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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  • C

    CSU/DSU (Channel Service Unit/Data Service Unit)

    A CSU/DSU (Channel Service Unit/Data Service Unit) is a hardware device about the size of an external modem that converts a digital data frame from the communications technology used on a local area network (LAN) into a frame appropriate to a wide-area network (WAN) and vice versa.

  • customer premises equipment (CPE)

    Customer premises equipment (CPE) is telecommunications and information technology equipment kept at the customer's physical location rather than on the service provider's premises.

  • customer proprietary network information (CPNI)

    Customer proprietary network information (CPNI) in the United States is information that telecommunications services -- such as local, long-distance and wireless telephone companies -- acquire about their subscribers.

  • cyclic redundancy checking

    Cyclic redundancy checking is a method of checking for errors in data that has been transmitted on a communications link.

  • D

    D-channel

    In the Integrated Services Digital Network (ISDN), the D-channel is the channel that carries control and signalling information.

  • data center interconnect (DCI)

    Data center interconnect (DCI) is a segment of the networking market that focuses on the technology used to link two or more data centers so the facilities can share resources. There are many options for DCI connectivity and selecting the right one depends upon a wide range of variables, including the location of the data centers, the distance between data centers, bandwidth and availability requirements, the capabilities of local service providers and security concerns.

  • data link control (DLC)

    DLC also is an abbreviation for digital loop carrier.

  • 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.

  • 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.

  • dense wavelength-division multiplexing (DWDM)

    Dense wavelength-division multiplexing (DWDM) is an optical fiber multiplexing technology that is used to increase the bandwidth of existing fiber networks.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • downloading

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

  • 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.

  • DTMF (dual tone multi-frequency)

    Dual tone multi-frequency (DTMF) is the sounds or tones generated by a telephone when the numbers are pressed.

  • duplex

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

  • 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 port numbers

    Dynamic port numbers, also known as 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 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.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.

  • 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.

  • encapsulation

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

  • encoding and decoding

    Encoding and decoding are used in many forms of communications, including computing, data communications, programming, digital electronics and human communications.

  • Enhanced Interior Gateway Routing Protocol (EIGRP)

    Enhanced Interior Gateway Routing Protocol (EIGRP) is a network protocol that enables routers to exchange information more efficiently than earlier network protocols, such as Interior Gateway Routing Protocol (IGRP) or Border Gateway Protocol (BGP).

  • 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.

  • 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).

  • 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 Glossary

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

  • 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 enterprises use to provide trusted third parties -- such as suppliers, vendors, partners, customers and other businesses -- secure, controlled access to business information or operations.

  • F

    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, configuration, accounting, performance and security)

    FCAPS (fault, configuration, accounting, performance and security) is a network management framework created by the International Organization for Standardization (ISO).

  • FDDI (Fiber Distributed Data Interface)

    FDDI (Fiber Distributed Data Interface) is a network standard that uses fiber optic connections in a local area network (LAN) that can extend in range up to 200 kilometers (124 miles).

  • 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 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 high-speed internet access.

  • 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

  • file server

    A file server is a computer responsible for the storage and management of data files so that other computers on the same network can access the files.

  • File Transfer Access and Management (FTAM)

    File Transfer Access and Management (FTAM) is an OSI application Layer 7 protocol that standardizes how files are accessed and managed in a distributed network file system.

  • firewall as a service (FWaaS)

    Firewall as a service (FWaaS), also known as a cloud firewall, is a service that provides cloud-based network traffic inspection capabilities to customers seeking to decommission or augment their existing network firewall appliances.

  • FireWire

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

  • fixed-length subnet mask (FLSM)

    A fixed-length subnet mask (FLSM) is a sequence of numbers of unchanging length that streamlines packet routing within the subnets of a proprietary network... (Continued)

  • flooding (network)

    In a computer network, flooding occurs when a router uses a non-adaptive routing algorithm to send an incoming packet to every outgoing link except the node on which the packet arrived.

  • flow routing

    Flow routing is a network routing technology that takes variations in the flow of data into account to increase routing efficiency... (Continued)

  • FlowVisor

    FlowVisor is an experimental software-defined networking controller that enables network virtualization by slicing a physical network into multiple logical networks.

  • foreign agent

    In Mobile Internet Protocol (Mobile IP), a foreign agent is a router serving as a mobility agent for a mobile node.

  • foreign network

    In the Mobile Internet Protocol (Mobile IP), a foreign network is any network other than the home network to which a mobile device may be connected.

  • Forward DNS lookup

    Forward DNS lookup is using an Internet domain name to find an IP address.

  • frame

    See frames for the use of multiple Web pages on a single display screen.

