Glossary M

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  • M: Mutual inductance
  • MA: Millampere (one thousandth of an ampere)
  • MAC: See Media Access Control
  • Main 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 storage.
  • MAN: See Metropolitan Area Network
  • 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.
  • Manchester 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 Automation Protocol
  • Mapping: Redirecting local resources to network resources
  • 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 Access Unit
  • 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 connection.
  • 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.
  • Mbyte: See Megabyte
  • MCA: See Micro Channel Architecture
  • 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.
  • Mechanical Splicing: Joining two fibers together by mechanical means to enable a continuous signal. Elastomeric splicing is one example of mechanical splicing.
  • 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 Control (LLC).
  • 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 regulations.
  • Meg: Shortened prefix for one million. Usually short for Megabyte.
  • 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. Mbps.)
  • Megahertz: (MHz) Unit of frequency equal to one million hertz.
  • Memory: Where data may be entered, stored & retrieved.
  • 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 (MOTIS).
  • Metropolitan Area Network: (MAN) A network capable of high-speed data communications over distances up to about 80 kilometers.
  • MHS: See Message Handling System
  • MHz: See Megahertz
  • MIB: See Management Information Base
  • Micro 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 power.
  • 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 network.
  • MIPS: See Million Instructions Per Second
  • 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 Information Service
  • MJ: See Modulator Jack
  • MMJ: See Modified Modular Jack
  • Mode: A single electromagnetic field pattern within an optical fiber. Often used to describe a light path through a fiber.
  • 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.
  • Modified 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 one.
  • 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 contacts.
  • Modulation: The alteration of a signal's frequency, phase, or amplitude.
  • 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 resources.
  • MS-DOS: See Disk Operating System
  • MSS: See Maximum Segment Size
  • MTBF: See Mean Time Between Failures
  • MTD: See Maximum Transmission Distance
  • MTTR: See Mean Time To Repair
  • MTU: See Maximum Transmission Unit
  • Multi-protocol: A network node which can support more than one protocol router; can forwarded packets for more than one network layer protocol
  • 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 other MAUs.
  • 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
  • Multimedia: An application that communicates to more than one of the human sensory receptors or applications that communicate information by more than one means.
  • 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 use.
  • Multiplex: To put two or more signals into a single channel.
  • 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 carrier frequencies.
  • Multipoint Line: A data communication link interconnecting several DTE's. Multipoint lines are always dedicated.
  • Multiport Repeater: A repeater, either stand alone or connected to standard Ethernet cable, for interconnecting up to eight thin Ethernet segments.
  • 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.
  • Mutual Capacitance: Capacitance between two conductors when all other conductors are connected together.
  • Mylar: DuPont trademark for polyethylene terephtalate (polyester) film.
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