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• CSU/DSU (Channel Service Unit/Data Service Unit)

  A CSU/DSU (Channel Service Unit/Data Service Unit) is a hardware device about the size of an external modem that converts a digital data frame from the communications technology used on a local area network (LAN) into a frame appropriate to a ... Continue Reading

• CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance)

  CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is a protocol for carrier transmission in 802.11 networks. Continue Reading

• TCP/IP offload engine (TOE)

  The TCP/IP offload engine (TOE for short) is a technology that is gaining popularity in high-speed Ethernet systems for the purpose of optimizing throughput. Continue Reading

• traffic engineering

  Traffic engineering is a method of optimizing the performance of a telecommunications network by dynamically analyzing, predicting and regulating the behavior of data transmitted over that network... (Continued) Continue Reading

• Wi-Fi Multimedia (WMM)

  Wi-Fi Multimedia (WMM), previously known as Wireless Multimedia Extensions (WME), is a subset of the 802.11e wireless LAN (WLAN) specification that enhances quality of service (QoS) on a network by prioritizing data packets according to four ... Continue Reading

• Definitions to Get Started

  • TCP (Transmission Control Protocol)
  • wavelength
  • subnet (subnetwork)
  • UDP (User Datagram Protocol)

  • Telnet
  • VPN (virtual private network)
  • CIDR (Classless Inter-Domain Routing or supernetting)
  • Ethernet

  View All Definitions

• NBAR (Network Based Application Recognition)

  Network Based Application Recognition (NBAR) is a mechanism that classifies and regulates bandwidth for network applications to ensure that available resources are utilized as efficiently as possible. Cisco Systems developed NBAR as part of its ...Continue Reading

• 802.11 protocols

  Learn about the newest wireless protocol, 802.11n, as well as how to evaluate which protocol is best for your environment. You also get a run-down of the 802.11a, 802.11b and 802.11g specifications in this guide.Continue Reading

• Networking certification guide

  This networking certification guide covers the majority of networking-related certifications available to IT professionals. Only credentials likely to be recognized as having value within the networking industry have been selected, which led us to ...Continue Reading

• MOSPF (Multicast Open Shortest Path First)

  MOSPF (Multicast Open Shortest Path First) is an extension to the OSPF (Open Shortest Path First) protocol that facilitates interoperation between unicast and multicast routers... (Continued)Continue Reading

• 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.Continue Reading

• 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 ...Continue Reading

• Network management frameworks: FCAPS and ITIL

  Network management is a complex topic, especially as the network has to handle more instances of unified communications, video, and virtualization. Thus far, two frameworks exist that can be of some use for understanding and taming network ...Continue Reading

• Internet metering

  Internet metering is a service model in which an Internet service provider (ISP) tracks the customer's use of bandwidth and charges accordingly. Typically, the customer selects a service package with a flat rate up to a specified limit and pays,...Continue Reading

• tru2way

  Tru2way is the trade name for a technology that facilitates interactive TV and the convergence of digital television (DTV) with other communications devices... (Continued)Continue Reading

• OA&M (operations, administration, and management)

  OA&M (operations, administration, and management) is a general term used to describe the costs, tasks involved, or other aspects of operating, administering, and managing something such as a computer network.Continue Reading

• LAN server

  A local area network (LAN) server is a program (and by implication usually the computer it runs in) that "serves" the resources (files, storage, application programs, printers, and other devices) for a number of attached workstations.Continue Reading

• Learning Path: Network and Web Site Administration

  NETWORK AND WEB SITE ADMINISTRATION....network operations center (NOC) - internetworking - firewall - proxy server - DMZ - NAT - EGP - BGP - peering - colocation - IGP - DHCP - network operating system - Novell Directory Services (NDS) - nslookup - ...Continue Reading

• Learning Path: Telephony and Wide Area Networks

  TELEPHONY AND WIDE AREA NETWORKS...circuit - PSTN - Plain Old Telephone Service (POTS) - telephone jacks - dial-up - acoustic coupler - modem - 56flex - 56 Kbps (x2) - handshaking - V.xx standards - local loop - central office - LIDB - dedicated ...Continue Reading

• Ethernet Glossary

  After you've finished, you can test your knowledge with Quiz #28: Ethernet.Continue Reading

• IDSL

  IDSL is a system in which digital data is transmitted at 128 Kbps on a regular copper telephone line (twisted pair) from a user to a destination using digital (rather than analog or voice) transmission, bypassing the telephone company's central ...Continue Reading

• Learning Path: Network Infrastructure

  NETWORK INFRASTRUCTURE...infrastructure - backbone - network access point (NAP)- vBNS - Internet 2 - MAE - peering - router - switch - bridge - hub - stackable hub - repeater - brouter - aggregator - gateway - point-of-presence (POP) - colocation - ...Continue Reading

