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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  • R

    RSVP (Resource Reservation Protocol)

    RSVP (Resource Reservation Protocol) is a set of communication rules that allows channels or paths on the Internet to be reserved for the multicast (one source to many receivers) transmission of video and other high-bandwidth messages.

  • runbook

    Runbooks are a set of standardized written procedures for completing repetitive IT processes within a company.

  • S

    satellite Internet connection

    A satellite Internet connection is an arrangement in which the upstream (outgoing) and the downstream (incoming) data are sent from, and arrive at, a computer through a satellite.

  • satellite news gathering (SNG)

    Satellite news gathering (SNG) is the use of mobile communications equipment for the purpose of worldwide newscasting.

  • SCART connector

    A SCART connector is a physical and electrical interconnection between two pieces of audio-visual equipment, such as a television set and a video cassette recorder (VCR).

  • SD-branch

    SD-branch is a single, automated, centrally managed software-centric platform that replaces or supplements an existing branch network architecture.

  • SD-WAN (software-defined WAN)

    Software-defined WAN (SD-WAN) is technology that uses software-defined networking (SDN) concepts to distribute network traffic across a wide area network (WAN).

  • SDN application (software-defined networking application)

    An SDN application is a software program designed to perform a task in a software-defined networking (SDN) environment. SDN applications can replace and expand upon functions that are implemented through firmware in hardware devices in a conventional networking environment.

  • SDN controller (software-defined networking controller)

    An SDN controller is an application in a software-defined networking (SDN) architecture that manages flow control for improved network management and application performance.

  • SDN overlay (software defined networking overlay)

    An SDN overlay is a deployment method for network virtualization and software-defined networking (SDN) that involves running a logically separate network or network component on top of existing infrastructure.

  • Secure Access Service Edge (SASE)

    Secure Access Service Edge, also known as SASE -- pronounced 'sassy' -- is a cloud architecture that bundles network and security solutions together and delivers them as a unified cloud service.

  • Seebeck effect

    The Seebeck effect describes the generation of electricity following the connection of two dissimilar electrical conductors or semiconductors that illustrates the thermoelectric effect. 

  • serial digital interface (SDI)

    Serial digital interface (SDI) is a standard for digital video and audio transmission over coaxial or fiber optic cabling.

  • Server Message Block protocol (SMB protocol)

    The Server Message Block protocol (SMB protocol) is a client-server communication protocol used for sharing access to files, printers, serial ports and other resources on a network.

  • Service Profile Identifier (SPID)

    In telecommunications, a Service Profile Identifier (SPID) is a number assigned by a phone company to a terminal on an Integrated Services Digital Network (ISDN) B-channel.

  • session border controller (SBC)

    A session border controller (SBC) is a dedicated hardware device or software application that governs the manner in which phone calls are initiated, conducted and terminated on a voice over Internet Protocol (VoIP) network.

  • Session layer

    In the Open Systems Interconnection (OSI) communications model, the session layer resides at Layer 5 and manages the setup and teardown of the association between two communicating endpoints.

  • session-based routing

    Session-based routing is a type of routing architecture that is application-centric and designed to route entire sessions instead of individual packets.

  • shielded twisted pair (STP)

    Shielded twisted pair (STP) is a special kind of copper telephone and local area network (LAN) wiring used in some business installations.

  • signal

    In electronics, a signal is an electric current or electromagnetic field used to convey data from one place to another.

  • signal-to-noise ratio (S/N or SNR)

    In analog and digital communications, a signal-to-noise ratio, often written S/N or SNR, is a measure of the strength of the desired signal relative to background noise (undesired signal).

  • Signaling System 7 (SS7)

    Signaling System 7 (SS7) is an international telecommunication protocol standard that defines how the network elements in a public switched telephone network (PSTN) exchange information and control signals.

  • Simple Network Management Protocol (SNMP)

    Simple Network Management Protocol (SNMP) is an application-layer protocol used to manage and monitor network devices and their functions.

