Networking Definitions

This glossary explains the meaning of key words and phrases that information technology (IT) and business professionals use when discussing networking and related software products. You can find additional definitions by visiting WhatIs.com or using the search box below.

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  • J

    Jabber

    Jabber is an initiative to produce an open source, XML-based instant messaging platform.

  • jabber (in networks)

    In networks, a jabber is any device that is handling electrical signals improperly, usually with negative results for the rest of the network.

  • jam

    In an Ethernet network, a jam is a signal from one device to all other devices that a collision has occurred. Specifically, the device was trying to send a frame while another device was also trying to put a frame on the line.

  • Jini

    Jini (pronounced "GEE-nee" like the Arabic word for "magician") is a network architecture concept that Sun Microsystems calls "spontaneous networking." Using Jini, users will be able to plug printers, storage devices, speakers or any kind of device directly into a network and every other computer, device and user on the network will know that the new device has been added and is available.

  • Joint Academic Network (JANET)

    In the United Kingdom, JANET (Joint Academic Network) is the main backbone network for the UK university system of academic and research computers.

  • jumbo frames

    A jumbo frame is an Ethernet frame with a payload greater than the standard maximum transmission unit (MTU) of 1,500 bytes. 

  • K

    K56flex

    Rockwell Corporation's K56flex modem chipset gave users the capability to receive data on ordinary phone lines at 56 Kbps (thousand bits per second).

  • Kazaa Media Desktop (KMD)

    Kazaa (its full name is Kazaa Media Desktop or KMD) is a decentralized Internet peer-to-peer (P2P) file-sharing program owned by Sharman Networks.

  • Kbps (kilobits per second)

    In the U.S., Kbps stands for kilobits per second (thousands of bits per second) and is a measure of bandwidth (the amount of data that can flow in a given time) on a data transmission medium.

  • keystone jack

    A keystone jack is a female connector used in data communications, particularly local area networks (LANs).

  • kHz (kilohertz)

    The kilohertz, abbreviated kHz, is a unit of alternating current (AC) or electromagnetic (EM) wave frequency equal to one thousand hertz (1,000 Hz).

  • KVM switch (keyboard, video, mouse switch)

    A KVM (keyboard, video, mouse) switch is a hardware device that allows a user to control multiple computers from a single keyboard, video display monitor and mouse.

  • L

    lambda switching (photonic switching, or wavelength switching)

    Lambda switching (sometimes called photonic switching, or wavelength switching) is the technology used in optical networking to switch individual wavelengths of light onto separate paths for specific routing of information.

  • LAN party

    A LAN party is a gathering in which gamers (devotees of computer games) gather to share a local area network (LAN) and participate in extended gaming sessions of popular games such as Quake, Doom, or Wolfenstein.

  • LAN server

    A local area network (LAN) server is a program (and by implication usually the computer it runs in) that "serves" the resources (files, storage, application programs, printers, and other devices) for a number of attached workstations.

  • LANDesk Client Manager (LDCM)

    LDCM (LANDesk Client Manager) is a software product from Intel that lets a system administrator for a local area network () see the configurations and monitor the status of personal computer on the LAN. LDCM is an implementation of the Desktop Management Interface (DMI) standard established by the Desktop Management Task Force, an industry group.

  • last-mile technology

    Last-mile technology is any telecommunications technology that carries signals from the broad telecommunication backbone along the relatively short distance (hence, the "last mile") to and from the home or business.

  • layer 2

    Layer 2 refers to the Data Link layer of the commonly-referenced multilayered communication model, Open Systems Interconnection (OSI).

  • Layer Two Tunneling Protocol (L2TP)

    Layer Two Tunneling Protocol (L2TP) is an extension of the Point-to-Point Tunneling Protocol (PPTP) used by an Internet service provider (ISP) to enable the operation of a virtual private network (VPN) over the Internet.

  • Learning Path: Network and Web Site Administration

    NETWORK AND WEB SITE ADMINISTRATION....network operations center (NOC) - internetworking - firewall - proxy server - DMZ - NAT - EGP - BGP - peering - colocation - IGP - DHCP - network operating system - Novell Directory Services (NDS) - nslookup - NNTP - SNMP - e-mail - POP3 - Simple Mail Transfer Protocol (SMTP) - X.400 Messaging - e-mail reflector - list server - file sharing - Web server - Network File System (NFS) - finger - ping - traceroute - TTL (time-to-live) - GDMO - ICMP - Apache (server) - X.500 Directory Service - Lightweight Directory Access Protocol (LDAP) - Windows Internet Naming Service (WINS) - Universal Naming Convention - UDDI - vital product data - root server system - access control list - public key infrastructure - linkrot - Kermit - Internet traffic sites - ping storm - KVM switch - sliding windows - denial-of-service attack - ghost imaging View other topics for self-study by visiting our Guide to the Learning Paths.