• NIS (Network Information System)

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

• IT Survival Kit: Networking refreshers

  Quick Network Security & Hardware Refreshers School is out for college students across the US, but the learning never stops for IT professionals.Continue Reading

• Optical Carrier levels (OCx)

  The Synchronous Optical Network (SONET) includes a set of signal rate multiples for transmitting digital signals on optical fiber.Continue Reading

• two-way server

  A two-way server is a server that incorporates a multi-core processor for increased performance... (Continued)Continue Reading

• flow routing

  Flow routing is a network routing technology that takes variations in the flow of data into account to increase routing efficiency... (Continued)Continue Reading

• 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)Continue Reading

• caller ID spoofing

  Caller ID spoofing is a service that allows a caller to masquerade as someone else by falsifying the number that appears on the recipient's caller ID display... (Continued)Continue Reading

• wavelength-division multiplexing (WDM)

  Wavelength-division multiplexing (WDM) is a method of combining multiple signals on laser beams at various infared (IR) wavelengths for transmission along fiber optic media. Each laser is modulated by an independent set of signals. ...Continue Reading

• Firewall implementation: Perimeter security placement and management

  For your enterprise firewall implementation, understand where your perimeter security goes, how many you need, what precautions to be aware of and know how to manage and maintain your firewall.Continue Reading

• How to choose the best firewall for your enterprise

  Learn how to choose the best firewall for your enterprise. This guide gives you purchasing advice, tells you which IT team is responsible for the perimeter security solution and offers a checklist of risks you must assess before making deciding ...Continue Reading

• ELF (extremely low frequency)

  ELF (extremely low frequency) refers to an electromagnetic field having a frequency much lower than the frequencies of signals typically used in communications.Continue Reading

• access point base station

  Access point base station is the original term for what is now known as a femtocell.Continue Reading

• bit stuffing

  Bit stuffing is the insertion of one or more bits into a transmission unit as a way to provide signaling information to a receiver... (Continued)Continue Reading

• Hayes command set

  Hayes command set is a specific programming language originally developed for the Hayes Smartmodem 300 baud modem during the late 1970s... (Continued)Continue Reading

• direct sequence spread spectrum (DSSS) or direct sequence code division multiple access (DS-CDMA)

  Direct sequence spread spectrum, also known as direct sequence code division multiple access (DS-CDMA), is one of two approaches to spread spectrum modulation for digital signal transmission over the airwaves.Continue Reading

• average revenue per user or average revenue per unit (ARPU)

  Average revenue per user or average revenue per unit (ARPU) is an expression of the income generated by a typical subscriber or device per unit time in a telecommunications network... (Continued)Continue Reading

• Wireless protocols learning guide

  Wireless protocols; technologies including 802.11, WLAN, WPA, WEP, Wi-Fi and wireless broadband; and deployment issues such as access points, security and troubleshooting are discussed in this guide designed to provide a basic introduction to ...Continue Reading

• Wireless network deployment and management

  Wireless network deployment and management are discussed in this guide.Continue Reading

• Wireless troubleshooting

  Wireless network troubleshooting basics are discussed in this guide.Continue Reading

• Wireless access points

  The basics of wireless access point (AP) as well as configuration and placement are covered in this guide.Continue Reading

• Developing good troubleshooting technique -- from 'Network troubleshooting and diagnostics'

  The most important part of troubleshooting is developing a good technique. This excerpt from "Network troubleshooting and diagnostics" lays the foundation for developing a good technique by examining approaches such as using the OSI model as a ...Continue Reading

• Network engineering applications -- from 'Network troubleshooting and diagnostics'

  Learn about network engineering and analysis applications that can be used when a high-level approach is needed to understand how the network system as a whole operates, both within each individual device and between the internal network and any ...Continue Reading

• IP address management -- from 'Network troubleshooting and diagnostics'

  Learn how IP address management and maintenance tools can help manage the scope of IP addresses on your network. With typical Class C subnets consuming upwards of 254 addresses per subnet and most companies needing multiple subnets, the sheer ...Continue Reading

• Tool suites for identifying the problem -- from 'Network troubleshooting and diagnostics'

  A baker can't bake a cake without a good cake pan, and a mechanic won't get very far in fixing your car without a solid wrench set. Though the tools for network administrators are different and more difficult to wrap your hands around than these ...Continue Reading

• Network troubleshooting and diagnostics: Introduction

  Network troubleshooting and diagnostics begins with realizing that there is a problem and then finding out what that problem really is. Once you know the root cause of the problem, the resolution is usually a Google search away. But finding that ...Continue Reading

