MAC: Media Access Control; Lower of the twosublayers of the data link layer defined by the IEEE.The MAC sublayer handles access to shared media, such as whether tokenpassing or contention will be used. See also datalink layer and LLC.
MAC address: Standardized data linklayer address that is required for every port or device that connects toa LAN. Other devices in the network use these addressesto locate specific ports in the network and to create and update routingtables and data structures. MAC addresses are 6 bytes long and are controlledby the IEEE. Also known as a hardware address, a MAC-layeraddress, or a physical address. Compare with network address.
MAE: Metropolitan Area Exchange; A MAE doesNO routing of data. The routing function is performed by the routers thatare normally connected to the MAE and which are owned and managed by theISPs. In fact, the router is the only device that connectsto a MAE. ISP hosts, as long as they act as routers,may occasionally be connected to switched ports at the MAE.
A MAE and other Internet traffic exchange points (e.g., NAPsand the CIX) are not connected to each other via dedicatedlinks. If an ISP needs to have connections to multipleMAE locations, then the ISP will build their own backbonenetwork using other appropriate high speed services. (see also peeringaggreements)
Mbps: Megabits persecond
MB: colloquially "meg"; MegaByte.
MBA: Masters of Business Administration
MBS: Maximum Burst Size; used in managing cellrate and congestion in an ATM network.
MFLOPS: Mega FLoating point OperationtionsPer Second; 1,000,000 floating point operations per second
MHz: MegaHertz equals 1,000 cycles per second
MAC: Media Access Control
MAE: Metropolitan Area Exchange; These representthe major Network Access Points, (NAP) for the Internet.
MAN: Metropolitan Area Network
Manchesterline code: A line code that maps a data bit 1 into a pulse containingboth a positive and a negative level and a data bit 0 into the same pulsewith inverted polarity.
MCI: You know... MCI, the telephone people
MCIS: Microsoft Commercial Internet System;
MCNS: Multimedia Cable Network System
MCP: Motion Compensated Prediction, (MPEG)
MC-TDMA: Multi-Channel-Time Division MultiplexingAccess
MD2: Message-Digest 2; see RSAreference page.
MD4: Message-Digest 4; see RSAreference page.
MD5: Message-Digest 5; is a one-way hash functionwhich takes a variable-length message and produces a fixed-length hash. Given the hash it is computationally impossible to find a message withthat hash; in fact one can't determine any usable information about a messagewith that hash, not even a single bit. For some one-way hash functionsit's also computationally
impossible to determine two messages which produce the same hash. Aone-way hash function can be private or public, just like an encryptionfunction. MD5 is an example of a public one-way hash function. A publicone-way hash function can be used to speed up a public-key digital signaturesystem. Rather than sign a long message which can take a long time, computethe one-way hash of the message, and sign the hash. see hashing,or RFC 1321.
MDS: Multipoint Distribution Service. Analog TV.
MDU: Multiple Dwelling Unit
Megabit: (Mb), 1,024 bits.
MegaByte: 1,048,576 bytes= 1,024 KiloBytes.
MEMS: Micro-Electronic-Mechanical Systems;MEMS devices are micro-electro-mechanical systems that can perform a widerange of physical functions in miniature. Examples are miniatureactuators, motors, movable mirrors, with a broad range of applicationsincluding sensors for activating automobile airbags, motion sensors forautomated control systems, computer displays, and medical devices.
MHEG: Multimedia Hypermedia Experts Group,(MHEG-5 page)
MHS: Message Handling System
MHz: megahertz equals 1,000,000 cycles persecond.
MIB: Management Information Base
MIB-II: Management Information Base version2
MIC: Media Interface Connector
MIDI: Musical Instrument Digital Interface
MIME: Multi-purpose Internet Mail Extensions;An Internet messages, as defined by RFC 822,consists of two parts: a header and a body. MIME defines a set of fiveextensions to RFC 822:a content type header field, a content transfer encoding header field,a MIME version header field, an optional content ID header field, and andoptional content descriptions header field. MIME has become the standardfor attaching non-text files to e-mail messages in a way that allows theattachment to be received intact over a network.
MIT: Massachusetts Institute of Technology
MLP: Multi-Layer Perception, (a neural networkarchitecture)
MMDS: Multichannel Multipoint DistributionServices; Wireless service operating between 2500-2686 MHz with currentthroughputs of 300 Kbps and 1.5 Mbps; with a range of between 35 and 70miles. Future throughput is theoretically up to 27 Mbps. Requiresline-of-sight and is affected by multipath. These frequencies havebeen used for analog TV services, and comprise thirty-one individual 6MHz television channels, and should be upgraded to digital unless sub-channelizationis being used.
