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• cyclic redundancy checking

  Cyclic redundancy checking is a method of checking for errors in data that has been transmitted on a communications link. Continue Reading

• customer premises equipment (CPE)

  Customer premises equipment (CPE) is telephone or other service provider equipment that is located on the customer's premises (physical location) rather than on the provider's premises or in between. Continue Reading

• Broadband over Power Line (BPL)

  Broadband over Power Line (BPL) is a technology that allows Internet data to be transmitted over utility power lines. Continue Reading

• baud

  Baud was the prevalent measure for data transmission speed until replaced by a more accurate term, bps (bits per second). Continue Reading

• bits per second (bps or bit/sec)

  In data communications, bits per second (abbreviated bps or bit/sec) is a common measure of data speed for computer modems and transmission carriers. Continue Reading

• Definitions to Get Started

  • Network layer
  • SD-WAN (software-defined WAN)
  • wireless mesh network (WMN)
  • 3G (third generation of mobile telephony)

  • WAN (wide area network)
  • firewall as a service (FWaaS)
  • CDMA (Code-Division Multiple Access)
  • ICMP (Internet Control Message Protocol)

  View All Definitions

• Cloud computing network primer

  Cloud computing network architecture is moving toward a flat, leaf-spine topology, enabling reduced latency and balancing bandwidth, providing any-to-any connectivity within and between servers. Learn more in this primer.Continue Reading

• VLAN guide for networking professionals

  Virtual LANs (VLANs) are LANs with definitions that map workstations based on anything except for geographic location. In this VLAN guide, you will learn about VLANs as they relate to server virtualization and WLANs and find VLAN configuration tips ...Continue Reading

• Evaluating Citrix Branch Repeater for WAN optimization

  Citrix's product for WAN optimization is the Citrix Branch Repeater. This family of products integrates network optimization with application, desktop and server virtualization.Continue Reading

• Evaluating Blue Coat Systems' WAN optimization

  Blue Coat Systems distinguishes itself as a WAN optimization vendor with strengths in security and application visibility. Learn important facts about Blue Coat's ProxySG and PacketShaper products.Continue Reading

• Evaluating Silver Peak Systems for WAN optimization

  Silver Peak Systems' WAN optimization product line addresses problems typically seen in the data center, including accelerating data backup, server and storage centralization, and real-time collaboration and virtual desktop infrastructure (VDI).Continue Reading

• Evaluating Ipanema Technologies' WAN optimization

  Ipanema Technologies provides WAN optimization to system integrators, VARs, and service providers. It offers extensive performance management in addition to acceleration and optimization technology.Continue Reading

• WAN optimization vendors: Comparison methodology and snapshot

  We polled the major WAN optimization vendors for product information and compiled it to help you make a vendor comparison. Here we list the main differences between WOC providers, in brief.Continue Reading

• Evaluating Riverbed Steelhead WAN optimization

  Riverbed Steelhead appliances for WAN optimization are focused on specific enterprise applications -- such as rich media, thin clients, Web apps and disaster recovery -- scalability and ease of installation.Continue Reading

• Evaluating Cisco WAAS WAN optimization

  Cisco WAAS is a family of WAN optimization products that integrate well into the network environment and offers broad application support through Cisco's partnerships.Continue Reading

• 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 ...Continue Reading

• Bandwidth measurement and management guide

  Today's enterprise applications are demanding more and more network bandwidth. How do you ensure you have enough bandwidth and manage it well? Find out with the resources in our bandwidth measurement and management guide.Continue Reading

• IP network design guide: Managing an IP-based network

  Network design underlies the performance of your enterprise IP network. This four part guide by Cormac Long offers you a comprehensive roadmap to designing IP-based networks, from the basic principles involved to the more complex finishing touches.Continue Reading

• logical network

  A logical network is one that appears to the user as a single, separate entity although it might in fact be either just a part of a larger network or an entity connecting multiple networks. A logical network is defined by its IP addressing scheme.Continue Reading

• WAN accelerator

  A WAN accelerator is an appliance that improves the end user's experience on a wide area network (WAN).Continue Reading

• chatty protocol

  A chatty protocol is an application or routing protocol that requires a client or server to wait for an acknowledgement before it can transmit again.Continue Reading

• Packet Order Correction (POC)

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

• transparent addressing

  On a wide area network (WAN), transparent addressing is a method of network addressing in which all intermediate node addresses are spoofed, so the client and server see each other's addresses and port configurations as if there were no intermediate...Continue Reading

