Glossary M0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
- M: Mutual
- MA: Millampere (one thousandth of an
- MAC: See Media Access Control
Cross-connect: A cross-connect for first level backbone cables, entrance
cables & equipment cables.
- Main Ring: Consists of the cable between
the MAUs in a Token Ring network. It does not include the cable between the
MAUs & their attaching devices.
- Mainframe: A large, high-performance
multi-user computer, capable of the largest computing tasks & information
- MAN: See Metropolitan Area
- Management Information Base: (MIB) A
database of network management information used by CMIP (Common Management
Information Protocol) & SNMP (Simple Network Management Protocol)
- Management Information Service: (MIS) An MIS professional
is one who is involved in the technology, products & service of making
information available to the decision makers who need it.
Encoding: Digital encoding method that describes a bit value by the
transition between two signals & that is self-clocking.
- Manufacturing Automation Protocol: (MAP) A version of the
OSI (Open Systems Interconnection) model for manufacturing environments
developed by General Motors.
- MAP: See Manufacturing
- Mapping: Redirecting local resources to
- Mark: Presence of signal. In telegraphy, a mark
represents the closed condition or current flowing. A mark impulse is
equivalent to a binary 1.
- MAU: See Multi-station
- Maximum Segment Size: (MSS) The
largest segment that one TCP module can transmit to another TCP module. Maximum
segment size can be negotiated at the establishment of a TCP
- Maximum Transmission Distance: (MTD)
The maximum allowable length of a Token Ring network. It is a function of the
number of MAUs, the number of wiring closets & the wire gauge. See charts in
the Token Ring Technical Information section for calculation values.
- Maximum Transmission Unit: (MTU) The maximum sized packet
that IP can transmit through any local area network or link.
- MCA: See Micro
- Mean Time Between
Failures: (MTBF) A stated or published period of time for which a user may
expect a device to operate before a failure occurs.
- Mean Time To Repair: (MTTR) The average time required to
perform corrective maintenance on a failed device.
Splicing: Joining two fibers together by mechanical means to enable a
continuous signal. Elastomeric splicing is one example of mechanical
- Media Access Control: (MAC) A media
specific access-control protocol within the IEEE 802 specifications; currently
includes variations for the Token Ring, Token Bus & CSMA/CD; the lower
sub-layer of the IEEE’s link layer (OSI) which compliments the Logical Link
- Media Filter: The adapter that connects a PC with a
Token Ring adapter card to an unshielded twisted pair wiring system. The media
filter limits the amount of radiated energy to meet FCC
- Meg: Shortened prefix for one million. Usually short for
- Mega: Prefix meaning million.
- Megabyte: (Mbyte, Meg, or M) 1,0458,576 bytes, equal to
1024 kilobytes; basic unit of measurement of mass storage; also used in
describing (primarily parallel) data-transfer rates as a function of time (e.g.
- Megahertz: (MHz) Unit of frequency equal to
one million hertz.
- Memory: Where data may be entered, stored &
- Message: One of the transition stages of data as it
travels over the different TCP/IP layers.
- Message Framing: The
technique of identifying the beginning & the ending of a message. It is usually
done by using Data Link Control Characters, such as, STX & ETX.
- Message Handling System: (MHS) The standard defined by the
CCITT as X.400 & by the ISO as Message Oriented Text (Interchange Standard
- Metropolitan Area Network: (MAN) A network
capable of high-speed data communications over distances up to about 80
- MHS: See Message Handling
- MHz: See Megahertz
- MIB: See
Management Information Base
Channel Architecture: (MCA) IBM's proprietary bus architecture that offers
improved performance over ISA (Industry Standard Architecture) & is used
primarily in PS/2 computer systems.
- Microcomputer: A small or
"desktop" computer of relatively limited computing
- Microphonics: Noise caused by mechanical excitation of a
system component. In a single-conductor microphone cable, for example,
microphonics can be caused by the shield rubbing against the dielectric as the
cable is flexed.
- Microprocessor: A computer (capable of performing
arithmetic, logic, or controlled functions) constructed on a single LSI (Large
Scale Integrated) chip.