MNG: Multiple-image Network Graphics
MOBAS: Multicast Output Buffered ATMSwitch
Moore's Law: The observation, madein 1965 by Intel co-founder Gordon Moore while preparing a speech, thateach new memory integrated circuit contained roughly twice as much capacityas its predecessor, and each chip was released within 18-24 months of theprevious chip. If this trend continued, he reasoned, computing power wouldrise exponentially with time.
Moore's observation still holds in 1997 and is the basis for many performanceforecasts. In 24 years the number of transistors on processor chips hasincreased by a factor of almost 2400, from 2300 on the Intel 4004 in 1971to 5.5 million on the Pentium Pro in 1995 (doubling roughly every two years).
Moore's Law has been (mis)interpreted to mean many things over the years.In particular, microprocessor performance has increased faster than thenumber of transistors per chip, doubling roughly every 18 months, due toincreases in clock rate.
Chip density in transistors per unit area has increased less quickly- a factor of only 146 between the 4004 (12 mm^2) and the Pentium Pro (196mm^2) (doubling every 3.3 years). Feature size has decreased from 10 to0.35 microns which would give over 800 times as many transistors per unit.However, the automatic layout required to cope with the increased complexityis less efficient than the hand layout used for early processors.
MOSPF: Multicast Open Shortest Path First(OSPF)
Mosaic: The first WWWbrowser that was available for the Macintosh, Windows, and UNIX all withthe same interface. Mosaic really started the popularity of the Web. Thesource-code to Mosaic has been licensed by several companies and thereare several other pieces of software as good or better than Mosaic, mostnotably, Netscape.
MoU: Memorandum of Understanding; an agreementin writing.
MP@HL: Main-Profile @ High-Level; MPEG-2Level
MP@ML: Main-Profile @ Main-Level; MPEG-2Level
MPC: A trademarked abbreviation for MultimediaPersonal Computer. The original MPC specification was developed by TandyCorporation and Microsoft as the minimum platform capable of running multimediasoftware. This has been a pseudo-successful attempt to squeeze out competitionto the Intel/Microsoft platforms, by creating a "defacto standard" throughmarketing.
MPEG: Motion Picture Expert Group; A workingcommittee which, under the auspices of the International Standards Organization,(ISO) has defined standards for the digital compressionand decompression of motion video/audio for use in computer systems. (SeeMPEG-1 and MPEG-2)
MPEG-1: standard delivers decompressiondata at 1.2 to 1.5 MB per second, allowing CD players to play full-motioncolor movies at 30 frames per second. MPEG-1 compresses at about a 50:1ratio before image degradation occurs, but compression ratios as high as200:1 are attainable. (ISO/IEC 11172)
MPEG-2: Motion Picture Expert Group version2; compressed digital motion graphics format. Building on the MPEG-1 standardis MPEG-2, which extends to the higher data rates (2-15 Mbps) needed forsignals delivered from remote sources (such as broadcast, cable, or satellite).MPEG-2 is designed to support a range of picture aspect ratios, including4:3 and 16:9.compressed digital motion graphics format. MPEG primarilydeveloped for the compression and storage of video programs. MPEG-2 extendedthe work of MPEG-1 to include such things as broadcast television and professional/studioneeds. (ISO/IEC 13818)
MPMD: Multiple Program Multiple Data
MPOA: Multiprotocol Over ATM.
MPP: Massively Parallel Processor/Processing
MRP: MHEG(Multimedia Hypermedia Experts Group) Request/Response Protocol
MSAP: MAC Service AccessPoint
MSC: MacNeal-Schwendler Corporation; NASTRANvendor.
MSEE: Masters of Science, Electrical Engineering
MSME: Masters of Science, Mechanical Engineering
MSO: Multiple System Operators
MSTV: Maximum Service Television; The Associationfor Maximum Service Television is an organization with a history of involvementin issues of channel allocation and broadcast spectrum protection.
MTA: Message Transfer Agent
MTS: Message Transfer System
multicast: Single packets copied by thenetwork and sent to a specific subset of network addresses. These addressesare specified in the destination address field. Compare with broadcastand unicast.
multicast address: Single addressthat refers to multiple network devices. Synonymous with group address.Compare with broadcast address and unicastaddress. See also multicast.
multilayer switch: Switch thatfilters and forwards packets based on MAC addressesand network addresses. A subset of LAN switch.Compare with LAN switch.
multiplexing: Scheme that allows multiplelogical signals to be transmitted simultaneously across a single physicalchannel. Compare with demultiplexing.
MVDS: Multichannel Video Distribution Systems-- MVDS is similar to MMDS but acts in the 40 GHz band.This is mainly a western European Standard.
MVS: Multiple Virtual Storage, (IBM).
MX: Mail eXchange records; DNScresource records which handle email for a particular domain.