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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  • D

    data plane (DP)

    The data plane (sometimes known as the user plane, forwarding plane, carrier plane or bearer plane) is the part of a network that carries user traffic.

  • data streaming

    Data streaming is the continuous transfer of data at a steady, high-speed rate. To facilitate the need for real-time analytics from disparate data sources, many companies have replaced traditional batch processing with streaming data architectures that can accommodate batch processing.

  • Data-Link layer

    The data link layer is the protocol layer in a program that handles the moving of data into and out of a physical link in a network.

  • datagram

    A datagram is, to quote the Internet's Request for Comments 1594, "a self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between this source and destination computer and the transporting network."

  • DCE (Distributed Computing Environment)

    In network computing, DCE (Distributed Computing Environment) is an industry-standard software technology for setting up and managing computing and data exchange in a system of distributed computers.

  • DECT (Digital Enhanced Cordless Telecommunications)

    Unlike the analog cordless phones you may have in your home, DECT (Digital Enhanced Cordless Telecommunications) is a digital wireless telephone technology that is expected to make cordless phones much more common in both businesses and homes in the future.

  • deep packet inspection (DPI)

    Deep packet inspection (DPI) is an advanced method of examining and managing network traffic.

  • delay-tolerant network

    A delay-tolerant network is a network designed to operate effectively over extreme distances such as those encountered in space communications or on an interplanetary scale... (Continued)

  • demarc (demarcation point)

    A demarc (an abbreviation for demarcation point) marks the point where communications facilities owned by one organization interface with that of another organization.

  • DEN (Directory-Enabled Networking)

    Directory-Enabled Networking (DEN) is an industry-standard initiative and specification for how to construct and store information about a network's users, applications, and data in a central directory.

  • dense wavelength division multiplexing (DWDM)

    Dense wavelength division multiplexing (DWDM) is a technology that puts together -- multiplexes -- data signals from different sources so they can share a single optical fiber pair while maintaining complete separation of the data streams.

  • device relationship management (DRM)

    Device relationship management (DRM) is enterprise software that enables the monitoring, managing, and servicing of intelligent devices over the Internet.

  • DHCP (Dynamic Host Configuration Protocol)

    DHCP (Dynamic Host Configuration Protocol) is a network management protocol used to dynamically assign an Internet Protocol (IP) address to any device, or node, on a network so they can communicate using IP.

  • dial-up

    Dial-up pertains to a telephone connection in a system of many lines shared by many users.

  • Dialed Number Identification Service (DNIS)

    DNIS (Dialed Number Identification Service) is a telephone service that identifies for the receiver of a call the number that the caller dialed.

  • digital loop carrier (DLC)

    DLC also is an abbreviation for Data Link Control.

  • Digital Powerline (DPL)

    Digital Powerline (DPL) technology provides the transmission of data to users over the same lines that bring electric power to homes and businesses.

  • digital switch

    A digital switch is a device that handles digital signals generated at or passed through a telephone company central office and forwards them across the company's backbone network.

  • Direct Access File System (DAFS)

    Direct Access File System (DAFS) is a network file system, similar to Network File System (NFS) and Common Internet File System (CIFS), that allows applications to transfer data while bypassing operating system control, buffering, and network protocol operations that can bottleneck throughput.

  • Direct Outward Dialing (DOD)

    Direct Outward Dialing (DOD) is a service of a local phone company (or local exchange carrier) that allows subscribers within a company's private branch exchange (PBX) system to connect to outside lines directly.

  • direct sequence spread spectrum (DSSS) or direct sequence code division multiple access (DS-CDMA)

    Direct sequence spread spectrum, also known as direct sequence code division multiple access (DS-CDMA), is one of two approaches to spread spectrum modulation for digital signal transmission over the airwaves.

  • discrete multitone (DMT)

    Discrete multitone (DMT) is a method of separating a Digital Subscriber Line (DSL) signal so that the usable frequency range is separated into 256 frequency bands (or channels) of 4.3125 KHz each.

  • disruption-tolerant network (DTN)

    A disruption-tolerant network (DTN) is a network designed so that temporary or intermittent communications problems, limitations and anomalies have the least possible adverse impact... (Continued)

  • Distributed Control Plane Architecture (DCPA)

    A Distributed Control Plane Architecture (DCPA) is a network architecture that makes it possible to allocate control protocol functions across multiple processor levels in the network system.

  • distributed virtual switch

    A distributed virtual switch is an abstract representation of multiple hosts defining the same name, network policy and port group.

  • distributive numerical control (DNC)

    Distributive numerical control (DNC) is a technology that allows a single computer to be networked with one or more machines that use computer numerical control (CNC).

