On a local area network (LAN) or other network, the MAC (Media Access Control) address is your computer's unique hardware number. (On an Ethernet LAN, it's the same as your Ethernet address.) When you're connected to the Internet from your computer (or host as the Internet protocol thinks of it), a correspondence table relates your IP address to your computer's physical (MAC) address on the LAN.
The MAC address is used by the Media Access Control sublayer of the Data-Link Layer (DLC) layer of telecommunication protocol . There is a different MAC sublayer for each physical device type. The other sublayer level in the DLC layer is the Logical Link Control sublayer.
A macro virus is a computer virus that "infects" a Microsoft Word or similar application and causes a sequence of actions to be performed automatically when the application is started or something else triggers it. Macro viruses tend to be surprising but relatively harmless. A typical effect is the undesired insertion of some comic text at certain points when writing a line. A macro virus is often spread as an e-mail virus. A well-known example in March, 1999 was the Melissa virus virus.
A MAE (pronounced MAY), originally an abbreviation for Metropolitan Area Exchange and now a service mark of MCI WorldCom, is a major center in the United States for switch traffic between Internet service providers (ISP ). There are two major MAEs, MAE-East in the Washington, D.C. area and MAE-West in the San Jose, California area. MAE-East interconnects all of the major ISPs and also those from Europe. MAE-West interconnects ISPs in the Silicon Valley area. These two points along with several interconnection points previously identified by the National Science Foundation as network access points (network access point) form what is sometimes considered the national commercial Internet backbone . In addition to MAE-East and MAE-West, there are five regional "Tier-2" MAEs: in Chicago, Dallas, Houston, Los Angeles, and New York. Additional MAEs appear to be in the planning stages. The MAEs and their services, originally developed by MFS Communications, are now owned and operated by MCI WorldCom.
A MAE can be viewed as a giant local area network (LAN) switch. (In fact, the two major MAEs use an Fiber Distributed-Data Interface switch.) The only ISP device that can interconnect to a MAE switch is a router or a computer host acting as a router. The ISPs work out their own peering agreements and manage their own routing tables. Routers at the two major MAEs need very large routing tables. Cisco's 7xxx series routers are examples of such routers. The regional MAEs consist of an Ethernet switch and an FDDI concentrator. Smaller routers (such as Cisco's 4500-M) are required. The MAEs offer colocation space for ISP equipment on their premises.
A mail bomb is the sending of a massive amount of e-mail to a specific person or system. A huge amount of mail may simply fill up the recipient's disk space on the server or, in some cases, may be too much for a server to handle and may cause the server to stop functioning. In the past, mail bombs have been used to "punish" Internet users who have been egregious violators of netiquette (for example, people using e-mail for undesired advertising, or spam).
Mail bombs not only inconvenience the intended target but they are also likely to inconvenience everybody using the server. Senders of mail bombs should be wary of exposing themselves to reciprocal mail bombs or to legal actions.
Mainframe is an industry term for a large computer, typically manufactured by a large company such as IBM for the commercial applications of Fortune 1000 businesses and other large-scale computing purposes. Historically, a mainframe is associated with centralized rather than distributed computing. Today, IBM refers to its larger processors as large servers and emphasizes that they can be used to serve distributed users and smaller servers in a computing network.
Main storage is the main area in a computer in which data is stored for quick access by the computer's processor. This term originated in the days of the mainframe computer to distinguish the more immediately accessible data storage from auxiliary storage. On today's computers, especially personal computers and workstations, the term random access memory (RAM) is usually used instead of main storage, and the hard disk, diskette, and CD-ROM collectively describe auxiliary storage.
An earlier term for main storage was core in the days when the main data storage device contained ferrite cores.
Like listserv, Majordomo (from Latin: "master of the house") is a small program that automatically redistributes e-mail to names on a mailing list. Users can subscribe to a mailing list by sending an e-mail note to a mailing list they learn about; Majordomo will automatically add the name and distribute future e-mail postings to every subscriber. (Requests to subscribe and unsubscribe are sent to a special address so that other subscribers do not see these requests.)