  • Learning Path: Network Infrastructure

    NETWORK INFRASTRUCTURE...infrastructure - backbone - network access point (NAP)- vBNS - Internet 2 - MAE - peering - router - switch - bridge - hub - stackable hub - repeater - brouter - aggregator - gateway - point-of-presence (POP) - colocation - CSU/DSU - terminal server - host - network operations center - X terminal - network-attached storage (NAS) - storage area network View other topics for self-study by visiting our Guideto the Learning Paths.

  • Learning Path: Telephony and Wide Area Networks

    TELEPHONY AND WIDE AREA NETWORKS...circuit - PSTN - Plain Old Telephone Service (POTS) - telephone jacks - dial-up - acoustic coupler - modem - 56flex - 56 Kbps (x2) - handshaking - V.xx standards - local loop - central office - LIDB - dedicated line - BOC - RBOC - Intelligent Network (IN) - Advanced Intelligent Network (AIN) - Signaling System 7 (SS7) - EWSD - erlang (measure of line usage) - frame - frame relay - frame relay access device (FRAD) - ATM - 2600 - ISDN - B-channel - D-channel - terminal adapter - BISDN - HDLC - IDSL - PABX - Direct Inward Dialing (DID) - Automatic Number Identification (ANI) - Dialed Number Identification Service (DNIS) - permanent virtual circuit (PVC) - switched virtual circuit - DSLAM - Voice over IP - VoxML - CAPI - TAPI - splitter - splitterless (DSL) - ATU-R - digital loop carrier View other topics for self-study by visiting our Guide to the Learning Paths.

  • LEC (local exchange carrier)

    LEC (local exchange carrier) is the term for a public telephone company in the U.S. that provides local service.

  • line doubler

    A line doubler is an electronic device that converts analog or digital television (TV) video signals into a format suitable for display on a computer monitor.

  • line information database (LIDB)

    A line information database (LIDB) is a database maintained by the local telephone company that contains subscriber information, such as a service profile, name and address, and credit card validation information.

  • Link Control Protocol (LCP)

    In the Point-to-Point Protocol (PPP), the Link ControlProtocol (LCP) establishes, configures, and tests data-link Internet connections.

  • Link Quality Source Routing (LQSR)

    LQSR (Link Quality Source Routing) is a routing protocol for wireless mesh networks. The protocol was developed by Microsoft for use with their MCL (Mesh Connectivity Layer) technology, which facilitates the interconnection of computers into a mesh network using WiFi or WiMax wireless services. The LQSR protocol is based on DSR (Dynamic Source Routing).

  • link-load balancer (link balancer)

    A link load balancer, also called a link balancer, is a network appliance that distributes in-bound and out-bound traffic to and from multiple Internet Service Providers (ISPs) links.

  • LMDS (Local Multipoint Distribution System)

    LMDS (Local Multipoint Distribution System) is a system for broadband microwave wireless transmission direct from a local antenna to homes and businesses within a line-of-sight radius, a solution to the so-called last-mile technology problem of economically bringing high-bandwidth services to users.

  • load balancing

    Load balancing is a technique used to distribute workloads uniformly across servers or other compute resources to optimize network efficiency, reliability and capacity.

  • loading coil

    A loading coil is an induction device placed on a local loop longer than 18,000 feet that carries analog signals.

  • local access and transport area (LATA)

    LATA (local access and transport area) is a term in the U.S. for a geographic area covered by one or more local telephone companies, which are legally referred to as local exchange carriers (LECs).

  • local area network (LAN)

    A local area network (LAN) consists of computers and peripherals that share a common communications line or wireless link to a server. LANs are typically located within a distinct geographic area in an office or other facility.

  • local loop

    In telephony, a local loop is the wired connection from a telephone company's central office in a locality to its customers' telephones at homes and businesses.

  • Local Number Portability (LNP)

    Local Number Portability (LNP) is the ability of a telephone customer in the U.S. to retain their local phone number if they switch to another local telephone service provider.

  • Location Routing Number (LRN)

    In the U.S., a Location Routing Number (LRN) is a 10-digit number in a database called a Service Control Point (SCP) that identifies a switching port for a local telephone exchange.

  • location-based service (LBS)

    A location-based service (LBS) is a software application for a mobile device that requires knowledge about where the mobile device is located.

  • Logical Link Control layer (LCL layer)

    The Logical Link Control (LCL) layer is one of two sublayers of the Data-Link layer in the Open Systems Interconnection (OSI) model of communication. The LCL layer is concerned with managing traffic (flow and error control) over the physical medium.

