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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  • T

    terminal adapter (TA)

    A terminal adapter (TA) is a hardware interface between a computer and an Integrated Services Digital Network line.

  • terminal emulation

    Terminal emulation is the ability to make one computer terminal, typically a PC, appear to look like another, usually older type of terminal so that a user can access programs originally written to communicate with the other terminal type.

  • terminal proxy server (TPS)

    A terminal proxy server (TPS) is a program that acts as an interface for voice over Internet Protocol (VoIP) telephone sets... (Continued)

  • ternary content-addressable memory (TCAM)

    Ternary content-addressable memory (TCAM) is a specialized type of high-speed memory that searches its entire contents in a single clock cycle, with the term “ternary” referring to its ability to store and query data using three different inputs: 0, 1 and X.

  • text on nine keys (T9)

    Text on nine keys (T9) is a system that lets fixed and mobile phone users send text messages by pressing a number key for each letter in the message -- effectively making a keyboard out of the nine numeric phone entry keys.

  • thermoelectric cooling

    Thermoelectric cooling is a way to remove thermal energy from a medium, device or component by applying a voltage of constant polarity to a junction between dissimilar electrical conductors or semiconductors...(continued)

  • thin client (lean client)

    A thin client, sometimes called a lean client, is a low-cost, centrally-managed computer that relies heavily on a server for its computational role.

  • Thinnet

    Thicknet and Thinnet (sometimes called ThickWire and ThinWire) are commonly used terms for the larger and smaller size of coaxial cable used in Ethernet local area networks.

  • throttled data transfer

    Throttled data transfer, also known as data transfer throttling or lean data transfer, is the deliberate regulation of the data transfer rate in a communications system... (Continued)

  • throughput

    Throughput is a term used in information technology that indicates how many units of information can be processed in a set amount of time.

  • time-to-live (TTL)

    Time-to-live (TTL) is a value in an Internet Protocol (IP) packet that tells a network router whether or not the packet has been in the network too long and should be discarded.

  • token ring

    A token ring network connects computers in a ring or star topology to prevent the collision of data between two computers sending messages simultaneously.

  • top-of-rack switching

    Top-of-rack switching refers to a distributed data center architecture where one or more Ethernet switches is installed in a rack, then uplinked using high-bandwidth fiber optic connections to a central, high-density distribution point.

  • Toslink

    Toslink is a connector format for fiber optic digital audio cables.

  • TP0-TP4 (transport protocols 0 to 4)

    TP0-TP4 (transport protocols 0 to 4) are the five protocols in the Transport layer of the Open Systems Interconnection (OSI) model for telecommunication.

  • traffic engineering

    Traffic engineering is a method of optimizing the performance of a telecommunications network by dynamically analyzing, predicting and regulating the behavior of data transmitted over that network... (Continued)

  • traffic shaping

    Traffic shaping, also known as packet shaping, is a congestion management method that regulates network data transfer by delaying the flow of less important or less desired packets.

  • transactional e-mail

    Transactional e-mail is a type of Web-based marketing in which e-mail recipients can buy goods and services directly from an e-mail message, without being redirected to the retailer's Web site.

  • transceiver

    A transceiver is a combination transmitter/receiver in a single package.

  • transit

    Transit is the connection to and use of a telecommunication path provided by a vendor.

  • Transmeta

    Transmeta is a Silicon Valley start-up company known for its recruitment of high profile talent and its Crusoe chip, designed for mobile Internet computing.

  • transparent addressing

    On a wide area network (WAN), transparent addressing is a method of network addressing in which all intermediate node addresses are spoofed, so the client and server see each other's addresses and port configurations as if there were no intermediate nodes.

  • Transparent Interconnection of Lots of Links (TRILL)

    Transparent Interconnection of Lots of Links (TRILL) is the Internet Engineering Task Force’s specification for enabling multi-pathing in the data center. The protocol is intended to replace the spanning tree protocol.

  • transport layer

    Positioned at Layer 4 of the Open Systems Interconnection (OSI) communications model, the transport layer ensures the reliable arrival of messages across a network and provides error-checking mechanisms and data flow controls.

  • Transport Services Access Point (TSAP)

    A Transport Services Access Point (TSAP) is an end-point for communication between the Transport layer (layer 4) and the Session layer in the OSI (Open Systems Interconnection) reference model.

