Chapter 11: Voice Data Delivery and Networks

• Plain Old Telephone Service, POTS
  • The basic telephone system.
• Local Loop
  • The telephone line that leaves your house or business; it consists of either four or eight wires.
• Central Office
  • Contains the equipment that generates a dial tone, interprets the telephone number dialed, checks for special services, and connects the incoming call to the next point.
• Local Access Transport Area, LATA
  • A geographic area, such as a large metropolitan area or part of a larger state. Telephone calls that remain within a LATA are usually considered local telephone calls, while telephone calls that travel from one LATA to another are considered long-distance telephone calls.
• Trunk
  • A telephone connection used by telephone companies that carries multiple telephone signals, is usually digital and high speed, and is not associated with a telephone number.
• Modified Final Judgment
  • A court ruling in 1984 that required the divestiture, or breakup, of AT&T.
• Local Exchange Carriers, LECs
  • The name given to local telephone companies after the division of AT&T in 1984.
• Interexchange Carriers, IECs or IXc’s
  • The name given to long-distance telephone companies after the division of AT&T in 1984.
• Centrex, Central Office Exchange Service
  • A service from local telephone companies through which up-to-date telephone facilities at the telephone company’s central or local office are offered to business users so that they do not need to purchase their own facilities.
• Private Branch Exchange, PBX
  • A large computerized telephone switch that sits in a telephone room on the company property.
• Private Lines
  • A leased telephone line that requires no dialing.
• Telecommunications Act of 1996
  • A major event in the history of the telecommunications industry that, among other things, opened the door for business other than local telephone companies to offer a local telephone service.
• Competitive Local Exchange Carriers, CLECs
  • A new provider of local telephone services.
• Incumbent local Exchange Carriers, ILECs
  • A local telephone company that existed before the Telecommunications Act of 1996.
• 90 Standard
  • A 56,000-bps dial-up modem standard approved by a standards-making organization rather than a single company; it is slightly incompatible with both x2 and K56flex.
• 92 Standard
  • An improvement of the V.90 standard that provides a higher upstream data transfer rate and provides a call waiting service, in which the user’s data connection is put on hold when someone calls the user’s telephone number.
• Digital Subscriber Line, DSL
  • A technology that allows existing twisted pair telephone lines to transmit multimedia materials and high-speed data.
• Symmetric Connection
  • A type of connection in which the transfer speeds in both directions are equivalent.
• Asymmetric Connection
  • A connection in which data flows in one direction at a faster transmission rate than the data flowing in the opposite direction.
• Splinter less DSL
  • A form of digital subscriber line in which there is no POTS signal accompanying the DSL signal, thus there is no need for a splitter.
• xDSL
  • The generic name for the many forms of digital subscriber line, DSL.
• Asymmetric Digital Subscriber Line, ADSL
  • A popular form of digital subscriber line that transmits the downstream data at a faster rate than the upstream data.
• DSL Lite
  • A form of consumer DSL that has lower transmission speeds and thus lower consumer costs.
• Very High Data Rate DSL, VDSL
  • A form of digital subscriber line that is very fast, between 51 and 55 Mbps, over very short distances, less than 300 meters.
• Rate-Adaptive DSL, RADSL
  • A form of digital subscriber line in which the transfer rate can vary depending on noise levels within the telephones line’s local loop.
• Cable Modem
  • A communications device that allows high-speed access to wide area networks, such as the Internet, via a cable television connection.
• Frame Relay
  • A commercially available packet-switched network that was designed for transmitting data over fixed lines as opposed to dial-up lines.
• Permanent Virtual Circuit, PVC
  • A fixed connection between end points in a frame relay network. Unlike a telephone circuit, which is a physical circuit, a PVC is created with software routing tables, thus making it a virtual circuit.
• Layer 2 Protocol
  • A protocol that operates at the second layer, or data link layer, of the OSI seven-layer model.
• Committed Information Rate, CIR
  • The data transfer rate that is agreed on by both the customer and the carrier in a frame relay network.
• Service Level Agreement, SLA
  • A legally binding written document that can include service parameters offered in a service set up between a communications provider and its customer.
• Burst Rate
  • A rate agreed upon between a customer and a frame relay provider; this agreement allows the customer to exceed the committed information rate by a fixed amount for brief moments of time.
• Asynchronous Transfer Mode, ATM
  • A high-speed packet-switched service, like frame relay, that supports various classes of service.
• Virtual Channel Connection, VCC
  • Used in Asynchronous Transfer Mode; a logical connection that is created over a virtual path connection.