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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  • N

    network performance monitoring (NPM)

    Network performance monitoring (NPM) is the process of measuring and monitoring the quality of service of a network.

  • network protocol

    A network protocol is a set of established rules that specify how to format, send and receive data so that computer network endpoints, including computers, servers, routers and virtual machines, can communicate despite differences in their underlying infrastructures, designs or standards.

  • network security

    Network security encompasses all the steps taken to protect the integrity of a computer network and the data within it.

  • network segmentation

    Network segmentation is a networking architectural design that divides a network into multiple segments (subnets) with each functioning as a smaller, individual network.

  • network service provider (NSP)

    A network service provider (NSP) is a company that owns, operates and sells access to internet backbone infrastructure and services.

  • network switch

    A network switch connects devices in a network to each other, enabling them to talk by exchanging data packets. Switches can be hardware devices that manage physical networks or software-based virtual devices.

  • Network Time Protocol (NTP)

    Network Time Protocol (NTP) is an internet protocol used to synchronize with computer clock time sources in a network.

  • network topology

    A network topology is the physical and logical arrangement of nodes and connections in a network.

  • network traffic

    Network traffic is the amount of data that moves across a network during any given time.

  • network visibility

    Network visibility is an awareness of the components and data within an enterprise computer network.

  • networking (computer)

    Networking, also known as computer networking, is the practice of transporting and exchanging data between nodes over a shared medium in an information system.

  • Next Hop Resolution Protocol (NHRP)

    Next Hop Resolution Protocol (NHRP) is an automated configuration technology that routes data on a distributed network by discovering the best routing path between endpoints.

  • NFV MANO (network functions virtualization management and orchestration)

    NFV MANO (network functions virtualization management and orchestration), also called MANO, is an architectural framework for managing and orchestrating virtualized network functions (VNFs) and other software components.

  • NFVi (network functions virtualization infrastructure)

    NFVi (network functions virtualization infrastructure) encompasses all of the networking hardware and software needed to support and connect virtual network functions in carrier networks.

  • NIS (Network Information System)

    NIS (Network Information System) is a network naming and administration system for smaller networks that was developed by Sun Microsystems.

  • nslookup

    Nslookup is the name of a program that lets users enter a host name and find out the corresponding IP address or domain name system (DNS) record.

  • NVGRE (Network Virtualization using Generic Routing Encapsulation)

    NVGRE (Network Virtualization using Generic Routing Encapsulation) is a network virtualization method that uses encapsulation to create large numbers of virtual LANs (VLANs) for subnets that can extend across dispersed data centers and Layers 2 and 3.

  • What is NetOps? Everything you need to know

    NetOps, also referred to as NetOps 2.0 and NetDevOps, is an approach to networking operations that uses DevOps tools and techniques to make network changes more efficiently and effectively than in the past.

  • What is network scanning? How to, types and best practices

    Network scanning is a procedure for identifying active devices on a network by employing a feature or features in the network protocol to signal to devices and await a response.

  • What is network virtualization? Everything you need to know

    Network virtualization is a method of combining the available resources in a network to consolidate multiple physical networks, divide a network into segments or create software networks between VMs.

  • O

    OFDMA (orthogonal frequency-division multiple access)

    Orthogonal frequency-division multiple access (OFDMA) is a technology of Wi-Fi 6 (802.11ax) that lets access points serve multiple clients at the same time.

  • ONOS (Open Network Operating System)

    Open Network Operating System (ONOS) is an OS designed to help network service providers build carrier-grade software-defined networks architected for high scalability, availability and performance.

  • open networking

    Open networking describes a network that uses open standards and commodity hardware.

  • Open Shortest Path First (OSPF)

    Open Shortest Path First, often shortened to OSPF, is an IP routing protocol used to find the best path to distribute packets as they pass through IP networks.

  • operational support system (OSS)

    An operational support system (OSS) is a set of programs that helps a communications service provider monitor, control, analyze and manage a telephone or computer network.