  • DOCSIS (Data Over Cable Service Interface Specifications)

    Now known as CableLabs Certified Cable Modems, DOCSIS (Data Over Cable Service Interface Specifications) is a standard interface for cable modems, the devices that handle incoming and outgoing data signals between a cable TV operator and a personal or business computer or television set.

  • domain name system (DNS)

    The domain name system (DNS) is a naming database in which internet domain names are located and translated into internet protocol (IP) addresses.

  • DoPa (DoCoMo Packet Transmission)

    DoPa (DoCoMo Packet Transmission) is a packet-switched network service developed by NTT DoCoMo in Japan for Internet connection from mobile devices.

  • DOVE (IBM DOVE)

    IBM Dove (Distributed Overlay Virtual Ethernet) is an architecture that allows a network engineer to abstract the physical network infrastructure from hypervisor hosts and make network changes in software rather than hardware.

  • downloading

    Downloading is the transmission of a file from one computer system to another, usually smaller computer system.

  • downstream

    This term should not be confused with downlink.

  • DSLAM (Digital Subscriber Line Access Multiplexer)

    A DSLAM (Digital Subscriber Line Access Multiplexer) is a network device, usually at a telephone company central office, that receives signals from multiple customer Digital Subscriber Line (DSL) connections and puts the signals on a high-speed backbone line using multiplexing techniques.

  • DTE (Data Terminal Equipment)

    In computer data transmission, DTE (Data Terminal Equipment) is the RS-232C interface that a computer uses to exchange data with a modem or other serial device.

  • DTMF (dual tone multi frequency)

    DTMF (dual tone multi frequency) is the signal to the phone company that you generate when you press an ordinary telephone's touch keys.

  • DTTV (digital terrestrial television)

    DTTV (digital terrestrial television, sometimes also abbreviated DTT) is digital television (DTV) broadcast entirely over earthbound circuits.

  • dumb network

    A dumb network is one that provides the physical interconnection between nodes but not much processing to support signaling.

  • duplex

    In telecommunication, duplex communication means that both ends of the communication can send and receive signals at the same time.

  • DVMRP (Distance Vector Multicast Routing Protocol)

    DVMRP (Distance Vector Multicast Routing Protocol) is the oldest routing protocol that has been used to support multicast data transmission over networks.

  • dynamic and static

    In general, dynamic means energetic, capable of action and/or change, or forceful, while static means stationary or fixed.

  • Dynamic ARP Inspection (DAI)

    Dynamic ARP Inspection (DAI) is a security feature that verifies address resolution protocol (ARP) requests and responses in a network.

  • dynamic multipoint VPN (DMVPN)

    A dynamic multipoint virtual private network (DMVPN) is a secure network that exchanges data between sites without needing to pass traffic through an organization's headquarter VPN server or router.

  • dynamic packet filter

    A dynamic packet filter is a firewall facility that can monitor the state of active connections and use this information to determine which network packets to allow through the firewall.

  • dynamic port numbers (private port numbers)

    The dynamic port numbers (also known as the private port numbers) are the port numbers that are available for use by any application to use in communicating with any other application, using the Internet's Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP).

  • Dynamic Source Routing (DSR)

    Dynamic Source Routing (DSR) is a self-maintaining routing protocol for wireless networks. The protocol can also function with cellular telephone systems and mobile networks with up to about 200 nodes. A Dynamic Source Routing network can configure and organize itself independently of oversight by human administrators.

  • dynamic spectrum access (dynamic spectrum management)

    Dynamic spectrum access (DSA), also referred to as dynamic spectrum management (DSM), is a set of spectrum utilization techniques that adjusts frequency in real time based on fluctuating circumstances.

  • E

    E-carrier system

    To see the relationship between the E-carrier system, the T-carrier system, and DS0 multiples, see digital signal X. E1 (or E- is a European digital transmission format devised by the ITU-TS and given the name by the Conference of European Postal and Telecommunication Administration (CEPT).

  • E-ZPass

    E-ZPass is a toll collection system in the northeastern U.S. that uses RFID technology to allow a driver to pass through a tollbooth and pay the toll without stopping the vehicle.

  • E.164

    E.164 is an international numbering plan for public telephone systems in which each assigned number contains a country code (CC), a national destination code (NDC), and a subscriber number (SN).

  • east-west traffic

    East-west traffic, in a networking context, is the transfer of data packets from server to server within a data center. The label east-west comes from network diagram drawings that usually depict local area network (LAN) traffic horizontally.

