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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  • S

    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 North American standard for synchronous data transmission over 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.

  • What is SD-WAN (software-defined WAN)? Ultimate guide

    Software-defined WAN is a technology that uses software-defined networking concepts to distribute network traffic across a wide area network, or WAN.

  • T

    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 is a term that combines the words telecommunications and informatics to describe the use of communications and IT to transmit, store and receive information from devices to remote objects over a network.

  • Telnet

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

  • 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.

  • throughput

    Throughput is a measure of how many units of information a system can process in a given 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 is a data center architecture design in which computing equipment like servers, appliances and other switches located within the same or adjacent rack connect to an in-rack network switch.

  • 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 protocol on the internet that ensures the reliable transmission of data between devices on a network.

  • transport layer

    The transport layer is Layer 4 of the Open Systems Interconnection (OSI) communications model. It is responsible for ensuring that the data packets arrive accurately and reliably between sender and receiver.

  • 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 or port forwarding 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 public network's routing nodes are unaware that the transmission is part of a private network.

  • What is a 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.

  • What is 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.

  • U

    unshielded twisted pair (UTP)

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

  • User Datagram Protocol (UDP)

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

  • 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.

  • What is a URL (Uniform Resource Locator)?

    A URL (Uniform Resource Locator) is a unique identifier used to locate a resource on the internet.

  • What is the 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.

  • What is 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.

  • 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.

  • 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 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

    A virtual server, also known as a virtual machine (VM), is a partitioned space inside a real server and is transparent to users, replicating the functionality of a dedicated physical 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.

  • What is a VPN?

    A virtual private network (VPN) is a service that creates a safe, encrypted online connection.

  • W

    WAN (wide area network)

    A wide area network (WAN) is a geographically distributed private 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.

  • 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).

  • What is wavelength?

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

  • Wi-Fi 6E

    Wi-Fi 6E is one variant of the 802.11ax standard.

  • Wi-Fi 7

    Wi-Fi 7 is the pending 802.11be standard under development by IEEE.

  • 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.