Majordomo is written in the Practical Extraction and Reporting Language language. Although it originated in the UNIX culture, Majordomo can be run on any operating system platform with a Perl interpreter.
A makefile is used with the UNIX make utility to determine which portions of a program to compile. A makefile is basically a script that guides the make utility to choose the appropriate program files that are to be compiled and linked together.
The make utility keeps track of the last time files were updated so that it only updates the files containing changes. However, all of the files that are dependent on the updated files must be compiled as well, which can be very time-consuming. With the help of makefile, the make utility automates this compilation to ensure that all files that have been updated - and only those - are compiled and that the most recent versions of files are the ones linked to the main program, without requiring the user to perform the tasks separately.
A makefile contains three types of information for the make program: a target (the name of what the user is trying to construct); the rules (commands that tell how to construct the target from the sources) and a dependency (the reason that the target should be constructed, which is usually because it is out of date in respect to its components). To create a makefile, the user makes a file containing shell commands and names it "makefile." The commands are executed according to the rules in the makefile when the user types "make" while in the directory containing the file.
Mammoth is a magnetic tape and drive system used for computer data storage and archiving. The tapes measure eight millimeters (8 mm) across. A helical scanning technique is used to optimize the data transfer and storage rates.
A Mammoth cartridge can hold 40 gigabytes (GB) of data when compression is used. The compression algorithm is known as improved data recording capability (IDRC ). The maximum extent of compression is about 2:1. The Mammoth drive can transfer data at speeds of up to 3 megabytes per second (Mbps) without compression, and 6 Mbps with compression.
Mammoth is one of several high-volume, high-speed tape drives developed in recent years. Some examples of competing devices include the linear tape open (LTO) drive, the advanced intelligent tape (AIT) drive, and the DLT drive.
Man - Metropolitan Area Network:
In voice communications, particularly Internet telephony, the mean opinion score (MOS) provides a numerical measure of the quality of human speech at the destination end of the circuit. The scheme uses subjective tests (opinionated scores) that are mathematically averaged to obtain a quantitative indicator of the system performance.
Compressor/decompressor (codec) systems and digital signal processing (DSP) are commonly used in voice communications because they conserve bandwidth . But they also degrade voice fidelity. The best codecs provide the most bandwidth conservation while producing the least degradation of the signal. Bandwidth can be measured using laboratory instruments, but voice quality requires human interpretation.
To determine MOS, a number of listeners rate the quality of test sentences read aloud over the communications circuit by male and female speakers. A listener gives each sentence a rating as follows: (1) bad; (2) poor; (3) fair; (4) good; (5) excellent. The MOS is the arithmetic mean of all the individual scores, and can range from 1 (worst) to 5 (best).
Managed Service Provider - MSP:
A managed service provider (MSP) provides delivery and management of network-based services, applications, and equipment to enterprises, residences, or other service providers. Managed service providers can be hosting companies or access provider s that offer services that can include fully outsourced network management arrangements, including advanced features like IP telephony, messaging and call center, virtual private network (VPNs), managed firewall s, and monitoring/reporting of network servers. Most of these services can be performed from outside a company's internal network with a special emphasis placed on integration and certification of Internet security for applications and content. MSPs serve as outsourcing agents for companies, especially other service providers like ISPs, that don't have the resources to constantly upgrade or maintain faster and faster computer networks.
In addition to such basic communication service as leased line wide area network (WAN) and frame relay service, an MSP can manage and integrate a range of activities associated with enterprise networks. The range of outsourcing services includes basic transport and access, managed premises, Web hosting , VPN, unified messaging, video networking, or other more sophisticated services. The market for managed services is forecast to grow about 20 percent annually, according to The Yankee Group, due largely to the need for enterprises to be more flexible and timely in getting to market and communicating with customers.