  • Simputer (simple inexpensive mobile computer)

    The Simputer (short for simple inexpensive mobile computer) is an inexpensive, Web-enabled handheld computer designed for use by people in developing countries.

  • single-user MIMO

    Single-user MIMO (SU-MIMO) is a multi-transmitter and receiver technology for wireless communication that allocates the bandwidth of a wireless access point to a single device.

  • sliding window (windowing)

    The sliding window (windowing) technique is used by Transmission Control Protocol (TCP) to manage the flow of packets between two computers or network hosts.

  • small cell

    A small cell is an umbrella term used to describe a miniature radio access point or wireless network base station with a low radio frequency power output, footprint and range.

  • small form factor (SFF)

    Small form factor (SFF) refers to any of several physically compact connector designs that have been developed for use in fiber optic systems.

  • small form-factor pluggable (SFP)

    Small form-factor pluggable (SFP) is a specification for a new generation of optical modular transceivers.

  • Snort

    Snort is an open source network intrusion detection system (NIDS) created by Sourcefire founder and former CTO Martin Roesch.

  • softswitch

    Softswitch (software switch) is a generic term for any open application program interface (API) software used to bridge a public switched telephone network (PSTN) and Voice over Internet Protocol (VOiP) by separating the call control functions of a phone call from the media gateway (transport layer).

  • software-defined networking (SDN)

    Software-defined networking (SDN) is an architecture that abstracts different, distinguishable layers of a network to make networks agile and flexible.

  • software-defined networking monitoring application (SDN monitoring application)

    An SDN monitoring application is a software program that oversees the traffic in a software-defined network (SDN) as a component of network management.

  • Spanning Tree Protocol (STP)

    Spanning Tree Protocol (STP) is a Layer 2 network protocol used to prevent looping within a network topology.

  • spatial division multiple access (SDMA)

    Also see frequency division multiple access (FDMA) and time division multiple access (TDMA).

  • spectrum analyzer

    A spectrum analyzer is a device that measures and displays signal amplitude (strength) as it varies by frequency within its frequency range (spectrum).

  • split horizon

    Split horizon is a method used by distance vector protocols to prevent network routing loops.

  • splitter

    In telephony, a splitter, sometimes called a "plain old telephone service splitter," is a device that divides a telephone signal into two or more signals, each carrying a selected frequency range, and can also reassemble signals from multiple signal sources into a single signal.

  • spread spectrum

    Spread spectrum is a form of wireless communications in which the frequency of the transmitted signal is deliberately varied.

  • star network

    A star network is a local area network (LAN) topology in which all nodes -- personal computers (PCs), workstations or other devices -- are directly connected to a common central computer that is often referred to as a hub.

  • start of authority record

    A start of authority (SOA) record is information stored in a domain name system (DNS) zone about that zone and about other DNS records.

  • stateful inspection

    Stateful inspection, also known as dynamic packet filtering, is a firewall technology that monitors the state of active connections and uses this information to determine which network packets to allow through the firewall.

  • STDM (statistical time division multiplexing)

    STDM, or statistical time division multiplexing, is one method for transmitting several types of data simultaneously across a single transmission cable or line (such as a T1 or T3 line).

  • Stream Control Transmission Protocol (SCTP)

    Stream Control Transmission Protocol (SCTP) is a connection-oriented network protocol for transmitting multiple streams of data simultaneously between two endpoints that have established a connection in a network.

  • subcarrier

    A subcarrier is one telecommunication signal carrier that is carried on top of another carrier so that effectively two signals are carried at the same time.

  • subnet (subnetwork)

    A subnet, or subnetwork, is a segmented piece of a larger network.

  • subnetwork

    A subnetwork is a separately identifiable part of a larger network that typically represents a certain limited number of host computers, the hosts in a building or geographic area, or the hosts on an individual local area network.

  • Switched Multimegabit Data Service (SMDS)

    Switched Multimegabit Data Service (SMDS) is a public, packet-switched service aimed at enterprises that need to exchange large amounts of data with other enterprises over the wide area network on a nonconstant or bursty basis.

