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Glossary
Local Exchange Carrier (LEC): The local phone company which provides local (i.e., not long distance) transmission
services. Aka "telco". LECs provide T1 or FT1 access to LDCs (unless the T1 circuit is completely intra-LATA). Inter-LATA T1
circuits are made up of a combination of Access and Long Haul facilities.
Local Management Interface (LMI): A specification for frame relay equipment that defines status information exchange.
Local Loop: A transmission path, typically twisted-pair wire, between an individual subscriber and the nearest public
telecommunications network switching center. The wires provide ISDN service, but require an NT1 at the user end and an
LT at the network end. (AKA, "loop" or "subscriber loop".)
Logical Link Control (LLC2): In a local area network, the protocol that governs the exchange of transmission frames
between data stations independently of how the transmission medium is shared. The LLC2 protocol was developed by the
IEEE 802 committee and is common to all LAN standards.
Logical Unit (LU): A type of network accessible unit that enables end users to gain access to network resources and
communicate with each other.
Long Haul: The T1 element that connects to the Access portion of the long distance company's (LDC's) central office. The
LDC is commonly called the point of presence (POP). Each LDC has a number of POPs, located throughout the country.
The LDC is also called an IEC (Inter Exchange Carrier).
Long Haul Communications: The type of phone call reaching outside of a local exchange (LE).
M
Management Information Base (MIB): A database of network management information used by the Common
Management Information Protocol (CMIP) and the Simple Network Management Protocol (SNMP).
Megacom: An AT&T service with a normal WATS line (typically T1) between the customer premise and the AT&T serving
class 4 CO are the customer's responsibility.
MegaLink: BellSouth's leased T1 service.
Message: Associated with such terms as packet, frame, and segment. 1. In information theory, an ordered series of
characters intended to convey information. 2. An assembly of characters and sometimes control codes that is transferred as
an entry from an originator to one or more recipients.
Modem: A communications device that enables a computer to transmit information over a telephone line. It converts the
computer's digital signals into analog signals to send over a telephone line and converts them back to digital signals at the
receiving end. Modems can be internal and fit into an expansion slot, or external and connect to a serial port.
Multi-Link/PPP (ML/PPP): A 'bandwidth on demand' technology that allows one logical PPP connection to add additional
channels (as in a second ISDN channel) when the bandwidth is needed (however the vendor defines that situation). It may
also be used with leased lines when the total bandwidth needed exceeds the available line speed - a form of inverse
muxing.
Multiplexer (Mux): 1. A device that takes several input signals and combines them into a single output signal in such a
manner that each of the input signals can be recovered. 2. A device capable of interleaving the events of two or more
activities or capable of distributing the events of an interleaved sequence to the respective activities. 3. Putting multiple
signals on a single channel.
Multiprotocol: A device that can interoperate with devices utilizing different network protocols.
Multithreading: The ability of a software system to be able to handle more than one transaction concurrently. This is
contrasted to the case where a single transaction is accepted and completely processed before the next transaction
processing is started.
N
Nailed Connection: A permanent or dedicated circuit of a previously switched circuit or circuits.
Nailed-up Circuit: A semipermanent circuit established through a circuit-switching facility for point-to-point connectivity.
NAK (Negative Acknowledgment): Communications code used to indicate that a message was not properly received, or
that a terminal does not wish to transmit. Contrast with ACK.
Network: A group of computers connected by cables or other means and using software that enables them to share
equipment, such as printers and disk drives to exchange information.
Node: Any point within a network which has been assigned an address.
MTPSR1-202ST
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