Managed service providers sometimes are referred to as management service providers, which also manage information technology services for companies. However, some industry experts say managed service providers provide a broader range of services than management service providers, which tend to limit themselves to monitoring services for servers, routers, firewalls, and other applications. Management service providers typically deliver infrastructure management services on a subscription basis, similar to the model used by application service providers (ASPs). They most commonly offer network- and application-monitoring services to e-businesses.
Management Information Base - MIB:
A management information base (MIB) is a formal description of a set of network objects that can be managed using the Simple Network Management Protocol (SNMP). The format of the MIB is defined as part of the SNMP. (All other MIBs are extensions of this basic management information base.) MIB-I refers to the initial MIB definition; MIB-II refers to the current definition. SNMPv2 includes MIB-II and adds some new objects.
There are MIBs (or more accurately, MIB extensions) for each set of related network entities that can be managed. For example, there are MIB definitions specified in the form of Requests for Comments (RFCs) for AppleTalk, domain name system (DNS), Fiber Distributed-Data Interface, and RS-232C network objects. Product developers can create and register new MIB extensions. Companies that have created MIB extensions for their sets of products include Cisco, Fore, IBM, Novell, QMS, and Onramp.
MAPI - Messaging Application Program Interface:
See Messaging Application Program Interface.
Mapuccino is a Java applet or small program that can show a visual map of how a Web site is organized. For example, you may want a map view of your own site. Mapuccino will quickly assess your Web files and create map views of it that you can view and, if you wish, save. Mapuccino let you alternate between a horizontal map view, a vertical map view, a regular Table of Contents (that looks like a Windows directory/file hierarchy), and a goldfish view. Since the nodes on the map represent individual HTML pages, they are also hyperlink to the pages, enabling you to use the map as a way to navigate or explore a site.
Using Mapuccino, you can also select a site and specify a map of just that part of the site that meets your information criteria. Mapuccino was developed by IBM's Haifa Research Lab and is currently a laboratory demonstration. You can see the demonstration at IBM's Web site.
Markup refers to the sequence of characters or other symbols that you insert at certain places in a text or word processing file to indicate how the file should look when it is printed or displayed or to describe the document's logical structure. The markup indicators are often called "tags." For example, this particular paragraph is preceded by a:
(or paragraph tag)
so that it will be separated by an empty line from the preceding line.
There is now a standard markup definition for document structure (or really a description of how you can define markup) in the Standard Generalized Markup Language (SGML).
Markup can be inserted by the document creator directly by typing the symbols in, by using an editor and selecting prepackaged markup symbols (to save keystrokes), or by using a more sophisticated editor that lets you create the document as you want it to appear (this is called a WYSIWYG editor).
1) Apart from information technology, matrix (pronounced MAY-triks) has a number of special meanings. From the Latin word for womb (in turn from mater or mother), a matrix is either the intercellular substance of a tissue, the material in which a fossil is embedded, or a mold from which a relief surface is made in printing or phonograph manufacturing.
2) In mathematics and computer science, a matrix is a set of numbers laid out in tabular form (in rows and columns). From this meaning, a less formal meaning is derived of a complex of lines intersecting at right angles.
3) In cyberculture, the Internet and other networks that flow into it are altogether sometimes called "the matrix." In William Gibson's science-fiction novel, Neuromancer ," the matrix" is a vast sea of computing resources that can be visualized by the user, is accessible at many levels, and is lit up more intensely in the areas of greatest activity. The hero, Case, "jacks in" to the matrix through wiring that is (perhaps, since it's not entirely clear) integrated with his brain and explores the matrix with a "deck" or computer console that provides a holographic view.
Maximum Segment Size - MSS:
The maximum segment size (MSS) is the largest amount of data, specified in bytes, that a computer or communications device can handle in a single, unfragmented piece. For optimum communications, the number of bytes in the data segment and the header must add up to less than the number of bytes in the maximum transmission unit (MTU).
