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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  • O

    out-of-band signaling

    Out-of-band signaling is telecommunication signaling (exchange of information in order to control a telephone call) that is done on a channel that is dedicated for the purpose and separate from the channels used for the telephone call.

  • over-the-top (OTT)

    Over-the-top (OTT) is networking lingo that describes the delivery of content, services or applications over the internet.

  • overlay network

    An overlay network is a telecommunications network that is built on top of another network and is supported by its infrastructure.

  • OVSDB (Open vSwitch Database Management Protocol)

    The Open vSwitch Database Management Protocol (OVSDB) is an OpenFlow configuration protocol that is designed to manage Open vSwitch implementations.

  • P

    packet filtering

    On the Internet, packet filtering is the process of passing or blocking packets at a network interface based on source and destination addresses, ports, or protocols.

  • packet loss

    Packet loss is the failure of one or more transmitted packets to arrive at their destination... (Continued)

  • packet mangling

    Packet mangling is the modification of packets at a packet-based network interface before and/or after routing.

  • Packet Order Correction (POC)

    Packet Order Correction (POC) is a technique for dealing with out-of-order packet delivery.

  • Packet-Level Procedure (PAP)

    PAP (Packet-Level Procedure) is a full-duplex protocol for transferring packets between parties in an X.25 network.

  • packet-switched

    Packet-switched describes the type of network in which relatively small units of data called packets are routed through a network based on the destination address contained within each packet.

  • PacketHound

    PacketHound is a product that aims to help an enterprise regulate traffic that might otherwise slow services down for all users of a local area network.

  • PAIR (Policy Analysis of Internet Routing)

    The Policy Analysis of Internet Routing (PAIR) project is a Merit Network initiative dedicated to developing tools that Internet service providers (ISPs), network operators, and end users can use to troubleshoot Internet routing and policy problems.

  • Parlay

    Parlay (pronounced PAHR-LAY as in the French verb "parler" - to speak) is an evolving set of specifications for industry-standard application programming interfaces (APIs) for managing network "edge" services such as call control, messaging, and content-based charging.

  • passive FTP

    Passive FTP (sometimes referred to as PASV FTP because it involves the FTP PASV command) is a more secure form of data transfer in which the flow of data is set up and initiated by the File Transfer Program (FTP) client rather than by the FTP server program.

  • passive optical network (PON)

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

  • patch antenna

    A patch antenna is a wafer-like directional antenna suitable for covering single-floor small offices, small stores and other indoor locations where access points cannot be placed centrally.

  • patch cord

    A patch cord is a length of cable, with connectors on the ends, that is used to connect an end device to something else, such as a power source.

  • patch panel

    A network patch panel is a mounted hardware unit containing ports used to interconnect and manage LAN cables as well as connect them to the internet and wide area networks.

  • path

    In a computer operating system, a path is the route through a file system to a particular file.

  • Path Computation Element (PCE)

    Path Computation Element (PCE) is a network component, application or node that can apply computational constraints and compute a network path or route based on a network graph. The PCE has access to topology information for the entire network and uses this in path computations.

  • PCS (personal communications service)

    PCS (personal communications service) is a wireless phone service similar to cellular telephone service but emphasizing personal service and extended mobility. (Continued...)

  • 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.

  • peering

    Peering is the arrangement of traffic exchange between Internet service providers (ISPs).

  • Peltier effect

    The Peltier effect is a temperature difference created by applying a voltage between two electrodes connected to a sample of semiconductor material. This phenomenon can be useful when it is necessary to transfer heat from one medium to another on a small scale... (Continued)

  • permanent virtual circuit (PVC)

    A permanent virtual circuit (PVC) is a software-defined logical connection in a network such as a frame relay network.

  • Personal Access Communications System (PACS)

    Personal Access Communications System (PACS) is a type of wireless telephone network compatible with telephone sets, answering machines, fax machines, and computers.

  • petabit

    A petabit is one quadrillion (1015) binary digits and is used in discussing possible volumes of data traffic per second in a large telecommunications network.