  • ECC (error correction code or error checking and correcting)

    ECC (either "error correction [or correcting] code" or "error checking and correcting") allows data that is being read or transmitted to be checked for errors and, when necessary, corrected on the fly.

  • edge device

    An edge device is any piece of hardware that controls data flow at the boundary between two networks.

  • edge router

    An edge router is a specialized router located at a network boundary that enables an internal network to connect to external networks.

  • egress

    Egress (pronounced EE-grehs, from Latin egressus, or going out) is the act of going out of something.

  • egress filtering

    Egress filtering is a process in which outbound data is monitored or restricted, usually by means of a firewall that blocks packets that fail to meet certain security requirements.

  • EIGRP (Enhanced Interior Gateway Routing Protocol)

    EIGRP (Enhanced Interior Gateway Routing Protocol) is a network protocol that lets routers exchange information more efficiently than with earlier network protocols.

  • electronic program guide (EPG)

    An electronic program guide (EPG) is an application used with digital set-top boxes and newer television sets to list current and scheduled programs that are or will be available on each channel and a short summary or commentary for each program.

  • ELF (extremely low frequency)

    ELF (extremely low frequency) refers to an electromagnetic field having a frequency much lower than the frequencies of signals typically used in communications.

  • email response management service (ERMS)

    An email response management service (ERMS) is a set of programs that automatically handles email messages and attachments according to user-defined rules... (Continued)

  • Embrane

    Embrane is a company that makes software products for the delivery of SDN (sofware-defined networking) services, including load balancers, firewalls and VPNs.

  • encapsulation

    In general, encapsulation is the inclusion of one thing within another thing so that the included thing is not apparent.

  • encoder

    In digital audio technology, an encoder is a program that converts an audio WAV file into an MP3 file, a highly-compressed sound file that preserves the quality of a CD recording.

  • encoding and decoding

    Encoding is the process of putting a sequence of characters (letters, numbers, punctuation, and certain symbols) into a specialized digital format for efficient transmission or transfer. Decoding is the opposite process -- the conversion of a digital signal into a sequence of characters.

  • enterprise DNS

    Enterprise DNS is an enterprise-class implementation of the domain name system (DNS) that resolves external and internal queries for large organizations in a centrally managed, scalable, automatable and secure way.

  • enterprise WAN

    An enterprise WAN is a corporate network that connects geographically dispersed users areas that could be anywhere in the world.

  • EPOC

    EPOC is an operating system designed for small, portable computer-telephones with wireless access to phone and other information services.

  • erbium amplifier

    An erbium amplifier, also called optical amplifier or an erbium-doped fiber amplifier or EDFA, is an optical or IR repeater that amplifies a modulated laser beam directly, without opto-electronic and electro-optical conversion.

  • erlang

    The Erlang programming language is not the same thing as the erlang, a unit of traffic density.

  • EtherExpress

    EtherExpress is a technology from Intel that is used in network server adapters (devices that attach the server to the network cable) for Ethernet-based local area networks (LANs).

  • EtherLoop

    EtherLoop, sometimes called next generation DSL or second generation DSL, combines features of Digital Subscriber Line (DSL) with features of Ethernet to provide both voice and data transmission (including Internet connection) over any ordinary phone line at data rates faster than DSL. EtherLoop offers a data transfer rate up to 6 Mbps over distances of up to 21,000 feet.

  • Ethernet

    Ethernet is the traditional technology for connecting devices in a wired local area network (LAN) or wide area network (WAN), enabling them to communicate with each other via a protocol -- a set of rules or common network language.

  • Ethernet as a service (EaaS)

    Ethernet as a service (EaaS) is the use of high-bandwidth, fiber optic media such as Packet over SONET (PoS) to deliver 10 Mbps, 100 Mbps or even 1000 Mbps Ethernet service to one or more customers across a common bidirectional broadband infrastructure... (Continued)

  • Ethernet Glossary

    After you've finished, you can test your knowledge with Quiz #28: Ethernet.

  • Ethernet point-of-presence (EPOP)

    Ethernet point-of-presence (EPOP) is a technology developed by Level 3 Communications that provides widespread access to broadband networks. As a large network increases its bandwidth, it can include large and expanding groups of subscribers. This trend, largely the result of the deployment of fiber optic infrastructure, is expected to continue. Thus, wide-area networks (WANs) are taking on some of the characteristics previously unique to local area networks (LANs). The opposite is also true; LANs are becoming increasingly complex, resembling WANs in miniature.

  • ETSI (European Telecommunications Standards Institute)

    The European Telecommunications Standards Institute (ETSI) is a non-profit organization that establishes telecommunications standards for Europe.