The MSS is an important consideration in Internet connections, particularly Web browsing. When the Internet's Transmission Control Protocol (TCP ) is used to achieve an Internet connection, the computers being connected must each agree on, and then set, the MTU size acceptable to both. Typical MTU size in TCP for a home computer Internet connection is either 576 or 1500 bytes. Headers are 40 bytes long; the MSS is equal to the difference, either 536 or 1460 bytes. In some instances the MTU size is less than 576 bytes, and the data segments must therefore be smaller than 536 bytes.
As data is routed over the Internet, it must pass through multiple gateway router s. Ideally, each data segment can pass through every router without being fragmented. If the data segment size is too large for any of the routers through which the data passes, the oversize segment(s) are fragmented. This slows down the connection speed as seen by the computer user. In some cases the slowdown is dramatic. The likelihood of such fragmentation can be minimized by keeping the MSS as small as reasonably possible. For most computer users, the MSS is set automatically by the operating system.
Maximum Transmission Unit - MTU:
A Maximum Transmission Unit (MTU) is the largest size packet or frame, specified in octets (eight-bit bytes), that can be sent in a packet- or frame-based network such as the Internet. The Internet's Transmission Control Protocol uses the MTU to determine the maximum size of each packet in any transmission. Too large an MTU size may mean retransmissions if the packet encounters a router that can't handle that large a packet. Too small an MTU size means relatively more header overhead and more acknowledgements that have to be sent and handled. Most computer operating systems provide a default MTU value that is suitable for most users. In general, Internet users should follow the advice of their Internet service provider (ISP) about whether to change the default value and what to change it to.
In Windows 95, the default MTU was 1500 octets (eight-bit bytes), partly because this is the Ethernet standard MTU. The Internet de facto standard MTU is 576, but ISPs often suggest using 1500. If you frequently access Web sites that encounter routers with an MTU size of 576, you may want to change to that size. (Apparently some users find that changing the setting to 576 improves performance and others do not find any improvement.) The minimum value that an MTU can be set to is 68.
For more recent Windows systems, the operating system is able to sense whether your connection should use 1500 or 576 and select the appropriate MTU for the connection. For protocols other than TCP, different MTU sizes may apply.
MBone - aka Multicast Internet:
The MBone, now sometimes called the Multicast Internet, is an arranged use of a portion of the Internet for Internet Protocol (IP) multicasting (sending files - usually audio and video streams - to multiple users at the same time somewhat as radio and TV programs are broadcast over airwaves). Although most Internet traffic is unicast (one user requesting files from one source at another Internet address), the Internet's IP protocol also supports multicasting, the transmission of data packet s intended for multiple addresses. Since most IP servers on the Internet do not currently support the multicasting part of the protocol, the MBone was set up to form a network within the Internet that could transmit multicasts. The MBone was set up in 1994 as an outgrowth of earlier audio multicasts by the Internet Engineering Task Force (IETF) and has multicast a number of programs, including some well-publicized rock concerts.
The MBone consists of known servers (mostly on UNIX workstations) that are equipped to handle the multicast protocol. tunneling is used to forward multicast packets through routers on the network that don't handle multicasting. An MBone router that is sending a packet to another MBone router through a non-MBone part of the network encapsulates the multicast packet as a unicast packet. The non-MBone routers simply see an ordinary packet. The destination MBone router unencapsulates the unicast packet and forwards it appropriately. The MBone consists of a backbone with a mesh topology which is used by servers that redistribute the multicast in their region in a star topology. The MBone network is intended to be global and includes nodes in Europe.
The channel bandwidth for MBone multicasts is 500 kilobits per second and actual traffic is from 100-300 kilobits depending on content. MBone multicasts usually consist of streaming audio and video.
MCM - Multi Carrier Modulation:
See Multi Carrier Modulation.