  • logical network

    A logical network is one that appears to the user as a single, separate entity although it might in fact be either just a part of a larger network or an entity connecting multiple networks. A logical network is defined by its IP addressing scheme.

  • logical router

    A logical router is a configured partition of a traditional network hardware, or "physical," router.

  • long-haul optics

    Long-haul optics refers to the transmission of visible light signals over optical fiber cable for great distances, especially without or with minimal use of repeaters.

  • loopback

    In telephone systems, a loopback is a test signal sent to a network destination that is returned as received to the originator. The returned signal may help diagnose a problem.

  • loopback test

    A loopback test is a test in which a signal in sent from a communications device and returned (looped back) to it as a way to determine whether the device is working right or as a way to pin down a failing node in a network.

  • loose coupling

    Loose coupling is a method of interconnecting the components in a system or network so that those components, also called elements, depend on each other to the least extent practicable... (Continued)

  • M

    MAC address (Media Access Control address)

    In a local area network (LAN) or other network, the MAC (Media Access Control) address is your computer's unique hardware number.

  • MAE

    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 interconnecting traffic between Internet service providers (ISPs).

  • mail user agent (MUA)

    A mail user agent (MUA) is a program that allows you to receive and send e-mail messages; it's usually just called an e-mail program.

  • managed network services

    Managed network services are networking applications, functions and services that enterprises outsource to be remotely operated, monitored and maintained by a managed service provider (MSP).

  • Manchester encoding

    In data transmission, Manchester encoding is a form of digital encoding in which data bits are represented by transitions from one logical state to the other.

  • Manufacturing Message Specification (MMS)

    The Manufacturing Message Specification (MMS) is an international standard that defines the ways in which control information is transferred among intelligent devices and systems such as computers and robots... (Continued)

  • master

    A master, in a technological context, is a device that controls one or more other devices.

  • master/minion (formerly master/slave)

    In computer networking, master/slave is a model for a communication protocol in which one device or process (known as the master) controls one or more other devices or processes (known as slaves).

  • 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.

  • 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.

  • MBone (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).

  • Mbps (megabits per second)

    Megabits per second (Mbps) are a unit of measurement for bandwidth and throughput on a network. Each megabit is equal to 1 million bits.

  • MDI/MDIX (medium dependent interface/MDI crossover)

    MDI/MDIX is a type of Ethernet port connection using twisted pair cabling.

  • mean opinion score (MOS)

    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.

  • Media Access Control layer (MAC layer)

    In the Open Systems Interconnection (OSI) model of communication, the Media Access Control layer is one of two sublayers of the Data Link Control layer and is concerned with sharing the physical connection to the network among several computers.

  • media access management

    In the Open Systems Interconnection (OSI) communication reference model, media access management is performed by the Media Access Control (MAC) sublayer of the Data-Link Layer.

  • media attachment unit (MAU)

    MAU is also sometimes used as the abbreviation for the token ring network multistation access unit (MSAU).

  • Media Gateway Control Protocol (MGCP)

    Media Gateway Control Protocol (MGCP), also known as H.248 and Megaco, is a standard protocol for handling the signaling and session management needed during a multimedia conference.

  • megahertz (MHz)

    The megahertz, abbreviated MHz, is a unit of alternating current (AC) or electromagnetic (EM) wave frequency equal to one million hertz (1,000,000 Hz).

  • Mesh Connectivity Layer (MCL)

    Mesh Connectivity Layer (MCL) is a technology that allows a computer user to connect to a wireless mesh network that uses Wi-Fi or WiMax. The wireless mesh network can be connected to the Internet through a single computer using a leased T-1 line or broadband satellite connection, allowing all network users high-speed Internet access.

  • Metcalfe's Law

    Metcalfe's Law is expressed in two general ways: The number of possible cross-connections in a network grow as the square of the number of computers in the network increases.

  • Metro Ethernet

    Metro Ethernet is the use of Carrier Ethernet technology in metropolitan area networks (MANs)... (Continued)

  • 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).

  • MFSK (multiple frequency shift keying)

    MFSK (multiple frequency shift keying), also called multi-frequency shift keying, is a method of signal modulation in which discrete audio tone bursts of various frequencies convey digital data.

  • MHz

    The megahertz, abbreviated MHz, is a unit of alternating current (AC) or electromagnetic (EM) wave frequency equal to one million hertz (1,000,000 Hz).

  • microsegmentation

    Microsegmentation, also known as security segmentation, is a process used by network security professionals to break a network into smaller pieces in order to make it easier to keep the overall system secure.

  • Microsoft Network Access Protection (NAP)

    Network access protection (NAP), introduced with Windows Server 2008, is Microsoft’s approach to controlling access to a network based on a determination of each device’s health.

  • microwave

    The term microwave refers to electromagnetic energy having a frequency higher than 1 gigahertz (billions of cycles per second), corresponding to wavelength shorter than 30 centimeters.