  • Traversal Using Relay NAT (TURN)

    Traversal Using Relay NAT (TURN) is a protocol, currently at the working draft stage, that is intended to govern the reception of data over a Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) connection by a single communications device operating behind a Network Address Translator (NAT) or firewall... (Continued)

  • tree network

    In telecommunication networks, a tree network is a combination of two or more star networks connected together.

  • Trema

    Trema is an open source framework for developing OpenFlow controllers for software-defined networking in the Ruby and C programming languages.

  • triangulation

    Triangulation is a process by which the location of a radio transmitter can be determined by measuring either the radial distance, or the direction, of the received signal from two or three different points.

  • triple-play network

    A triple-play network is one in which voice, video and data are all provided in a single access subscription... (Continued)

  • triplecast

    A triplecast (TM) is the simultaneous broadcast of a program on television, radio, and an Internet site or channel.

  • tru2way

    Tru2way is the trade name for a technology that facilitates interactive TV and the convergence of digital television (DTV) with other communications devices... (Continued)

  • trunk

    A trunk is a physical path or link in a communications system that interconnects major switching centers or nodes and is designed to handle many transmissions simultaneously.

  • Turtle Firewall

    Turtle Firewall is an open source firewall program written in Perl that supports Linux Kernels 2.4.x and iptables. Turtle Firewall was written by Andrea Frigido of Frisoft, and is available under the GNU Public License (GPL) .

  • twinaxial cable

    Twinaxial cable is coaxial cable that contains two inner conducting wires rather than one.

  • two-tiered Internet

    Two-tiered Internet refers to proposed changes in Internet architecture that would give priority to the traffic of those who have paid for premium service.

  • two-way server

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

  • U

    U interface

    In Integrated Services Digital Network (ISDN) Basic Rate Interface service, a U interface is the electrical interface for the single twisted pair wire connection from a local phone company (the central office) to a home or business.

  • UDP (User Datagram Protocol)

    UDP (User Datagram Protocol) is a communications protocol that is primarily used for establishing low-latency and loss-tolerating connections between applications on the internet.

  • UHF (ultrahigh frequency)

    The UHF (ultrahigh frequency) range of the radio spectrum is the band extending from 300 MHz to 3 GHz.

  • Undernet

    For terms frequently used in online keyboard chatting, see chat acronyms/IRC/BBS. According to its home page, the Undernet is the largest network of Internet Relay Channels (IRC) on the Internet.

  • unicast

    Unicast is communication between a single sender and a single receiver over a network.

  • universal network

    The "universal network" is the idea of a single network that integrates the existing voice and public telecommunications network (including the Internet), cable TV, data networks, and video broadcast networks so that they work together well.

  • Unshielded Twisted Pair (UTP)

    Unshielded twisted pair (UTP) is a ubiquitous type of copper cabling used in telephone wiring and local area networks (LANs).

  • URL (Uniform Resource Locator)

    A URL (Uniform Resource Locator) is a unique identifier used to locate a resource on the internet. It is also referred to as a web address.

  • Usenet

    Usenet is a collection of user-submitted notes or messages on various subjects that are posted to servers on a worldwide network.

  • USSD (Unstructured Supplementary Service Data)

    USSD (Unstructured Supplementary Service Data) is a GSM (Global System for Mobile) communications protocol that is used to send text messages.

  • UUCP (UNIX-to-UNIX Copy Protocol)

    UUCP (UNIX-to-UNIX Copy Protocol) is a set of UNIX programs for copying (sending) files between different UNIX systems and for sending commands to be executed on another system.

  • Uuencode (Uuencode/Uudecode)

    Uuencode (also called Uuencode/Uudecode) is a popular utility for encoding and decoding files exchanged between users or systems in a network.

  • V

    V.90

    V.90 is a A Tour of the Internet, Who Runs It, Standards Org, approved by the International Telecommunications Union (ITU-TS), for transmitting data downstream to modems at 56 Kbps (thousand bits per second).

  • V.xx

    The V Series Recommendations from the ITU-TS are summarized in the table below.

  • value-added network (VAN)

    A value-added network (VAN) is a private network provider (sometimes called a turnkey communications line) that is hired by a company to facilitate electronic data interchange (EDI) or provide other network services.

  • vampire tap

    A vampire tap is a connection to a coaxial cable in which a hole is drilled through the outer shield of the cable so that a clamp can be connected to the inner conductor of the cable.