  • phantom dialing

    In mobile wireless communication, phantom dialing is a term used to describe what occurs when a user unintentionally presses a pre-programmed auto-dial number on their cellular telephone keypad and unintentionally initiates a phone call.

  • phase-change cooling (vapor cooling)

    Phase-change cooling, also called vapor cooling, is a microprocessor-cooling technology that works according to the same principles as a conventional refrigerator, freezer or air conditioner. The principal components of a phase-change cooling system are the compressor (or condenser), the vaporizer, the radiating element and the pump... (Continued)

  • phase-locked loop

    A phase-locked loop (PLL) is an electronic circuit with a current-driven oscillator that constantly adjusts to match the frequency of an input signal, often used in wireless systems.

  • phase-shift keying (PSK)

    Phase-shift keying (PSK) is a method of digital communication in which the phase of a transmitted signal is varied to convey information.

  • Phone numbers

    Resources for looking up phone numbers.

  • physical layer

    Located at the lowest layer of the Open Systems Interconnection (OSI) communications model, the physical layer's function is to transport data using electrical, mechanical or procedural interfaces.

  • ping

    Ping is a basic Internet program that allows a user to verify that a particular IP address exists and can accept requests. The verb "ping" means the act of using the ping utility or command.

  • 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)

    POTS is a term sometimes used in discussion of new telephone technologies in which the question of whether and how existing voice transmission for ordinary phone communication can be accommodated.

  • plesiochronous

    Plesiochronous (pronounced plee-see-AH-krun-us, from Greek plesos, meaning close, and chronos, meaning time) is an adjective that describes operations that are almost, but not quite, in synchronization - in other words, almost synchronous.

  • Plexxi

    Plexxi is a Cambridge Massachusetts company that makes software-defined networking (SDN) software. The company was founded with venture-based funding in 2011. Plexxi's management team is composed of networking professionals.

  • point-of-presence (POP)

    On the Internet, a point-of-presence (POP) is an access point from one place to the rest of the Internet.

  • Point-to-Point Tunneling Protocol (PPTP)

    Point-to-Point Tunneling Protocol (PPTP) is a protocol (set of communication rules) that allows corporations to extend their own corporate network through private "tunnels" over the public Internet.

  • poison reverse

    In a computer network that uses the Routing Information Protocol (RIP) or other distance vector routing protocols, a poison reverse is a way in which a gateway node tells its neighbor gateways that one of the gateways is no longer connected.

  • Policy and Charging Rules Function (PCRF)

    Policy and Charging Rules Function (PCRF) is the part of the Evolved Packet Core (EPC) that supports service data flow detection, policy enforcement and flow-based charging.

  • policy-based networking

    Policy-based networking is the management of a network so that various kinds of traffic - data, voice, and video - get the priority of availability and bandwidth needed to serve the network's users effectively.

  • port

    On computer and telecommunication devices, a port (noun) is generally a specific place for being physically connected to some other device, usually with a socket and plug of some kind.

  • port 80

    On a Web server or Hypertext Transfer Protocol daemon, port 80 is the port that the server "listens to" or expects to receive from a Web client, assuming that the default was taken when the server was configured or set up.

  • Port Address Translation (PAT)

    Port Address Translation (PAT), is an extension to network address translation (NAT) that permits multiple devices on a local area network (LAN) to be mapped to a single public IP address. The goal of PAT is to conserve IP addresses.

  • port interface card (PIC)

    A port interface card (PIC) is a computer circuit board that provides multiple, diverse interfaces for connections to external networks. In effect, a PIC is an enhanced network interface card (NIC)... (Continued)

  • port mirroring (roving analysis port)

    Port mirroring is an approach to monitoring network traffic that involves forwarding a copy of each packet from one network switch port to another.

  • port number

    A 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 wired Ethernet local area networks (LANs) that allows the electrical current necessary for the operation of each device to be carried by the data cables rather than by power cords.