• comfort noise generator (CNG)

  A comfort noise generator (CNG) is a program used to generate background noise artificially for voice communications during periods of silence that occur during the course of conversation... (Continued)Continue Reading

• netstat

  Netstat is a common command line TCP/IP networking utility available in most versions of Windows, Linux, UNIX and other operating systems... (Continued)Continue Reading

• Ethernet as a service (EaaS)

  Ethernet as a service (EaaS) is the use of high-bandwidth, fiber optic media such as Packet over SONET (PoS) to deliver 10 Mbps, 100 Mbps or even 1000 Mbps Ethernet service to one or more customers across a common bidirectional broadband ...Continue Reading

• Cisco Information Security Specialist (CISS)

  Cisco Information Security Specialist (CISS) is an entry-level certification attesting that the holder has demonstrated the foundational knowledge and skills required to install and support a Cisco Self-Defending Network... (Continued)Continue Reading

• network coding

  Network coding is a method of optimizing the flow of digital data in a network by transmitting digital evidence about messages... (Continued)Continue Reading

• 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.Continue Reading

• Carrier Ethernet

  Carrier Ethernet is the use of high-bandwidth Ethernet technology for Internet access and for communication among business, academic and government local area networks (LANs)... (Continued)Continue Reading

• video on demand (VoD)

  Video on demand (VoD) is an interactive TV technology that allows subscribers to view programming in real time or download programs and view them later... (Continued)Continue Reading

• multichassis multilink PPP (MMP)

  Multichassis multilink PPP (MMP) is an extension of multilink PPP (MP) in which the subscriber can consist of more than one computer... (Continued)Continue Reading

• triple-play network

  A triple-play network is one in which voice, video and data are all provided in a single access subscription... (Continued)Continue Reading

• multilink PPP

  Multilink PPP is a communications protocol that enables a personal computer (PC) to use two PPP (Point-to-Point Protocol) communications ports as if they were a single port of greater bandwidth... (Continued)Continue Reading

• operational support system (OSS)

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

• DSLAM (Digital Subscriber Line Access Multiplexer)

  A DSLAM (Digital Subscriber Line Access Multiplexer) is a network device, usually at a telephone company central office, that receives signals from multiple customer Digital Subscriber Line (DSL) connections and puts the signals on a high-speed ...Continue Reading

• 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.Continue Reading

• backbone

  A backbone is a larger transmission line that carries data gathered from smaller lines that interconnect with it.Continue Reading

• cable TV or CATV (community antenna television)

  Cable TV is also known as "CATV" (community antenna television).Continue Reading

• 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.Continue Reading

• peering

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

• 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)Continue Reading

• IP Multimedia Subsystem (IMS)

  The IP Multimedia Subsystem (IMS) is a concept for an integrated network of telecommunications carriers that would facilitate the use of IP (Internet Protocol) for packet communications in all known forms over wireless or landline... (Continued)Continue Reading

• carrier signal

  A carrier signal is a transmitted electromagnetic pulse or wave at a steady base frequency of alternation on which information can be imposed by increasing signal strength, varying the base frequency, varying the wave phase, or other means... (...Continue Reading

• broadband

  In general, broadband refers to telecommunication in which a wide band of frequencies is available to transmit information.Continue Reading

• inverse multiplexing over ATM (IMA)

  Inverse multiplexing over ATM (IMA) is a method of optimizing the data transfer rate for individual subscribers in networks that use asynchronous transfer mode (ATM) by dividing the data into multiple concurrent streams that are sent across separate...Continue Reading

• telecom carrier

  A telecom carrier is a company that is authorized by regulatory agencies to operate a telecommunications system.Continue Reading

• carrier detect

  Carrier detect (see modem lights) is a control signal between a modem and a computer that indicates that the modem detects a "live" carrier that can be used for sending and receiving information.Continue Reading

• Cisco CCIP MPLS certification: Introduction

  Learn skills required for the MPLS portion of the Cisco CCIP certification. These skills are tested in the CCIP 642-611 -- Implementing Cisco MPLS Exam.Continue Reading

• erlang

  The Erlang programming language is not the same thing as the erlang, a unit of traffic density.Continue Reading

• Cisco certification

  This Cisco certifications guide covers CCNA, CCNP, CCIE and more. Decide whether getting a Cisco certification is necessary for your career, which one you should get and how to study and pass your exam.Continue Reading

• fiber jumper

  A fiber jumper, sometimes called a fiber patch cord is a length of fiber cabling fitted with LC, SC, MTRJ or ST connectors at each end... (Continued)Continue Reading