  • optoisolator (optical coupler or optocoupler)

    An optoisolator (also known as an optical coupler, photocoupler, optocoupler) is a semiconductor device that transfers an electrical signal between isolated circuits using light.

  • orthogonal frequency-division multiplexing (OFDM)

    Orthogonal frequency-division multiplexing (OFDM) is a method of data transmission where a single information stream is split among several closely spaced narrowband subchannel frequencies instead of a single wideband channel frequency.

  • OSGi (Open Service Gateway Initiative)

    The OSGi (Open Service Gateway Initiative) specification is a Java framework for developing and deploying modular software programs and libraries.

  • OSI model (Open Systems Interconnection)

    OSI (Open Systems Interconnection) is a reference model for how applications communicate over a network.

  • overlay network

    An overlay network is a virtual or logical network that is created on top of an existing physical network.

  • P

    packet filtering

    Packet filtering is the process of passing or blocking data packets at a network interface by a firewall based on source and destination addresses, ports or protocols.

  • packet loss

    Packet loss is when one or more transmitted data packets fail to arrive at their destination.

  • passive optical network (PON)

    A passive optical network (PON) is a system commonly used by telecommunications network providers that brings fiber optic cabling and signals all or most of the way to the end user.

  • patch panel

    A patch panel in a local area network (LAN) is a mounted hardware assembly that contains ports that are used to connect and manage incoming and outgoing LAN cables.

  • peer-to-peer (P2P)

    Peer-to-peer (P2P) is a decentralized communications model in which each party has the same capabilities and either party can initiate a communication session.

  • phase-locked loop (PLL)

    A phase-locked loop (PLL) is an electronic circuit with a voltage or voltage-driven oscillator that constantly adjusts to match the frequency of an input signal.

  • physical layer

    The physical layer is the first and lowest layer of the Open Systems Interconnection (OSI) communications model.

  • ping

    A ping (Packet Internet or Inter-Network Groper) is a basic internet program that enables a user to test and verify if a particular destination Internet Protocol (IP) address exists and can accept requests in computer network administration.

  • ping sweep (ICMP sweep)

    A ping sweep (also known as an ICMP sweep) is a basic network scanning technique used to determine which of a range of IP addresses map to live hosts (computers).

  • Plain Old Telephone Service (POTS)

    Plain Old Telephone Service (POTS) refers to the traditional, analog voice transmission phone system implemented over physical copper wires (twisted pair).

  • point-of-presence (POP)

    A point-of-presence (POP) is a point or physical location where two or more networks or communication devices build a connection from one place to the rest of the internet.

  • Point-to-Point Protocol (PPP)

    Point-to-Point Protocol (PPP) refers to a suite of computer communication protocols that provide a standard way to transport multiprotocol data over point-to-point links.

  • Point-to-Point Protocol over Ethernet (PPPoE)

    Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol that facilitates communication between network endpoints.

  • poison reverse

    In a computer network that uses the Routing Information Protocol (RIP) or other distance vector routing protocol, poison reverse is a loop avoidance process.

  • port

    A port in computing has three main uses, each as a type of receptacle in networking, computer hardware and software.

  • port address translation (PAT)

    Port address translation (PAT) is a type of network address translation (NAT) that maps a network's private internal IPv4 addresses to a single public IP address.

  • port number

    Port number is a way to identify a specific process to which an internet or other network message is to be forwarded when it arrives at a server.

  • Power over Ethernet (PoE)

    Power over Ethernet (PoE) is a technology for implementing wired Ethernet local area networks (LANs) that enables the electrical current necessary for operating each device to be carried by Ethernet data cables instead of standard electrical power cords and wiring.

  • preboot execution environment (PXE)

    Preboot execution environment (PXE), pronounced pixie, is a set of standards that enables a computer to load an operating system (OS) over a network connection.

  • presentation layer

    The presentation layer resides at Layer 6 of the Open Systems Interconnection (OSI) communications model and ensures that communications that pass through it are in the appropriate form for the recipient application.

  • private 5G

    Private 5G is a wireless network technology that delivers 5G cellular connectivity for private network use cases.