  • POX

    POX is an open source development platform for Python-based software-defined networking (SDN) control applications, such as OpenFlow SDN controllers.

  • PPP (Point-to-Point Protocol)

    PPP (Point-to-Point Protocol) is a standard used to establish a direct connection between two network nodes that enables the transport of multiprotocol data.

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

    PPPoE (Point-to-Point Protocol over Ethernet) is a specification for connecting multiple computer users on an Ethernet local area network to a remote site through common customer premises equipment, which is the telephone company's term for a modem and similar devices.

  • Preboot Execution Environment (PXE)

    The Preboot Execution Environment (PXE) is an industry standard client/server interface that allows networked computers that are not yet loaded with an operating system to be configured and booted remotely by an administrator.

  • predictive dialer

    A predictive dialer is a telephone control system that automatically calls a list of telephone numbers in sequence, screening out no-answers, busy signals, answering machines and disconnected numbers while predicting at what point a human caller will be able to handle the next call.

  • presentation layer

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

  • Primary Rate Interface (PRI)

    In the Integrated Services Digital Network (ISDN), there are two levels of service: the Basic Rate Interface (BRI), intended for the home and small enterprise, and the Primary Rate Interface (PRI), for larger users.

  • private automatic branch exchange (PABX)

    A private automatic branch exchange (PABX) is an automatic telephone switching system within a private enterprise.

  • programmable network (PN)

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

  • propagation delay

    Propagation delay, symbolized tpd, is the time required for a digital signal to travel from the input(s) of a logic gate to the output.

  • protocol-independent multicast (PIM)

    Protocol-independent multicast (PIM) is a set of four specifications that define modes of Internet multicasting to allow one-to-many and many-to-many transmission of information... (Continued)

  • pseudowire

    Pseudowire ( sometimes spelled as pseudo wire or abbreviated as PW) is a mechanism for emulating various networking or telecommunications services across packet-switched networks using Ethernet, IP, or MPLS... (Continued)

  • PSTN (public switched telephone network)

    PSTN (public switched telephone network) is the world’s collection of interconnected voice-oriented public telephone networks.

  • pulse code modulation (PCM)

    Pulse code modulation (PCM) is a digitalscheme for transmitting analogdata.

  • Q

    QAM (quadrature amplitude modulation)

    QAM (quadrature amplitude modulation) is a method of combining two amplitude-modulated (AM) signals into a single channel, thereby doubling the effective bandwidth.

  • Quad FastEthernet (QFE)

    Quad FastEthernet (QFE) is a network interface card (NIC) manufactured by Sun Microsystems that is designed to enhance the bandwidth of a Peripheral Component Interconnect (PCI)-based server using Sun Microsystem's Solaris 8 or later operating environment.

  • quadruple-play network

    A quadruple-play network is one that offers mobility in addition to the voice, data and video provided by a triple play network.

  • queries-per-second (QPS)

    Queries-per-second (QPS) (or the query-per-second rate) is a measure of how much traffic a particular query server is handling at a given time.

  • R

    radio access network (RAN)

    A radio access network (RAN) is the part of a telecommunications system that connects individual devices to other parts of a network through radio connections.

  • radio frequency (RF, rf)

    Radio frequency 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.

  • RCA connector

    An RCA connector is a plug and a jack designed for use with coaxial cable for frequencies ranging from the very lowest up to several megahertz.

  • Real-Time Transport Protocol (RTP)

    The Real-Time Transport Protocol (RTP) is an Internet protocol standard that specifies a way for programs to manage the real-time transmission of multimedia data over either unicast or multicast network services.

  • red route

    A red route is one of three categories of Internet route states defined by the Policy Analysis of Internet Routing (PAIR) project, an initiative dedicated to the development of tools that ISPs (Internet service providers), network operators, and end users can use to troubleshoot Internet routing and policy problems.

  • Regional Internet Registry (RIR)

    A Regional Internet Registry (RIR) is a not-for-profit organization that oversees Internet Protocol (IP) address space and the Autonomous System (AS) numbers within a specific geographical region. Each RIR is tasked with creating local policy for managing the finite number of identity elements (unique addresses and numbers) that routers, switches and computers use on the Internet.

