Appendix G. Glossary
G-6 ATLAS 550 User Manual 61200305L1-1
IXC
IntereXchange Carrier. Phone companies that connect LECs.
kbps
Kilobits per second. 1,000 bits per second.
LAN
Local area network. A group of computers and peripheral devices connected by a communications
channel, limited by distance.
leased line
A telecommunication facility or link reserved for the exclusive use of one customer. Also called a ded-
icated line.
LEC
Local Exchange Carrier. Provides local access to public data and phone networks.
LED
Light emitting diode. Alphanumeric characters that glow when supplied with a specified voltage.
Link Integrity Poll
A poll that occurs each T391 seconds to determine the state of the connection to the frame relay switch.
LLC2
Logical Link Control Type 2. Upper portion of the Data Link layer (layer 2) that handles flow control
and error control.
LMI
Standard published by the Frame Relay Consortium in 1990 to create a defined interface on the UNI.
The Consortium was composed of Cisco Systems, DEC, Nortel, and StrataCom, and is commonly
referred to as the Group of Four. LMI has become a generic term to indicate the type of frame relay sig-
nalingusedandcouldbeusedtomeanAnnexAorAnnexD.
local loop
In telephony the wire pair that connects a subscriber to a phone company end office, typically contain-
ing two wires. Four-wire local loops are common, however, especially with leased voice grade circuits.
loopback
A diagnostic procedure where data is sent to the device being tested, and the output of the device is
fed directly back to its input, looped around, and the returning data is checked against that which was
sent.
MAC Address
Data link address that is unique for every device that gets connected to a LAN. Devices on the LAN
usetheseaddressestoupdateroutingtables.
Mbps
Mega bits per second. A measure of the amount of information travelling across a network or commu-
nications link.
MIB
Management information base. The MIB is an index to the organized data stored within a network
device.
