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.

  • F

    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.

  • 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

    In a network, flooding is the forwarding by a router of a packet from any node to every other node attached to the router except the node from which the packet arrived.

  • Floodlight

    Floodlight is a Java-based OpenFlow controller.

  • 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.

  • forest-and-tree model

    The forest-and-tree model is a logical structure for interconnecting multiple network domains in Windows 2000 and later operating systems.

  • forklift upgrade

    Forklift upgrade is industry slang for replacing or significantly upgrading an IT infrastructure. IT transformation is a more formal way to describe the same concept.

  • Forward DNS lookup

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

  • four-way server

    A four-way server is a server that incorporates a multi-core processor for increased performance... (Continued)

  • fractional T1

    A fractional T1 or T3 line is a T1 or T3 digital phone line in the North American T-carrier system that is leased to a customer at a fraction of its data-carrying capacity and at a correspondingly lower cost.

  • FRAD (frame relay access device or frame relay assembler/dissembler)

    A FRAD (frame relay access device; also sometimes referred to as a frame relay assembler/dissembler) is a box that encapsulates (puts frame relay header and trailer information on) outgoing data packets and decapsulates (removes frame relay headers and trailers from) incoming packets.

  • frame

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

  • frame rate

    In motion pictures, television, and in computer video displays, the frame rate is the number of frames or images that are projected or displayed per second.

  • Freephone

    In the U.K., Freephone is a type of Number Translation Service (NTS) that allows a phone user to call a non-geographic number beginning with 0800 or 0500 without incurring a charge.

  • frequency modulation (FM)

    Also see modulation and frequency-shift keying (FSK).

  • frequency-division multiplexing (FDM)

    Frequency-division multiplexing (FDM) is a scheme in which numerous signals are combined for transmission on a single communications line or channel.

  • frequency-hopping spread spectrum

    Frequency hopping is one of two basic modulation techniques used in spread spectrum signal transmission.

  • frequency-shift keying (FSK)

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

  • FTAM (File Transfer Access Method)

    File Transfer Access Method (FTAM), also known as File Transfer Access and Management or Electronic File Transfer Access Method (EFTAM), is an ISO standard that specifies methods of transfering files between networked computers... (Continued)

  • FTP (File Transfer Protocol)

    File Transfer Protocol (FTP) is a client-server standard used to transfer files between computers over the Internet using control and data channels.

  • FTP cable (foil screened twisted pair cable)

    FTP (foil screened twisted pair) cable is a cable containing multiple pairs of copper wire enclosed in a sheath of aluminum foil.

  • full-duplex

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

  • G

    G.703

    G.703 is a CCITT standard for transmitting voice over digital carriers such as T1 and E1. G.703 provides the specifications for pulse code modulation (PCM) at data rates from 64 Kbps to 2.048 Mbps.

  • 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

    In data communications, a gigabit is one billion bits, or 1,000,000,000 (that is, 10^9) bits. It's commonly used for measuring the amount of data that is transferred in a second between two telecommunication points.

  • Gigabit Ethernet

    Gigabit Ethernet, 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 (one gigabit). (Continued...)

  • gigahertz (GHz)

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

  • 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.

  • GLONASS (Globalnaya Navigatsionnay Sputnikovaya Sistema)

    GLONASS (for Globalnaya Navigatsionnay Sputnikovaya Sistema), the Russian Federation's Global Navigation Satellite System (GNSS), is the Russian version of a global positioning system.

  • 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.

  • green route

    A green route is one of three categories of Internet route states defined by the Policy Analysis of Internet Routing (PAIR) project, an initiative dedicated to the development of tools that ISPs (Internet service providers), network operators, and end users can use to troubleshoot Internet routing and policy problems.

  • grey route

    A grey route is one of three categories of Internet routes defined by the Policy Analysis of Internet Routing (PAIR) project, an initiative dedicated to the development of tools that ISPs (Internet service providers), network operators, and end users can use to troubleshoot Internet routing and policy problems.

  • 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 protocol that facilitates control of virtual local area networks (VLANs) within a larger network . GVRP conforms to the IEEE 802.1Q specification, which defines a method of tagging frames with VLAN configuration data.

  • H

    H.323

    H.323 is a standard approved by the International Telecommunication Union (ITU) in 1996 to promote compatibility in videoconference transmissions over IP networks.

  • 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.

  • handshaking

    In telephone communication, handshaking is the exchange of information between two modems and the resulting agreement about which protocol to use that precedes each telephone connection.

  • 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.