  • mil

    mil is one of the top-level domain names that can be used when choosing a domain name.

  • millimeter wave (MM wave)

    Millimeter wave (also millimeter band) is the band of spectrum between 30 gigahertz (Ghz) and 300 Ghz. Researchers are testing 5G wireless broadband technology on millimeter wave spectrum.

  • MILNET

    MILNET was the name given to the part of ARPANET, the forerunner of the Internet, that was designated for nonclassified U.S. military use.

  • Mininet

    Mininet is a software emulator for prototyping a large network on a single machine. 

  • modem doubling

    Modem doubling is an inexpensive way for a user who wants a fast Internet connection, but can only connect with an analog telephone line, to use two 56kbps modems to double their bandwidth.

  • modem error-correcting protocols

    The protocols that modems agree on and use for checking and correcting transmission errors have evolved toward accuracy, speed, and efficiency since 1978 when the Xmodem protocol became a de facto standard.

  • modem lights (AA)

    This page provides a description of the abbreviations and meanings of each of the lights that describe the "handshaking" between a computer modem and the UART chip in a computer.

  • modulation

    Modulation is the process of converting data into radio waves by adding information to an electronic or optical carrier signal.

  • Molex

    In business since 1938, Molex manufactures electronic, electrical, and optical fiber connectors.

  • moonbounce or Earth-Moon-Earth (EME)

    Moonbounce, also called Earth-Moon-Earth (EME), is a form of wireless communication in which the moon is used as a passive satellite.

  • Morse code

    Morse code is a method of sending text messages by keying in a series of electronic pulses, usually represented as a short pulse (called a "dot") and a long pulse (a "dash").

  • MOSPF (Multicast Open Shortest Path First)

    MOSPF (Multicast Open Shortest Path First) is an extension to the OSPF (Open Shortest Path First) protocol that facilitates interoperation between unicast and multicast routers... (Continued)

  • MPLS-TP (MPLS Transport Profile)

    The Multiprotocol Label Switching Transport Profile (MPLS-TP) is a protocol extension of MPLS designed to speed up and shape network traffic in operator transport networks.

  • mrouter (multicast router)

    An mrouter, or multicast router, is a router program that distinguishes between multicast and unicast packets and determines how they should be distributed along the Multicast Internet (sometimes known as the Multicast Backbone or MBone).

  • mu-Law

    Mu-Law is the standard codec (compression/decompression) algorithm for pulse code modulation (PCM) from the CCITT (Consultative Committee for International Telephone and Telegraph).

  • multi-tapping

    Multi-tapping is an older procedure used to enter text using a telephone keypad.

  • multi-user MIMO

    Multi-user MIMO (MU-MIMO) is a wireless communication technology that uses multiple antennas to improve communication by creating multiple connections to the same device at the same time

  • multicast

    Multicast is communication between a single sender and multiple receivers on a network.

  • Multicast Dissemination Protocol (MDP)

    The Multicast Dissemination Protocol (MDP) is a communications protocol for one-to-many transmissions in wired or wireless networks.

  • Multichannel Multipoint Distribution Service (MMDS)

    Multichannel Multipoint Distribution Service (MMDS) is a broadcasting and communications service that operates in the ultra-high-frequency (UHF) portion of the radio spectrum between 2.1 and 2.7 GHz.

  • multichassis multilink PPP (MMP)

    Multichassis multilink PPP (MMP) is an extension of multilink PPP (MP) in which the subscriber can consist of more than one computer... (Continued)

  • multihomed

    Multihomed describes a computer host that has multiple IP addresses to connected networks.

  • multilink PPP

    Multilink PPP is a communications protocol that enables a personal computer (PC) to use two PPP (Point-to-Point Protocol) communications ports as if they were a single port of greater bandwidth... (Continued)

  • multimode fiber

    In optical fiber technology, multimode fiber is optical fiber that is designed to carry multiple light rays or modes concurrently, each at a slightly different reflection angle within the optical fiber core.

  • multiplexing

    Multiplexing is the simultaneous sending of multiple information streams over a communications medium as a single, complex signal that is then recovered at the receiving end.

  • Multiprotocol Label Switching (MPLS)

    Multiprotocol Label Switching (MPLS) is a protocol-agnostic routing technique designed to speed up and shape traffic flows across enterprise wide area and service provider networks.

  • multistation access unit (MSAU)

    A multistation access unit (MSAU) is a hub or concentrator that connects a group of computers ('nodes' in network terminology) to a token ring local area network.

  • mutex (mutual exclusion object)

    In computer programming, a mutex (mutual exclusion object) is a program object that is created so that multiple program thread can take turns sharing the same resource, such as access to a file.

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