  • frame relay

    Frame relay is a packet-switching telecommunications service designed for cost-efficient data transmission for intermittent traffic between local area networks (LANs) and between endpoints in wide area networks (WANs).

  • frequency-division multiplexing (FDM)

    In frequency-division multiplexing (FDM), multiple signals are combined for transmission on a single communications line or channel, with each signal assigned to a different frequency (subchannel) within the main channel.

  • frequency-hopping spread spectrum (FHSS)

    Frequency-hopping spread spectrum (FHSS) transmission is the repeated switching of the carrier frequency during radio transmission to reduce interference and avoid interception.

  • frequency-shift keying (FSK)

    Frequency-shift keying (FSK) is a method of transmitting digital signals.

  • FTP (File Transfer Protocol)

    FTP (File Transfer Protocol) is a network protocol for transmitting files between computers over TCP/IP connections.

  • full-duplex

    Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time.

  • G

    GARP (Generic Attribute Registration Protocol)

    GARP (Generic Attribute Registration Protocol) is a local area network (LAN) protocol that defines procedures by which end stations and switches can register and de-register attributes, such as network identifiers or addresses, with each other...

  • Generic Routing Encapsulation (GRE)

    Generic Routing Encapsulation (GRE) is a simple protocol that encapsulates packets in order to route other protocols over IP networks, as defined by RFC 2784.

  • Gigabit Ethernet (GbE)

    Gigabit Ethernet (GbE), a transmission technology based on the Ethernet frame format and protocol used in local area networks (LANs), provides a data rate of 1 billion bits per second, or 1 gigabit (Gb).

  • gigapop (gigabit point-of-presence)

    Gigapop is short for gigabit point-of-presence, an access point to Internet2, the network collaboration between universities and partners in industry and government to develop advanced Internet technologies and applications such as telemedicine and digital libraries.

  • GMPLS (Generalized Multiprotocol Label Switching or Multiprotocol Lambda Switching)

    GMPLS (Generalized Multiprotocol Label Switching), also known as Multiprotocol Lambda Switching, is a technology that provides enhancements to Multiprotocol Label Switching (MPLS) to support network switching for time, wavelength, and space switching as well as for packet switching.

  • GNSS (Global Navigation Satellite System)

    GNSS (Global Navigation Satellite System) is a satellite system that is used to pinpoint the geographic location of a user's receiver anywhere in the world.

  • graceful degradation

    Graceful degradation is the ability of a computer, machine, electronic system or network to maintain limited functionality even when a large portion of it has been destroyed or rendered inoperative. The purpose of graceful degradation is to prevent catastrophic failure... (Continued)

  • green networking

    Green networking is the practice of selecting energy-efficient networking technologies and products, and minimizing resource use whenever possible.

  • GTAG (Global Tag)

    GTAG (Global Tag) is a standardization initiative of the Uniform Code Council (UCC) and the European Article Numbering Association (EAN) for asset tracking and logistics based on radio frequency identification (RFID).

  • GVRP (GARP VLAN Registration Protocol or Generic VLAN Registration Protocol)

    GVRP (GARP VLAN Registration Protocol or Generic VLAN Registration Protocol) is a standards-based protocol that facilitates control of virtual local area networks (VLANs) within a larger network.

  • H

    half-duplex

    Half-duplex data transmission means that data can be transmitted in both directions on a signal carrier, but not at the same time.

  • HAProxy

    HAProxy (High Availability Proxy), developed by HAProxy Technologies LLC, is an open source load balancer proxy for TCP and HTTP applications.

  • hardware load-balancing device (HLD)

    A hardware load-balancing device (HLD), also known as a layer 4-7 router, is a physical unit that directs computers to individual servers in a network, based on factors such as server processor utilization, the number of connections to a server, or the overall server performance.

  • HDLC (High-level Data Link Control)

    HDLC (High-level Data Link Control) is a group of protocols or rules for transmitting data between network points (sometimes called nodes).

  • HELLO packet

    In the Open Shortest Path First (OSPF) communications protocol - which enables network routers to share information with each other, a HELLO packet is a special packet (message) that is sent out periodically from a router to establish and confirm network adjacency relationships.

  • home agent

    In Mobile Internet Protocol (Mobile IP), a home agent is a router on a mobile node's home network that maintains information about the device's current location, as identified in its care-of address.

  • Home Location Register (HLR)

    The Home Location Register (HLR) is the main database of permanent subscriber information for a mobile network.

  • Home Phoneline Networking Alliance (HPNA)

    The HPNA (Home Phoneline Networking Alliance) is an industry group that promotes standards for using existing phone lines and jacks to interconnect computers within a home.

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