M

mail slots
Mail slots refer to a simple NOS service that transfers data between processes on different network computers. Unlike named pipes, a mail slot connection is created for a single data transfer, and then dropped. See named pipes.

Medium Access Control (MAC)
Unit 1: MAC is one of the media-specific IEEE 802 standards (802.3, 802.4, and 802.5) that defines the protocol and frame formats for Ethernet, Token Bus, and Token Ring. It is the lower sublayer of the Data Link Layer of the OSI model.
Unit 3: MAC refers to the Data Link Layer framing and access protocol used to transmit frames between NICs.

microsegmentation
Microsegmentation is the practice of increasing usable bandwidth by subdividing networks into smaller and smaller segments.

mode
A mode is an independent light signal traveling through an optical fiber.

multidrop
Multidrop refers to a data communication configuration where multiple terminals, printers, and workstations are located on the same media, and only one can communicate with the "master" at a given time. Multidrop is a form of unbalanced communication.

multimode fiber
Multimode fiber is a fiber optic cable thick enough to transmit several different optical signals simultaneously. Each signal is separated by the others by being reflected at different angles within the fiber. See single-mode fiber.

multiplexer (MUX)
A MUX is a device that allows multiple signals to travel over the same physical medium. See TDM and STDM.

multiprocessing
In a multiprocessing environment, multiple computers are used to process a single application.

multistation access unit (MAU)
A MAU is a device used in Token Ring networks to provide connectivity between individual workstations. It is also referred to as a Token Ring hub.

multistory trunk
A multistory trunk is a bundle of cables installed vertically in a multistory building to provide a medium for network backbones that connect network segments on multiple floors.

multitasking
The ability of a computer to execute multiple processes and applications. Although a computer with a single processing unit can only execute one instruction at a time, a multitasking OS can load and manage the execution of multiple applications by allocating computer processing cycles to each application in sequence. The perceived result is the simultaneous processing of multiple applications or tasks. There are two kinds of multitasking: preemptive and cooperative. With preemptive multitasking, the OS is in charge and manages system resource allocation and task scheduling. With cooperative multitasking, applications are in charge and share resources.

multithreading
A thread is a process within an application that executes a specific operation. A computer capable of multithreading is one that supports multiple threads, essentially allowing applications to multitask within themselves.