- Microsoft-Disk Operating System: See Disk Operating System
- MIF: See Minimum Internetworking Functionality
- Million Instructions Per Second: (MIPS) A general comparison
gauge of a computer's raw processing power.
- Mini-Manufacturing Automation Protocol: (Mini-MAP) A
version of MAP consisting of only physical, link, &
application layers intended for lower-cost process-control networks. With
Mini-MAP device with a token can request a response from an address device;
unlike a standard MAP protocol, the addressed Mini-MAP device need not wait for
the token to respond.
- Mini-MAP: See Mini-Manufacturing Automation Protocol
- Minimum Internetworking Functionality: (MIF) A general
principle within the ISO that calls for minimum local area network station
complexity when interconnecting with resources outside the local area
- MIPS: See Million Instructions Per
- Mirroring: A fault tolerance method in which a backup data
storage device maintains data identical to that on the primary device & can
replace the primary if it fails.
- MIS: See Management
- MJ: See Modulator
- MMJ: See Modified Modular
- Mode: A single electromagnetic field pattern within an
optical fiber. Often used to describe a light path through a
- Modem: (MOdulator-DEModulator) A device that converts digital
& analog signals.
- Modem Eliminator: A device used to connect a local
terminal & a computer port instead of the pair of modems they would ordinarily
need; allows DTE-to-DTE data & control signal connections otherwise not easily
achieved by standard cables or connectors.
Modular Jack: (MMJ) These are the 6 pin connectors used to connect serial
terminal lines to terminal devices. MMJ jacks can be distinguished from the
similar RJ12 jacks by having a side locking tab, rather than a center mounted
- Modular Plug: A male telecommunications interface connector as
specified in IEC 603-7 & FCC Part 68 Subpart F. Modular plugs may have 4, 6, or
8 contact positions. Not all positions need be equipped with
- Modulation: The alteration of a signal's frequency, phase,
- Modulator Jack: (MJ) A jack used for
connecting voice cable to a faceplate, as for a telephone.
- Mount: The
method in NFS & other networks by which nodes access network
- MS-DOS: See Disk Operating
- MSS: See Maximum Segment
- MTBF: See Mean Time Between
- MTD: See Maximum Transmission
- MTTR: See Mean Time To
- MTU: See Maximum Transmission
- Multi-protocol: A network node which can support more than
one protocol router; can forwarded packets for more than one network layer
- Multi-station: A network allowing more than one station, or
network node, to be attached to the same link.
- Multi-station Access Unit: (MAU) The wiring concentrate or
used in Token Ring networks. The MAU contains ports for connecting up to 8
workstations, as well as RI (Ring-In) & RO (Ring-Out) ports for connection to
- Multi-user Software: An application designed for
simultaneous access by two or more network nodes. It typically employs file
and/or record locking.
- Multicast: An address for a selection of nodes
in a network, or the message sent to a selection of nodes
An application that communicates to more than one of the human sensory
receptors or applications that communicate information by more than one
- Multimode Fiber: An optical fiber that will allow many bound
modes to propagate. The fiber may be either a graded index or step index fiber.
Multimode optical fibers have a much larger core than single mode fibers. See
also optical fiber cable.
- Multiple Routing: The process of sending a
message to more than one recipient, usually when all destinations are specified
in the header of the message.
- Multiple-access: A means of controlling
transmissions over a wire or other media that allows more than one sender to
transmit over that media at different times, thus sharing its
- Multiplex: To put two or more signals into a single
- Multiplexing: The combining of multiple data channels onto a
single transmission medium; any process through which a circuit normally
dedicated to a single user can be shared by multiple users; typically, user
data streams are interleaved on a bit or byte basis or separated by different
- Multipoint Line: A data communication link
interconnecting several DTE's. Multipoint lines are always
- Multiport Repeater: A repeater, either stand alone or
connected to standard Ethernet cable, for interconnecting up to eight thin
- Multiprocessor: A computer with more than one
Central Processing Unit (CPU) that can be accessed simultaneously by an
operating system adapted to this architecture.
- Multitasking: The
process of swapping from one task to another without losing track of either.
Usually accomplished by time slicing any shared resources.
Capacitance: Capacitance between two conductors when all other conductors
are connected together.
- Mylar: DuPont trademark for polyethylene
terephtalate (polyester) film.