  • Evernet

    The term Evernet has been used to describe the convergence of wireless, broadband, and Internet telephony technologies that will result in the ability to be continuously connected to the Web anywhere using virtually any information device.

  • Evolved Packet Core (EPC)

    Evolved Packet Core (EPC) is a flat architecture that provides a converged voice and data networking framework to connect users on a Long-Term Evolutio (LTE) network.

  • extranet

    An extranet is a private network that uses Internet technology and the public telecommunication system to securely share part of a business's information or operations with suppliers, vendors, partners, customers, or other businesses.

  • F

    Fast Ethernet

    Fast Ethernet is a local area network (LAN) transmission standard that provides a data rate of 100 megabits per second (referred to as "100BASE-T").

  • fast retransmit and recovery (FRR)

    In TCP/IP, fast retransmit and recovery (FRR) is a congestion control algorithm that makes it possible to quickly recover lost data packets.

  • fault management

    Fault management is the component of network management concerned with detecting, isolating and resolving problems.

  • fax

    A fax (short for facsimile and sometimes called telecopying) is the telephonic transmission of scanned-in printed material (text or images), usually to a telephone number associated with a printer or other output device.

  • FCAPS (fault-management, configuration, accounting, performance, and security)

    FCAPS is a network management framework created by the International Organization for Standardization (ISO). FCAPS categorizes the working objectives of network management into five levels. The five levels are:  fault-management (F), the configuration level (C), the accounting level (A), the performance level (P) and the security level (S).

  • Fcc

    In Eudora and perhaps other e-mail facilities, you'll see the abbreviations "Fcc" and "Bcc".

  • FDDI (Fiber Distributed Data Interface)

    FDDI (Fiber Distributed Data Interface) is a set of ANSI and ISO standards for data transmission on fiber optic lines in a local area network (LAN) that can extend in range up to 200 km (124 miles).

  • FECN/BECN (forward explicit congestion notification/backward explicit congestion notification)

    In a frame relay network, FECN (forward explicit congestion notification) is a header bit transmitted by the source (sending) terminal requesting that the destination (receiving) terminal slow down its requests for data.

  • Federation of Telecommunications Engineers of the European Community (FITCE)

    FITCE (Federation of Telecommunications Engineers of the European Community) is an international association that is committed to affecting telecommunication developments in a positive and constructive manner throughout Europe and the rest of the world.

  • femtocell

    A femtocell is a wireless access point that improves cellular reception inside a home or office building. The device, which resembles a wireless router, essentially acts as a VOIP repeater.

  • ferrule

    A ferrule (from Latin viriola, meaning little bracelet) is a ring or cap attached to an object to protect against damage, splitting, or wear.

  • FG-D (Feature Group D)

    FG-D (Feature Group D) is a type of telecommunication trunk used to provide "equal access" capability from telecommunication carriers and central offices (where the switching equipment is located and customer lines are connected and terminated) to the access tandem.

  • fiber jumper

    A fiber jumper, sometimes called a fiber patch cord is a length of fiber cabling fitted with LC, SC, MTRJ or ST connectors at each end... (Continued)

  • fiber optics (optical fiber)

    Fiber optics, or optical fiber, refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic strand or fiber.

  • fiber to the curb (FTTC)

    Fiber to the curb (FTTC) refers to the installation and use of optical fiber cable directly to the curbs near homes or any business environment as a replacement for "plain old telephone service" (POTS).

  • fiber to the home (FTTH)

    Fiber to the home (FTTH), also called fiber to the premises (FTTP), is the installation and use of optical fiber from a central point directly to individual buildings such as residences, apartment buildings and businesses to provide unprecedented high-speed Internet access... (Continued)

  • fiber to the x (FTTx)

    Fiber to the x (FTTx) is a collective term for various optical fiber delivery topologies that are categorized according to where the fiber terminates

  • fiberless optics

    Fiberless optics, a term that has been trademarked by Terabeam Networks, is a technology for transmitting large amounts of data on light waves sent through space rather than along an optical fiber cable, thus offering a surprising new solution to the so-called last-mile technology problem.

  • file server

    In the client/server model, a file server is a computer responsible for the central storage and management of data files so that other computers on the same network can access the files.

  • file transfer

    File transfer is the movement of one or more files from one location to another.

  • firehose effect

    A firehose effect occurs in a network when the source (transmitting) computer or terminal sends data too fast for a destination (receiving) computer or terminal to deal with it. The term comes from the analogy between a data stream and the flow of water through the heavy hose used in fighting fire.

  • FireWire

    FireWire is Apple Computer's version of a standard, IEEE 1394, High Performance Serial Bus, for connecting devices to your personal computer.

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