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Glossary of broadband terminology: L

LAN Emulation: Typically used in LANE over ATM.
Last Mile: Refers to the local loop and is the difference between a local telephone company office and the service user; a distance of about two to three miles or three to four kilometers.
Latency: A measure of the temporal delay. Typically, in xDSL, latency refers to the delay in time between the sending of a unit of data at one end of a connection until the receipt of that unit at the destination.
Layer: OSI reference model; each layer performs certain tasks to move the information from the sender to the receiver. Protocols within the layers define the tasks for the networks but not how the tasks are accomplished.
Layer Two Tunneling Protocol: An extension to the PPP protocol that enables ISPs to operate VPNs. L2TP merges the best features of two other tunneling protocols: PPTP and L2F.
Leased Line: A telecommunications transmission circuit that is reserved by a communications provider for the private use of a customer. Also called a private line or nailed up circuit.
LISC: Local Interconnection Service Center
Loaded Pair: A twisted pair phone line with inductors, or loading coils, inserted periodically to flatten the frequency response in the 4 KHz voiceband.
Loading Coil: A device used to extend the range of a local loop for voice grade communications. They are inductors added in series with the phoneline which compensate for the parallel capacitance of the line. They benefit the frequencies in the high end of the voice spectrum at the expense of the frequencies above 3.6 KHz. Thus, loading coils prevent DSL connections.
Local Access Transport Area: The US term LATA arose out of the post-divestiture fight between the local telephone companies and AT&T over who could carry which traffic as AT&T split itself up. Roughly, a LATA maybe geographically defined as larger than a local calling area and smaller than a whole state. However, this is not a hard and fast rule -- the state of Connecticut has one LATA, for instance. The importance of the LATA is that it defines the operational areas of the US telco until it is allowed to venture beyond that boundary per the US 1996 Telecommunications Act provisions for the release of the telcos into the long haul environment.
Local Area Network: A data communications network covering a small area, usually within the confines of a building or floors within a building; a relatively high-speed computer communications network for in-building data transfer and applications. Common LAN protocols are Ethernet and Token Ring. See also Campus Area Network, Metropolitan Area Network, and Wide Area Network.
Local Exchange Carrier: One of the US telephone access and service providers that resulted from the US deregulation of telecommunications.
Local Interconnection Service Center: LISC
Local Loop: A generic term for the connection between the customer's premises (home, office, whatever) and the provider's serving central office. Historically, this has been a wireline connection; however, wireless options are increasingly available for local loop capacity. Also colloquially referred to as "the last mile" (even though the actual distance can vary).
Local Multipoint Distributed Service: A terrestrial wireless broadcasting service, principally intended for video distribution, that has been proposed by the FCC for operation in the band which operates in the same band as FSS uplink and feeder link transmissions (28 GHz). This band can supply two-way communications, meaning it could be used for interactive TV, data, and telephone services.
Long Distance: Representing the communications of information over a distance other than the local calling area. Also called "long haul" traffic.
Long Haul: A term for long distance.
Loop: Portion of the telephone network that connects the subscriber to the CO. See Local Loop.
Loopback Tests: Any tests in which a test signal is injected at one end of a circuit, is looped back at the other end, and monitored at the originating end.
Low Pass Filter: A signal filter installed in a customer premises ADSL modem (ATUR), which would not modify the low frequencies present in its input signal (the POTS transmission is sent unmodified to a phone), but would prevent the high-frequency components (data) from reaching a customer's telephone. See High Pass Filter.