  • registered port numbers

    The registered port numbers are the port numbers that companies and other users register with the Internet Corporation for Assigned Names and Numbers (ICANN) for use by the applications that communicate using the Internet's Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP).

  • repeater

    In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium.

  • Resilient Packet Ring (RPR)

    Resilient Packet Ring (RPR) is a network topology being developed as a new standard for fiber optic rings.

  • response time

    According to the IBM Dictionary of Computing (which cites International Organization for Standardization Information Technology Vocabulary as the source), response time is: The elapsed time between the end of an inquiry or demand on a computer system and the beginning of a response; for example, the length of the time between an indication of the end of an inquiry and the display of the first character of the response at a user terminal.

  • Reverse Address Resolution Protocol (RARP)

    RARP (Reverse Address Resolution Protocol) is a protocol by which a physical machine in a local area network can request to learn its IP address from a gateway server's Address Resolution Protocol (ARP) table or cache.

  • reverse DNS (rDNS)

    Reverse DNS (rDNS) is a method of resolving an IP address into a domain name, just as the domain name system (DNS) resolves domain names into associated IP addresses.

  • reverse Telnet (direct Telnet)

    Reverse Telnet (sometimes called direct Telnet) is the initiation of a Telnet session from a computer system to one of its remote users.

  • ring

    A ring is a network topology or circuit arrangement in which each device is attached along the same signal path to two other devices, forming a path in the shape of a ring.

  • rlogin (remote login)

    Rlogin (remote login) is a UNIX command that allows an authorized user to login to other UNIX machines (hosts) on a network and to interact as if the user were physically at the host computer.

  • RNIS (Reseau Numerique a Integration de Services)

    RNIS (Reseau Numerique a Integration de Services) is the European name for Integrated Services Digital Network (ISDN).

  • 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)

  • root directory

    In a computer file system that is organized as a hierarchy or tree, the root directory is the directory that includes all other directories.

  • root server system

    On the Internet, the root server system is the way that an authoritative master list of all top-level domain names (such as com, net, org,and individual country codes) is maintained and made available to all routers.

  • round-trip time (RTT)

    Round-trip time (RTT), also called round-trip delay, is the time required for a signal pulse or packet to travel from a specific source to a specific destination and back again...(Continued)

  • route aggregation

    Route aggregation is an alternate term for route summarization, which is a method used to minimize the number of routing tables required in an IP network.

  • route poisoning

    Route poisoning is a method of preventing a network from sending packets through a route that has become invalid.

  • route summarization (route aggregation)

    Route summarization, also called route aggregation, is a method of minimizing the number of routing tables in an IP (Internet Protocol) network. It works by consolidating selected multiple routes into a single route advertisement, in contrast to flat routing in which every routing table contains a unique entry for each route... (Continued)

  • router

    A router is a physical or virtual appliance that passes information between two or more packet-switched computer networks. A router inspects a given data packet's destination IP address, calculates the best way for it to reach its destination and then forwards it accordingly.

  • Routing Information Protocol (RIP)

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

  • routing switch

    In a network, a 'routing switch' is a device that combines the functions of a switch, which forwards data by looking at a physical device address, and a router, which forwards packets by locating a next hop address.

  • routing table

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

  • RS-232C

    RS-232C is a long-established standard ("C" is the current version) that describes the physical interface and protocol for relatively low-speed serial data communication between computers and related devices.

  • 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.

  • rule base

    In the context of a computer server acting as a firewall, a rule base is a set of rules that govern what is and what is not allowed through the firewall.

  • run book

    In a computer system or network, a run book is a written set of procedures for the routine and exceptional operation of the system or network by an administrator or operator.

  • running disparity (RD)

    Running disparity (RD or rd) is the difference between the number of logic 1 bits and logic 0 bits between the start of a data sequence and a particular instant in time during its transmission.

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