MD2 is an earlier, 8-bit version of MD5, an algorithm used to verify data integrity through the creation of a 128-bit message digest from data input (which may be a message of any length) that is claimed to be as unique to that specific data as a fingerprint is to the specific individual. MD2, which was developed by Professor Ronald L. Rivest of MIT, is intended for use with digital signature applications, which require that large files must be compressed by a secure method before being encrypted with a secret key, under a public key cryptosystem. According to the RFC document, it is "computationally infeasible" that any two messages that have been input to the MD5 algorithm could have as the output the same message digest, or that a false message could be created through apprehension of the message digest. MD2, MD4 (a later version), and MD5, the latest version, have similar structures, but MD2 was optimized for 8-bit machines, in comparison with the two later formulas, which are optimized for 32-bit machines. The MD5 algorithm is an extension of MD4, which the critical review found to be fast, but possibly not absolutely secure. In comparison, MD5 is not quite as fast as the MD4 algorithm, but offers much more assurance of data security.
MD4 is an earlier version of MD5, an algorithm used to verify data integrity through the creation of a 128-bit message digest from data input (which may be a message of any length) that is claimed to be as unique to that specific data as a fingerprint is to the specific individual. MD4, which was developed by Professor Ronald L. Rivest of MIT, is intended for use with digital signature applications, which require that large files must be compressed by a secure method before being encrypted with a secret key, under a public key cryptosystem. According to the MD5 specification, it is "computationally infeasible" that any two messages that have been input to the MD5 algorithm could have as the output the same message digest, or that a false message could be created through apprehension of the message digest. MD2, an earlier 8-bit version, MD4, and MD5, the latest version, have similar structures, but MD2 was optimized for 8-bit machines, in comparison with the two later formulas, which are optimized for 32-bit machines. The MD5 algorithm is an extension of MD4, which the critical review found to be fast, but possibly not absolutely secure. In comparison, MD5 is not quite as fast as the MD4 algorithm, but offers much more assurance of data security.
MD5 is an algorithm that is used to verify data integrity through the creation of a 128-bit message digest from data input (which may be a message of any length) that is claimed to be as unique to that specific data as a fingerprint is to the specific individual. MD5, which was developed by Professor Ronald L. Rivest of MIT, is intended for use with digital signature applications, which require that large files must be compressed by a secure method before being encrypted with a secret key, under a public key cryptosystem. MD5 is currently a standard, Internet Engineering Task Force (IETF) Request for Comments (RFC ) 1321. According to the standard, it is "computationally infeasible" that any two messages that have been input to the MD5 algorithm could have as the output the same message digest, or that a false message could be created through apprehension of the message digest. MD5 is the third message digest algorithm created by Rivest. All three (the others are MD2 and MD4) have similar structures, but MD2 was optimized for 8-bit machines, in comparison with the two later formulas, which are optimized for 32-bit machines. The MD5 algorithm is an extension of MD4, which the critical review found to be fast, but possibly not absolutely secure. In comparison, MD5 is not quite as fast as the MD4 algorithm, but offers much more assurance of data security.
MDI/MDIX - Medium Dependent Interface:
MDI/MDIX is a type of Ethernet port connection using twisted pair cabling. The MDI (for Medium Dependent Interface) is the component of the media attachment unit (MAU) that provides the physical and electrical connection to the cabling medium. An MDIX (for MDI crossover ) is a version of MDI that enables connection between like devices. MDI ports connect to MDIX ports via straight-through twisted pair cabling; both MDI-to-MDI and MDIX-to-MDIX connections use crossover twisted pair cabling.
Mean Opinion Score - MOS:
See Mean Opinion Score.
Mean Swap Between Failure - MSBF:
Mean-swap-between-failure (MSBF) is a measure used by at least one company to express the reliability of an automated tape library system in which a robot is used to automatically swap tape cartridge s when needed. The Quantum ATL IntelliGrip feature for its tape system controls the gripping force of the robot allowing it to firmly grasp the tape cartridge and gently swap it with another. According to Quantum ATL, its automatic tape cartridge system has an MSBF of 2,000,000 (that is, two million swaps between any two failures).
1) As a measure of computer processor storage and real and virtual memory, a megabyte (abbreviated MB) is 2 to the 20th power byte, or 1,048,576 bytes in decimal notation.
