M

MAC (Media Access Control) A method of controlling access to a transmission medium. For example, token ring, Ethernet, FDDI, etc.

Mailbox The location (often a flat file) where email messages are stored. On mail servers sometimes referred to as the spool file or maildrop.

MAN (Metropolitan Area Network) A data communication network covering the geographic area of a city (generally, larger than a LAN but smaller than a WAN). FDDI can provide a private MAN, while IEEE 802.6 can provide a public MAN.

MAU (Multistation Access Unit) A hub in a token ring network; each MAU supports up to eight nodes and servers and can be connected to other units to create large networks. Also Medium Attachment Unit (IEEE 802.3).

MAU Medium Attachment Unit

MB Mega Bytes

Mbps Mega Bits Per Second (one million bits per second)

MCA (Micro Channel Architecture) The basis for the IBM Micro Channel bus used in high- end models of IBM's PS/2 series of personal computers.

MCS Multicast Server

MIB (Management Information Base) A collection of objects that can be accessed via a network management protocol.

Micro-segmentation The process of dividing the network into many small Ethernet segments, each with a small client population.

MIDI Interface A device which allows the interchange of signals between a computer and a music synthesizer.

MII Media-Independent Interface

MILNET In 1984, NSF funding for the Computer Science Network led to ARPANET being split into two - MILNET for unclassified military traffic and ARPANET for research and non-military use.

MIME Multipurpose Internet Mail Extensions. A standard format to allow multimedia in mail messages.

MLID Multiple Link Interface Driver

MLT-3 Multi-Level (three-level) Encoding

Modem MODulator-dEMdulator. A device which translates digital signals from a computer into analogue signals which can be transmitted over and ordinary telephone line and vice versa.

Modulation Process by which signal characteristics are transformed to represent information. Types of modulation include frequency modulation (FM), where signals of different frequencies represent different data values.

Mosaic The original graphical web browser. Developed by the NCSA.

MP Multi-Processor Architecture for the NETBuilder II used in the 6-port Ethernet and the ATM UNI modules

MPEG A format for motion video compression defined by the Moving Photographics Experts Group.

MPOA MultiProtocol Over ATM

MPR Multiprotocol Router Plus (Novell NetWare)

MSH Multi-Services Hub (3Com)

MSNF (Multiple SNA Network Facility)

MTA Mail Transport Agent (eg sendmail). The software which handles the delivery of messages.

MTBF Mean Time Between Failures

MTTR Mean Time To Repair

MTU (Maximum Transmission Unit) The largest possible unit of data that can be sent on a given physical medium. For example, the MTU of Ethernet is 1,500 bytes.

MUA Mail User Agent. The software the user uses to retrieve and send email to or from a server.

Multicast A special form of broadcast where copies of the packet are delivered only to a subset of all possible destinations.

Multi-link PPP Multi-link PPP is a variant of PPP that addresses the additional features of compression and channel aggregation. PPP-ML, as it is known, is outlined in IETF RFC 1717.

Multiplexing A technique that enables several data streams to be sent over a single physical link; also, (ISO) a function by which one connection from a layer is used to support more than one connection to the next higher layer.

MUX (Multiplexer) A telecommunications device that funnels multiple signals onto a single channel.