides high-speed Internet connections, called cable Internet service. The CATV signal enters a building through a single line, usually a coaxial cable. This cable connects to a modem (discussed in the next section), which typically attaches to your computer via an Ethernet cable. Home and small business users often subscribe to cable Internet service.

DSL: DSL (Digital Subscriber Line) transmits on existing standard copper phone wiring. Some DSL installations include a dial tone, providing users with both voice and data communications. These DSL installations often require that filters be installed to reduce noise interference when voice communications share the same line. DSL is a popular digital line alternative for the small business or home user.

ADSL is a popular type of DSL. ADSL (asymmetric digital subscriber line) is a type of DSL that supports faster transfer rates when receiving data (the downstream rate) than when sending data (the upstream rate). ADSL is ideal for Internet access because most users download more information from the Internet than they upload.

ISDN: Not as widely used today as in the past, ISDN (Integrated Services Digital Network) is a set of standards for digital transmission of data over standard copper phone lines. With ISDN, the same phone line that could carry only one computer signal now can carry three or more signals at once through the same line, using a technique called multiplexing.

FTTP: FTTP, which stands for Fiber to the Premises, uses fiber-optic cable to provide extremely high-speed Internet access to a user's physical permanent location.

• FTTH (Fiber to the Home) provides home users with Internet access via fiber-optic cable.
• FTTB (Fiber to the Building) refers to small businesses that use fiber-optic cables to access the Internet.

With FTTP service, an optical terminal at your location receives the signals and transfers them to a router connected to a computer. As the cost of installing fiber decreases, more homes and businesses are expected to choose FTTP.

T-Carrier: A T-carrier line is any of several types of long-distance digital phone lines that carry multiple signals over a single communications line. Whereas a standard phone line carries only one signal, digital T-carrier lines use multiplexing so that multiple signals share the line. T-carrier lines provide very fast data transfer rates. Only medium to large companies usually can afford the investment in T-carrier lines because these lines are so expensive.

The most popular T-carrier line is the T1 line. Businesses often use T1 lines to connect to the Internet. Home and small business users purchase fractional T1, in which they share a connection to the T1 line with other users. Fractional T1 is slower than a dedicated T1 line, but it also is less expensive.

Users who do not have other high-speed Internet access in their areas can opt for fractional T1. With fractional T1 lines, the data transfer rates become slower as additional users are added. A T3 line is equal in speed to 28 T1 lines. T3 lines are quite expensive. Main users of T3 lines include large corporations, phone companies, and ISPs connecting to the Internet backbone. The Internet backbone itself also uses T3 lines.

ATM: ATM (Asynchronous Transfer Mode) is a service that carries voice, data, video, and media at very high speeds. Phone networks, the Internet, and other networks with large amounts of traffic use ATM. Some experts predict that ATM eventually will become the Internet standard for data transmission, replacing T3 lines.