2) According to the IBM Dictionary of Computing, when used to describe disk storage capacity and transmission rates, a megabyte is 1,000,000 bytes in decimal notation.
According to the Microsoft Press Computer Dictionary, a megabyte means either 1,000,000 bytes or 1,048,576 bytes. According to Eric S. Raymond in The New Hacker's Dictionary, a megabyte is always 1,048,576 bytes on the argument that bytes should naturally be computed in powers of two.
Messaging Application Program Interface - MAPI:
Messaging Application Program Interface) is a Microsoft Windows program interface that enables you to send e-mail from within a Windows application and attach the document you are working on to the e-mail note. Applications that take advantage of MAPI include word processors, spreadsheets, and graphics applications. MAPI-compatible applications typically include a Send Mail or Send in the File pulldown menu of the application. Selecting one of these sends a request to a MAPI server.
MAPI consists of a standard set of C language functions that are stored in a program library known as a dynamic link library (DLL). Developers who are using Microsoft's Active Server Page (ASP) technology access the MAPI library by using Microsoft's Collaboration Data Objects (CDO). The CDO library comes with Microsoft's Internet Information Server (IIS). MAPI functions can be accessed by Visual Basic developers through a Basic-to-C translation layer.
Eudora, one of the most popular e-mail programs, includes a MAPI server. To activate the Eudora MAPI server, select Options from the Tools pulldown menu and then double-click on MAPI and specify whether MAPI should always be active or whether it should be active only when Eudora is running. Microsoft Exchange and possibly some other programs may require that you turn the MAPI server off when they are in use.
Metropolitan Area Network - Man:
A Metropolitan Area Network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). It is also used to mean the interconnection of several local area networks by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network.
Examples of metropolitan area networks of various sizes can be found in the metropolitan areas of London, England; Lodz, Poland; and Geneva, Switzerland. Large universities also sometimes use the term to describe their networks.
MIB - Management Information Base:
See Management Information Base.
MOS - Mean Opinion Score:
See Mean Opinion Score.
MSBF - Mean Swap Between Failure:
See Mean Swap Between Failure.
MSP - Managed Service Provider:
See Managed Service Provider.
MSP - Mass Storage Provider:
A MSP (Mass Storage Provider) is a data storage company, which specializes in storing and facilitating very large qualities of data. In today's standards, that means volumes or partitions greater then 1 terabyte in size. Companies will tend to use a MSP to help store their archive computer data, or data that many need to be preserved for many years. An MSP also provides off site capabilities for the data.
MSS - Maximum Segment Size:
See Maximum Segment Size.
M-theory or also known as "The Mother of All Theories", is a supposed magical linear algebra matrix stated to have been developed by Ed Witten and Paul Townsend of Princeton and Cambridge respectively.
MTU - Maximum Transmission Unit:
See Maximum Transmission Unit.
Multi Carrier Modulation - MCM:
Multi-carrier modulation (MCM) is a method of transmitting data by splitting it into several components, and sending each of these components over separate carrier signals. The individual carriers have narrow bandwidth, but the composite signal can have broad bandwidth.
The advantages of MCM include relative immunity to fading caused by transmission over more than one path at a time (multipath fading), less susceptibility than single-carrier systems to interference caused by impulse noise, and enhanced immunity to inter-symbol interference. Limitations include difficulty in synchronizing the carriers under marginal conditions, and a relatively strict requirement that amplification be linear.
MCM was first used in analog military communications in the 1950s. Recently, MCM has attracted attention as a means of enhancing the bandwidth of digital communications over media with physical limitations. The scheme is used in some audio broadcast services. The technology lends itself to digital television, and is used as a method of obtaining high data speeds in asymmetric digital subscriber line (ADSL) systems. MCM is also used in wireless local area networks (WLANs).
Also see orthogonal frequency-division multiplexing (OFDM), frequency-division multiplexing (FDM), and time-division multiplexing (TDM).