Glossary
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MAU-to-MAU, HUB-to-HUB WIRING—10Base-T MAU-to-MAU or hub-to-hub
wiring generally requires a crossover cable located somewhere along the UTP cable run.
This may commonly occur at the punch-down block or between the RJ-45 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 device.
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, thereby
avoiding conflicts that occur when receiving and transmitting packets use the same pin-
out.
MANAGEMENT INFORMATION BASE (MIB)—A data base of network
configuration and performance information. The formal definition of a MIB includes the
names of the objects it contains and the type of information retained. Management
protocols such as SNMP and CMIP contain procedures for acquiring and exchanging
MIB information.
MULTIMODE FIBER—Type of fiber optic cable used for transmitting data over
relatively short distances (maximum 2 km). The fiber contains two materials with
different refractive indices and uses reflection to propagate a relatively low-intensity
signal (Class 3 or equivalent).
NETWORK SERVICES ACCESS POINT (NSAP)—OSI generic standard for a
network address consisting of 20 octets. ATM has specified E.164 for public network
addressing and the NSAP address structure for private network addresses.
PATCH PANEL—A 10Base-T patch panel may be used between a punch-down block
and UTP workstation. The patch panel generally has a female RJ-45 connector on the
front for each workstation and a Telco (RJ21) connector on the back, which is wired to a
punch-down block. This provides a convenient way for the installer or network manager
to connect the hub 10Base-T ports into the desired building locations.
PERMANENT VIRTUAL CIRCUIT (PVC)—A virtual circuit (x.25), virtual
connection (Frame Relay) or virtual channel connection (ATM) that has been
established by manual or semi-automated methods in advance of its need. Analogous to
a leased/dedicated/provisioned real circuit.
PHYSICAL MEDIUM ATTACHMENT (PMA)—The portion of the MAU that
contains the functional circuitry.
PHYSICAL SIGNALING (PLS)—That portion of the physical layer contained within
the DTE that provides the logical and functional coupling between MAU and data link
layers.
POLARITY CORRECTION—Many 10Base-T UTP ports have a polarity correction
function. If the UTP wiring has RD- and RD+ inadvertently crossed, the polarity
correction function will sample the signal and electrically swap the wires. If the TD- and
TD+ wires are crossed, the correction would occur at the MAU on the other end of the
UTP link. This occurs within a single pair and should not be confused with the crossover
cable.