  • variable-length subnet mask (VLSM)

    Definition: Learn what a variable-length subnet mask (VLSM) is and how it allows network engineers to reduce the number of wasted IP addresses in each subnet.

  • varicode

    Varicode is a method of binary character encoding in which the number of bits for each character is not fixed, but varies for each character depending on how often that character occurs in general usage.

  • vBNS (very high-speed Backbone Network Service)

    The vBNS (very high-speed Backbone Network Service) is a network that interconnects a number of supercomputer centers in the United States and is reserved for science applications requiring the massive computing that supercomputers can provide.

  • vCPE (virtual customer premises equipment)

    Virtual customer premises equipment (also referred to as vCPE or cloud CPE) are enterprise network services delivered through software. While providers must manually deploy traditional, physical CPE devices onsite, they can provision and manage vCPE remotely.

  • vEPC (virtual Evolved Packet Core)

    The vEPC offers a framework to support converged voice and data on 4G Long-Term Evolution networks. vEPC is the abstraction of Evolved Packet Core components into software that runs on generic servers, potentially cutting costs and improving service delivery.

  • Veronica

    Veronica is a program that allowed you to search the files of the Internet's Gopher servers for a particular search string.

  • VHF (very high frequency)

    The VHF (very high frequency) range of the radio spectrum is the band extending from 30 MHz to 300 MHz.

  • video on demand (VoD)

    Video on demand (VoD) is an interactive TV technology that allows subscribers to view programming in real time or download programs and view them later... (Continued)

  • virtual area network (VAN)

    A virtual area network (VAN) is a network on which users are enabled to share a more visual sense of community through high band-width connections.

  • virtual circuit

    A virtual circuit is a circuit or path between points in a network that appears to be a discrete, physical path but is actually a managed pool of circuit resources from which specific circuits are allocated as needed to meet traffic requirements.

  • virtual network adapter

    A virtual network adapter is a program (instead of a physical network adapter) that allows a computer to connect to a network. A virtual network adapter can also be used to connect all the computers on a local area network (LAN) to a larger network such as the Internet or a collection of LANs.

  • virtual network computing (VNC)

    Virtual network computing (VNC) is a type of remote-control software that makes it possible to control another computer over a network connection...

  • virtual network functions (VNF)

    Virtual network functions (VNFs) are virtualized tasks formerly carried out by proprietary, dedicated hardware. VNFs move individual network functions out of dedicated hardware devices into software that runs on commodity hardware.

  • virtual private LAN service (VPLS)

    Virtual private LAN service (VPLS) is a technology that makes it possible to connect geographically dispersed local area networks (LANs) logically over the Internet.

  • virtual server

    On the Internet, a virtual server is a server (computer and various server programs) at someone else's location that is shared by multiple Web site owners so that each owner can use and administer it as though they had complete control of the server.

  • virtual systems management (VSM)

    Virtual systems management (VSM), also known as virtual system management, is the process of remotely managing the allocation and use of resources in conventional networks as well as in virtual area networks (VANs), virtual private networks (VPNs), virtual network computing (VNC) and virtual servers... (Continued)

  • visitor-based networking (VBN)

    Visitor-based networking (VBN) is the provision of high-speed Internet access for mobile PC users in need of temporary service in public places.

  • VLAN (virtual LAN)

    A VLAN (virtual LAN) is a subnetwork which can group together collections of devices on separate physical local area networks (LANs).

  • voice over LTE (VoLTE)

    Voice over LTE (VoLTE) is a digital packet technology that uses 4G LTE networks to route voice traffic and transmit data.

  • VPN (virtual private network)

    A virtual private network (VPN) is programming that creates a safe, encrypted connection over a less secure network, such as the public internet. A VPN uses tunneling protocols to encrypt data at the sending end and decrypt it at the receiving end.

  • VPN appliance

    A VPN (virtual private network) appliance is a network device equipped with enhanced security features... (Continued)

  • VRRP (Virtual Router Redundancy Protocol)

    VRRP (Virtual Router Redundancy Protocol) is an Internet protocol that provides a way to have one or more backup routers when using a statically configured router on a local area network (LAN).

  • VTAM (Virtual Telecommunications Access Method)

    VTAM (Virtual Telecommunications Access Method) is an IBM application program interface (API) for communicating with telecommunication devices and their users.

  • VXLAN gateway (Virtual Extensible VLAN gateway)

    A VXLAN gateway is a solution that allows a virtual extensible LAN (VXLAN) to communicate with another network, particularly a virtual LAN (VLAN).