• 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.Continue Reading

• staggered quadrature phase-shift keying

  Staggered quadrature phase-shift keying (SQPSK), also known as offset quadrature phase-shift keying (OQPSK), is a method of phase-shift keying (PSK) in which the signal carrier-wave phase transition is always 90 degrees or 1/4 cycle at a time... (...Continue Reading

• KVM switch (keyboard, video, mouse switch)

  A KVM (keyboard, video, mouse) switch is a hardware device that allows a user to control multiple computers from a single keyboard, video display monitor and mouse.Continue Reading

• concentrator

  As generally used, a concentrator is a device that acts as an efficient forwarder of data transmission signals.Continue Reading

• flooding

  In a network, flooding is the forwarding by a router of a packet from any node to every other node attached to the router except the node from which the packet arrived.Continue Reading

• Audiobook: Intrusion Prevention Fundamentals

  Intrusion Prevention Fundamentals: An introduction to network attack mitigation with IPSContinue Reading

• AppleTalk

  AppleTalk is a set of local area network communication protocols originally created for Apple computers.Continue Reading

• AMTOR (amateur teleprinting over radio)

  AMTOR (amateur teleprinting over radio) is a digital communications method used by radio amateurs, in which the frequency of errors is reduced by handshaking or character repetition.Continue Reading

• automatic repeat request (ARQ)

  Automatic repeat request (ARQ) is a protocol for error control in data transmission.Continue Reading

• IS-IS (Intermediate System-to-Intermediate System protocol)

  One of the most commonly used routing protocols, the Intermediate System-to-Intermediate System protocol (IS-IS) is based on a routing method known as DECnet Phase V routing, in which routers known as intermediate systems exchange data about routing...Continue Reading

• autotrunking

  Autotrunking is a function that can be activated for one or more switch ports in a Cisco system of virtual local area networks (VLANs), making those ports capable of carrying traffic for any or all of the VLANs accessible by a particular switch....Continue Reading

• virtual systems management (VSM)

  Virtual systems management (VSM), also known as virtual system management, is the process of remotely managing the allocation and use of resources in conventional networks as well as in virtual area networks (VANs), virtual private networks (VPNs), ...Continue Reading

• GVRP (GARP VLAN Registration Protocol or Generic VLAN Registration Protocol)

  GVRP (GARP VLAN Registration Protocol or Generic VLAN Registration Protocol) is a protocol that facilitates control of virtual local area networks (VLANs) within a larger network . GVRP conforms to the IEEE 802.1Q specification, which defines a ...Continue Reading

• VxWorks

  VxWorks is a real-time operating system (RTOS) that can be used in embedded systems... (Continued)Continue Reading

• Network administration guide

  Good network administration is the backbone of today's technology-dependent enterprises. Network administrators are charged with keeping expansive networks and numerous applications running smoothly, and the job can seem overwhelming at times. We're...Continue Reading

• BGAN (Broadband Global Area Network)

  BGAN (Broadband Global Area Network) is a mobile communications system created to transmit broadband wireless voice and data communications almost anywhere on the earth's surface.Continue Reading

• Metcalfe's Law

  Metcalfe's Law is expressed in two general ways: The number of possible cross-connections in a network grow as the square of the number of computers in the network increases.Continue Reading

• wildcard mask

  A wildcard mask is a sequence of numbers that streamlines packet routing within the subnets of a proprietary network... (Continued)Continue Reading

• fixed-length subnet mask (FLSM)

  A fixed-length subnet mask (FLSM) is a sequence of numbers of unchanging length that streamlines packet routing within the subnets of a proprietary network... (Continued)Continue Reading

• Managing Windows networks using scripts -- The basics

  Learning to use scripts can make the life of a network administrator a lot easier by allowing you to automate daily administration tasks. This tip begins a series on using scripts to manage Windows networks.Continue Reading

• Next Steps in Signaling (NSIS)

  NSIS (Next Steps in Signaling) is an evolving communication protocol intended to facilitate signaling at the Transport layer, using a two-level model to support diverse services and resources... (Continued)Continue Reading

• baseboard management controller (BMC)

  A baseboard management controller (BMC) is a specialized service processor that monitors the physical state of a computer, network server or other hardware device using sensors and communicating with the system administrator through an independent ...Continue Reading

• packet loss

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

• Traversal Using Relay NAT (TURN)

  Traversal Using Relay NAT (TURN) is a protocol, currently at the working draft stage, that is intended to govern the reception of data over a Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) connection by a single communications ...Continue Reading

• delay-tolerant network

  A delay-tolerant network is a network designed to operate effectively over extreme distances such as those encountered in space communications or on an interplanetary scale... (Continued)Continue Reading