  • hardware VPN

    A hardware VPN is a virtual private network ( VPN) based on a single, stand-alone device.

  • Hayes command set

    Hayes command set is a specific programming language originally developed for the Hayes Smartmodem 300 baud modem during the late 1970s... (Continued)

  • 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).

  • HDSL (High bit-rate Digital Subscriber Line)

    Also see our Fast guide to DSL. HDSL (High bit-rate Digital Subscriber Line), one of the earliest forms of DSL, is used for wideband digital transmission within a corporate site and between the telephone company and a customer.

  • 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.

  • High-Speed Circuit-Switched Data (HSCSD)

    High-Speed Circuit-Switched Data (HSCSD) is circuit-switched wireless data transmission for mobile users at data rates up to 38.4 Kbps, four times faster than the standard data rates of the Global System for Mobile (GSM) communication standard in 1999. HSCSD is comparable to the speed of many computer modems that communicate with today's fixed telephone networks.

  • high-speed dialup

    High-speed dialup, sometimes advertised as broadband dialup, is an Internet service provider (ISP) feature that speeds up data transfer by using a special server, called an acceleration server, to act as a bridge between the user's dialup connection and a Web page.

  • High-Speed Serial Interface (HSSI)

    High-Speed Serial Interface (HSSI) is a short-distance communications interface that is commonly used to interconnect routing and switching devices on local area networks (LANs) with the higher-speed lines of a wide area network (WAN).

  • home address

    In the Mobile Internet Protocol (Mobile IP), a home address is the relatively permanent IP address given to a mobile node.

  • 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 network

    Using Mobile IP (Mobile Internet Protocol), the home network is where a mobile device has its permanent IP address.

  • 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.

  • home server

    A home server is a computer that functions as a server in a client-server home network.

  • HomeRF (home radio frequency)

    HomeRF (for home radio frequency) is a home networking standard developed by Proxim Inc.

  • hoot-n-holler

    In telecommunications, a hoot-n-holler is a dedicated "always on" connection used for two-way business-to-business voice communication.

  • host (in computing)

    A host (also known as "network host") is a computer or other device that communicates with other hosts on a network.

  • Hot Standby Router Protocol (HSRP)

    Hot Standby Router Protocol (HSRP) is a routing protocol that allows host computers on the Internet to use multiple routers that act as a single virtual router, maintaining connectivity even if the first hop router fails, because other routers are on "hot standby" - ready to go.

  • How do I...choose a VPN for my small business?

    A virtual private network (VPN)is a way to use a public telecommunication infrastructure, such as the Internet,to provide remote offices or individual users with secure access to their organization's network.

  • htaccess

    .htaccess is the default name for a file that is used to indicate who can or cannot access the contents of a specific file directory from the Internet or an intranet.

  • HTTP/2 protocol

    HTTP/2 protocol is the second version of HTTP, a network protocol used to define the format and transmission of data.

  • hybrid fiber coaxial network (HFC network)

    A hybrid fiber coaxial (HFC) network is a telecommunication technology in which optical fiber cable and coaxial cable are used in different portions of a network to carry broadband content (such as video, data, and voice).

  • hybrid SDN

    A hybrid SDN (software-defined network) is a network where both traditional networking and SDN protocols operate in the same environment.

  • hybrid WAN

    A hybrid WAN is a wide area network that sends traffic over two or more connection types. Hybrid WANs permit dynamic traffic engineering across both private and public domains, using a variety of connectivity options to make the best use of network resources.

  • network hub

    A network hub is a node that broadcasts data to every computer or Ethernet-based device connected to it.

  • I

    i-Mode

    i-Mode is the packet-based service for mobile phones offered by Japan's leader in wireless technology, NTT DoCoMo.

  • ICMP (Internet Control Message Protocol)

    ICMP (Internet Control Message Protocol) is an error-reporting and message-control protocol that network devices use to report problems in IP packet delivery.

  • iDEN (Integrated Digital Enhanced Network)

    iDEN (Integrated Digital Enhanced Network) is a wireless technology from Motorola combining the capabilities of a digital cellular telephone, two-way radio, alphanumeric pager and data/fax modem in a single network.

  • IDSL

    IDSL is a system in which digital data is transmitted at 128 Kbps on a regular copper telephone line (twisted pair) from a user to a destination using digital (rather than analog or voice) transmission, bypassing the telephone company's central office equipment that handles analog signals.

  • IEEE 802 wireless standards

    The IEEE 802 standard is a collection of networking standards that cover the physical and data-link layer specifications for technologies such as Ethernet and wireless.

