Glossary
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JABBER LOCK-UP
—The MAU’s ability to automatically inhibit the
transmit data from reaching the medium if the transmit data time exceeds a
specified duration. This duration is in the range of 20 ms to 150 ms. Jabber
lock-up protects the medium from being overrun with data packets from a
possibly defective device.
JAM
—This is a term used to describe the collision reinforcement signal
output by the repeater to all ports. The jam signal consists of 96 bits of
alternating 1s and 0s. The purpose is to extend a collision sufficiently so that
all devices cease transmitting.
JITTER
—The fluctuation of the data packet in respect to a standard clock
cycle. Jitter is undesirable and must be minimized.
LINK SEGMENT
—The link segment of coaxial cable is a segment which
has no MAU devices but links two LAN devices together such as repeaters.
LINK TEST
—In 10BASE-T Ethernet there is a link test function that
validates the UTP link. This consists of a pulse transmitted from point A on
one pair and validated at point B. Point B also transmits a pulse on the second
pair to be validated by point A. These pulses occur during media idle states
(in between packets).
MANAGED MODULE
— An intelligent repeater in a department
concentrator chassis that makes management data available to the Master.
MANAGEMENT AGENT
—Software that is used to view hub activity and
set hub variables.
MASTER
—A repeater in the top-most position in a department
concentrator chassis that contains and downloads the management agent
software to Backup and Slaves. The Master contains the only active image of
the management agent and controls the management functions of the Backup
and Slaves.
MAU
—See Medium Attachment Unit
MAU-to-MAU, HUB-to-HUB WIRING
—10BASE-T MAU-to-MAU or
hub-to-hub wiring generally requires a cross-over cable located somewhere
along the UTP cable run. This may commonly occur at the punch-down block
or between the RJ45 wall receptacle and the workstation.
MAU/TRANSCEIVER
—An Ethernet transceiver is a MAU. A 10BASE-T
MAU interfaces the UTP media to an AUI port on a workstation, repeater,
bridge, or other Ethernet devices.
MDI/MDI-X
—See Medium Dependent Interface
MEDIUM ATTACHMENT UNIT (MAU)
—In a LAN, a device used in a
data station to couple the DTE to the transmission medium.
MEDIUM DEPENDENT INTERFACE (MDI)
—The mechanical and
electrical interface between the trunk cable medium and the MAU. MDI-X is
another version of the interface that enables like devices to connect, using
different pin-outs, avoiding conflicts that occur when receiving and
transmitting packets use the same pin-out.