  • VxWorks

    VxWorks is a real-time operating system (RTOS) that can be used in embedded systems... (Continued)

  • W

    Wake on LAN

    Wake on LAN is a technology that allows a network professional to remotely power on a computer or to wake it up from sleep mode.

  • WAN (Wide Area Network)

    A wide area network (WAN) is a geographically distributed telecommunications network that interconnects multiple local area networks (LANs).

  • WAN accelerator

    A WAN accelerator is an appliance that improves the end user's experience on a wide area network (WAN).

  • WAN clustering (geoclustering, high-availability clustering or remote clustering)

    WAN clustering, also called geoclustering, high-availability clustering or remote clustering, is the use of multiple redundant computing resources located in different geographical locations to form what appears to be a single highly-available system.

  • WAN interface card (WIC)

    A WAN interface card, or WIC, is a specialized network interface card (NIC) that allows devices to connect to a wide area network.

  • WAN optimization (WAN acceleration)

    WAN optimization -- also known as WAN acceleration -- is the category of technologies and techniques used to maximize the efficiency of data's flow across a wide area network (WAN), between organizations' centralized data centers and their remote locations.

  • WATS (wide-area telephone service)

    WATS (wide-area telephone service) is a specialized form of fixed-rate long-distance telecommunication service.

  • wavelength

    Wavelength is the distance between identical points (adjacent crests) in the adjacent cycles of a waveform signal propagated in space or along a wire.

  • wavelength-division multiplexing (WDM)

    Wavelength-division multiplexing (WDM) is a method of combining multiple signals on laser beams at various infared (IR) wavelengths for transmission along fiber optic media. Each laser is modulated by an independent set of signals. Wavelength-sensitive filters, the IR analog of visible-light color filters, are used at the receiving end... (Continued...)

  • Webcast

    Also see push technology, another usage.

  • WebNFS

    WebNFS is a product and proposed standard protocol from Sun Microsystems that extends its Network File System (NFS) to the Internet.

  • weighted fair queueing (WFQ)

    Weighted fair queueing (WFQ) is a method of automatically smoothing out the flow of data in packet-switched communication networks by sorting packets to minimize the average latency and prevent exaggerated discrepancies between the transmission efficiency afforded to narrowband versus broadband signals.

  • well-known port numbers

    The well-known port numbers are the port numbers that are reserved for assignment by the Internet Corporation for Assigned Names and Numbers (ICANN) for use by the application end points that communicate using the Internet's Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP).

  • white box switch

    A white box switch is built on a low-cost, bare metal device that runs on merchant silicon.

  • whiteboard

    A whiteboard is a non-electronic variation of the traditional "rewriteable" schoolroom blackboard, but is white instead of black and of a material that can be written on with colored markers (known as dry erase markers).

  • whois

    whois is a program that will tell you the owner of any second-level domain name who has registered it with Verisign (or with Network Solutions, which was acquired by Verisign).

  • Wi-Fi Multimedia (WMM)

    Wi-Fi Multimedia (WMM), previously known as Wireless Multimedia Extensions (WME), is a subset of the 802.11e wireless LAN (WLAN) specification that enhances quality of service (QoS) on a network by prioritizing data packets according to four categories... (Continued)

  • Wide Area Application Services (WAAS)

    Wide Area Application Services (WAAS) is a Cisco Systems technology that improves the performance of applications on a wide area network (WAN). (Continued...)

  • Wide Area Ethernet (WAE)

    Wide Area Ethernet (WAE) or Ethernet WAN (also sometimes referred to as fiber or LAN extension service ) is a network carrier service that delivers high-speed wide area network (WAN) connectivity, utilizing Ethernet as the connection method. Positioned as an alternative to traditional wide area connections such as leased line, frame relay or T1 services, Wide Area Ethernet simplifies linking remote sites and enables bandwidth-heavy applications such as multicast video streaming.

  • wideband

    Wideband is a transmission medium or channel that has a wider bandwidth than one voice channel (with a carrier wave of a certain modulated frequency).

  • wideband audio (HD voice)

    Wideband audio, also known as HD voice, is a cellular technology that utilizes a wider frequency spectrum to achieve greater voice quality during phone calls.

  • wildcard mask

    A wildcard mask is a sequence of numbers that streamlines packet routing within the subnets of a proprietary network... (Continued)

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