  • in-band signaling

    In the public switched telephone network, (PSTN), in-band signaling is the exchange of signaling (call control) information on the same channel that the telephone call itself is using.

  • iNet

    An iNet (pronounced AI-neht) is any network that uses the Internet Protocol (IP).

  • information theory

    Information theory is a branch of mathematics that overlaps into communications engineering, biology, medical science, sociology, and psychology.

  • infranet

    The infranet is a proposed universal, public, packet-switched supplement to the Internet for businesses and high-demand private users that would provide guaranteed security, reliability, and quality of service (QoS).

  • Infranet Initiative

    The Infranet Initiative is a collaborative effort to develop a high-performance universal public network that would serve as a supplement to the Internet for businesses and other high-demand users.

  • infrared radiation (IR)

    Infrared radiation (IR), sometimes referred to simply as infrared, is a region of the electromagnetic radiation spectrum where wavelengths range from about 700 nanometers (nm) to 1 millimeter (mm).

  • infrared transmission

    Infrared transmission refers to energy in the region of the electromagnetic radiation spectrum at wavelength s longer than those of visible light, but shorter than those of radio

  • ingress filtering

    Ingress filtering is a method used by enterprises and internet service providers (ISPs) to prevent suspicious traffic from entering a network.

  • integrated T1 (channelized T1)

    Integrated T1 (also called channelized T is a digital carrier modulation method in which a T1 line is divided into 24 channels, each having a maximum data speed of 64 thousand bits per second (Kbps), and each capable of supporting a unique application that can run concurrently with, but independently of, other applications on different channels.

  • Intelligent Network (IN)

    Intelligent Network (IN) is a telephone network architecture originated by Bell Communications Research (Bellcore) in which the service logic for a call is located separately from the switching facilities, allowing services to be added or changed without having to redesign switching equipment.

  • Internet Group Management Protocol (IGMP)

    The Internet Group Management Protocol (IGMP) is an Internet protocol that provides a way for an Internet computer to report its multicast group membership to adjacent routers.

  • Internet metering

    Internet metering is a service model in which an Internet service provider (ISP) tracks the customer's use of bandwidth and charges accordingly. Typically, the customer selects a service package with a flat rate up to a specified limit and pays, probably per gigabyte, beyond that limit... (Continued)

  • Internet Routing in Space (IRIS)

    Internet Routing in Space in Space, also known as (IRIS), is a project being conducted by the U.S. Department of Defense to place an IP (Internet protocol) router on a geostationary satellite... (Continued)

  • internetworking

    Internetworking is a term used by Cisco, BBN, and other providers of network products and services as a comprehensive term for all the concepts, technologies, and generic devices that allow people and their computers to communicate across different kinds of networks.

  • inverse multiplexing over ATM (IMA)

    Inverse multiplexing over ATM (IMA) is a method of optimizing the data transfer rate for individual subscribers in networks that use asynchronous transfer mode (ATM) by dividing the data into multiple concurrent streams that are sent across separate channels and reconstructed at the destination, obtaining the original data stream... (Continued)

  • IP Multimedia Subsystem (IMS)

    The IP Multimedia Subsystem (IMS) is a concept for an integrated network of telecommunications carriers that would facilitate the use of IP (Internet Protocol) for packet communications in all known forms over wireless or landline... (Continued)

  • IPLC (international private leased circuit)

    An IPLC (international private leased circuit) is a point-to-point private line used by an organization to communicate between offices that are geographically dispersed throughout the world.

  • IPTV (Internet Protocol television)

    IPTV (Internet Protocol television) is a service that provides television programming and other video content using the TCP/IP protocol suite as opposed to traditional cable or satellite signals.

  • IPv6 (Internet Protocol Version 6)

    IPv6 is a set of specifications from the Internet Engineering Task Force that improves IPv4 by extending IP addresses from 32 bits to 128 bits.

  • IPX (Internetwork Packet Exchange)

    IPX (Internetwork Packet Exchange) is a networking protocol from Novell that interconnects networks that use Novell's NetWare clients and servers.

  • IS-IS (Intermediate System-to-Intermediate System protocol)

    One of the most commonly used routing protocols, the Intermediate System-to-Intermediate System protocol (IS-IS) is based on a routing method known as DECnet Phase V routing, in which routers known as intermediate systems exchange data about routing using a single metric to determine the network topology.

  • ISDN (Integrated Services Digital Network)

    ISDN (Integrated Services Digital Network) is a set of CCITT/ITU standards for digital transmission over ordinary telephone copper wire, as well as over other media.

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