  • programmable network (network programmability)

    A programmable network is one in which the behavior of network devices and flow control is handled by software that operates independently of network hardware.

  • propagation delay

    Propagation delay is the amount of time required for a signal to be received after it has been sent; it is caused by the time it takes for the signal to travel through a medium.

  • What is a protocol data unit (PDU)?

    In networking, a protocol data unit is the basic unit of exchange between entities that communicate using a specified networking protocol.

  • What is PSTN (public switched telephone network)?

    The public switched telephone network, or PSTN, is the world's collection of interconnected voice-oriented public telephone networks.

  • Q

    QAM (quadrature amplitude modulation)

    QAM (quadrature amplitude modulation) is a method of combining two amplitude modulation (AM) signals into a single channel.

  • R

    radio frequency (RF, rf)

    Radio frequency (RF) is a measurement representing the oscillation rate of electromagnetic radiation spectrum, or electromagnetic radio waves, from frequencies ranging from 300 GHz to as low as 9 kHz.

  • Real-time Transport Protocol (RTP)

    Real-time Transport Protocol (RTP) is a network standard designed for transmitting audio or video data that is optimized for consistent delivery of live data.

  • remote infrastructure management

    Remote infrastructure management, or RIM, is a comprehensive approach to handling and overseeing an organization's IT infrastructure, systems and services from a remote location.

  • Reverse Address Resolution Protocol (RARP)

    Reverse Address Resolution Protocol (RARP) is a protocol a physical machine in a local area network (LAN) can use to request its IP address.

  • ROADM (reconfigurable optical add-drop multiplexer)

    An ROADM (reconfigurable optical add-drop multiplexer) is a device that can add, block, pass or redirect modulated infrared (IR) and visible light beams of various wavelengths in a fiber optic network. ... (Continued)

  • route summarization (route aggregation)

    Route summarization -- also known as route aggregation -- is a method to minimize the number of routing tables in an Internet Protocol (IP) network.

  • router

    A router is a physical or virtual appliance that passes information between two or more packet-switched computer networks.

  • Routing Information Protocol (RIP)

    Routing Information Protocol (RIP) is a distance vector protocol that uses hop count as its primary metric.

  • routing table

    A routing table is a set of rules, often viewed in table format, that's used to determine where data packets traveling over an Internet Protocol (IP) network will be directed.

  • RS-232C

    RS-232C is one of the earlier versions of the long-established standard RS-232, which defines a physical interface for relatively low-speed serial data communication between computers and related devices.

  • runbook

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

  • S

    SD-branch

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

  • SD-WAN security

    SD-WAN security refers to the practices, protocols and technologies protecting data and resources transmitted across software-defined wide area network infrastructure.

  • SDN controller (software-defined networking controller)

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

  • secure access service edge (SASE)

    Secure access service edge (SASE), pronounced sassy, is a cloud architecture model that bundles together network and cloud-native security technologies and delivers them as a single cloud service.

  • Seebeck effect

    The Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances.

  • 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

    The session layer is Layer 5 of the OSI communications model. It is the long-lived logical connection that persists between endpoints over time.

  • 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-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 for monitoring and managing network devices on a local area network (LAN) or wide area network (WAN).

  • single-user multiple input, multiple output (SU-MIMO)

    Single-user multiple input, multiple output (SU-MIMO) is a multitransmitter and receiver technology that lets a wireless access point send multiple, simultaneous data streams to one compatible endpoint at a time.

  • 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.

  • Snort

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

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • streaming network telemetry

    Streaming network telemetry is a real-time data collection service in which network devices, such as routers, switches and firewalls, continuously push data related to the network's health to a centralized location.

  • subcarrier

    A subcarrier is a secondary modulated signal frequency modulated into the main frequency (the carrier) to provide an additional channel of transmission.

  • subnet (subnetwork)

    A subnet, or subnetwork, is a segmented piece of a larger network. More specifically, subnets are a logical partition of an IP network broken into multiple, smaller network segments.

  • 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.