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.

  • S

    single-user MIMO

    Single-user MIMO (SU-MIMO) is a multi-transmitter 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.

  • 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.

  • 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 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.

  • 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.

  • symmetric communications

    Compare asymmetric communications.

  • 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/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.

  • 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 stores 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.

  • Transmission Control Protocol (TCP)

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

  • 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.

  • 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

    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.

  • 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.

  • User Datagram Protocol (UDP)

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

  • 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)

    Variable Length Subnet Mask (VLSM) is a subnet -- a segmented piece of a larger network -- design strategy where all subnet masks can have varying sizes.

  • 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.

  • 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 software that operates like a physical network adapter within the host operating system (OS) or through an application installed on the endpoint or server.

  • 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 (VNFs)

    Virtual network functions (VNFs) are virtualized tasks formerly carried out by proprietary, dedicated hardware.

  • virtual networking

    Virtual networking is the abstraction of network resources from the underlying physical network infrastructure.

  • 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 virtual LAN (VLAN) is a logical overlay network that groups together a subset of devices that share a physical LAN, isolating the traffic for each group.

  • 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)

  • 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).

  • 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 optimization (WAN acceleration)

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

  • 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.

  • 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.

  • 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.

  • wireless mesh network (WMN)

    A wireless mesh network (WMN) is a mesh network created through the connection of wireless access point (WAP) nodes installed at each network user's locale.

  • wrap plug

    A wrap plug, also known as a loopback plug, is a special plug that can be inserted into a port on a communications device to perform a diagnostic test called a loopback test.

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