  • SYN scanning

    SYN scanning is a tactic that a malicious hacker can use to determine the state of a communications port without establishing a full connection.

  • Synchronous Data Link Control (SDLC)

    Synchronous Data Link Control (SDLC) is a transmission protocol used to synchronously transfer code-transparent, serial-by-bit data over a communications channel.

  • Synchronous Digital Hierarchy (SDH)

    Synchronous Digital Hierarchy (SDH) is a group of fiber optic transmission rates that transport digital signals with different capacities.

  • Synchronous Optical Network (SONET)

    Synchronous Optical Network (SONET) is a standard for synchronous data transmission on optical fibers.

  • system administrator (sysadmin)

    A system administrator (sysadmin) is an information technolog professional who supports a multiuser computing environment and ensures continuous, optimal performance of IT services and support systems.

  • T

    T-carrier system

    To see the relationship between T-carrier, E-carrier, and DS0 multiples, see digital signal X. The T-carrier system, introduced by the Bell System in the U.S. in the 1960s, was the first successful system that supported digitized voice transmission.

  • T1 (T-1)

    Also see the T-carrier system, of which the T1 is a part.

  • TCP (Transmission Control Protocol)

    TCP (Transmission Control Protocol) is a standard that defines how to establish and maintain a network conversation through which application programs can exchange data.

  • TCP/IP

    TCP/IP stands for Transmission Control Protocol/Internet Protocol and is a suite of communication protocols used to interconnect network devices on the internet.

  • telecommunications (telecom)

    Telecommunications, also known as telecom, is the exchange of information over significant distances by electronic means and refers to all types of voice, data and video transmission.

  • telematics

    Telematics uses GPS and mobile devices to send and receive information that helps control remote objects, primarily in the automotive industry.

  • telephone jacks

    In the U. S., telephone jacks are also known as registered jacks, sometimes described as RJ-XX, and are a series of telephone connection interfaces (receptacle and plug) that are registered with the U.S. Federal Communications Commission (FCC).

  • Telnet

    Telnet is a network protocol used to virtually access a computer and to provide a two-way, collaborative and text-based communication channel between two machines.

  • 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.

  • 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.

  • thin client (lean client)

    A thin client (or lean client) is a virtual desktop computing model that runs on the resources stored on a central server instead of a computer's resources.

  • 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.

  • 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 Division Multiple Access (TDMA)

    Time Division Multiple Access (TDMA) is a digital modulation technique used in digital cellular telephone and mobile radio communication.

  • time-to-live (TTL)

    Time-to-live (TTL) is a value for the period of time that a packet, or data, should exist on a computer or network before being discarded.

  • token ring

    A token ring is a data link for a local area network (LAN) in which all devices are connected in a ring or star topology and pass one or more tokens from host to host.

  • 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.

  • 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.

  • 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.

  • 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.

  • tree network

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

  • 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.

  • trunk (trunking)

    A network trunk is a communications line or link designed to carry multiple signals simultaneously to provide network access between two points.

  • tunneling or port forwarding

    Tunneling is the transmission of data intended for use only within a private, usually corporate network through a public network in such a way that the routing nodes in the public network are unaware that the transmission is part of a private network.

  • U

    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.

  • Universal Service Fund (USF)

    The Universal Service Fund (USF) is a United States government program that supports telecommunications access and affordability in rural and low-income communities.

  • 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.

  • 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

    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.

  • 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.

  • 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 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.

  • 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 routing and forwarding (VRF)

    Virtual routing and forwarding (VRF) is a technology included in Internet Protocol (IP) network routers that enables multiple instances of a routing table to exist in a virtual router and work simultaneously.

  • 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.

  • visitor-based networking (visitor-based network)

    Visitor-based networking (VBN) is a computer network with high-speed internet access provided by an organization for temporary use by visitors, guests or other users in a public area.

  • 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 a service that creates a safe, encrypted online connection.

  • VPN appliance

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

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