• 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.Continue Reading

• WAN clustering (geoclustering, high-availability clustering or remote clustering)

  WAN clustering, also called geoclustering, high-availability clustering or remote clustering, is the use of multiple redundant computing resources located in different geographical locations to form what appears to be a single highly-available ...Continue Reading

• stateful inspection

  Stateful inspection 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. Stateful inspection is also known as dynamic packet filtering.Continue Reading

• green networking

  Green networking is the practice of selecting energy-efficient networking technologies and products, and minimizing resource use whenever possible.Continue Reading

• beamforming

  Beamforming is a type of RF (radio frequency) management in which an access point uses multiple antennas to send out the same signal.Continue Reading

• Network change and configuration management primer

  With network change and configuration management (NCCM), enterprises aim to standardize the way they implement network change without disturbing existing systems. That often means using NCCM tools to map and archive the entire network and its ...Continue Reading

• 10 Gigabit Ethernet tutorial: Connecting data centers, storage, LAN and beyond

  As IT teams build 10 Gigabit Ethernet networks, they'll have to choose the right 10 Gigabit Ethernet cabling and components in order to ensure data center optimization and prevent latency in the network. They''ll also need to be sure their networks ...Continue Reading

• 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.Continue Reading

• Metro Ethernet

  Metro Ethernet is the use of Carrier Ethernet technology in metropolitan area networks (MANs)... (Continued)Continue Reading

• 6to4

  6to4 is a tunneling mechanism used to transfer IPv6 (Internet Protocol version 6) packets over an IPv4 infrastructure, typically the IPv4 Internet. The 6to4 mechanism was created to support coexistence of both versions during the transition to IPv6,...Continue Reading

• Choosing WAN connectivity and services wisely

  This guide explores the evolution of the wide area network and the WAN connectivity services being developed to improve remote connections, including the use of services like MPLS, Ethernet, and the Internet.Continue Reading

• WAN performance: More than meeting the need for network speed

  WAN performance and measurement, as well as overall network design and capabilities, are being impacted as enterprises increasingly rely on mobile workforces and remote locations to grow and compete in a global marketplace.Continue Reading

• Citrix Access Gateway

  Access Gateway is a secure application access solution that provides administrators application-level control allowing users application access from anywhere.Continue Reading

• Enterprise wireless LAN security: 802.11 and seamless wireless roaming

  Learn how to secure your enterprise wireless local area network (LAN) in this guide of industry best practices. Wireless networking expert Lisa Phifer explains how network security is improved by the wireless IEEE 802.11n protocol; how to secure ...Continue Reading

• location-based service (LBS)

  A location-based service (LBS) is a software application for a mobile device that requires knowledge about where the mobile device is located.Continue Reading

• NetQoS ReporterAnalyzer 8.1

  NetQoS ReporterAnalyzer, the network traffic analysis module of the NetQoS Performance Center, captures a rich set of traffic statistics from Cisco IOS® NetFlow or other IPFIX-enabled routers and switches to identify which applications and users...Continue Reading

• Citrix Branch Repeater 5

  Citrix Branch Repeater is a branch optimization solution that accelerates application delivery for remote users, reducing bandwidth costs and simplifying infrastructure.Continue Reading

• Modeling can be key to capacity planning

  Planning for the future of your network sometimes requires rigorous planning and modeling. In this tip, Ed Tittel shows how a free modeling tool just may come to your rescue.Continue Reading

• Introduction to IPv6 -- 'IPv6 Security,' Chapter 1

  Learn what the Internet Protocol version 6 (IPv6) is, know who has adopted it, understand the vulnerabilities causing security concerns, and learn methods used to protect networks against hacker attacks and tools.Continue Reading

• How does a firewall work?

  A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks. An enterprise with an intranet that allows its workers access to the wider Internet ...Continue Reading

• 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.Continue Reading

• Seebeck effect

  The Seebeck effect describes the generation of electricity following the connection of two dissimilar electrical conductors or semiconductors that illustrates the thermoelectric effect. Continue Reading

• WAN technologies summarized

  This excerpt from 'The Shortcut Guide to Optimizing WAN Application Delivery' introduces current and existing WAN environments and technologies. Topics include point-to-point links, circuit and packet switching methodologies, virtual circuits, ...Continue Reading

• 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)Continue Reading

• Class of Service (CoS)

  Class of Service (CoS) is a way of managing traffic in a network by grouping similar types of traffic (for example, e-mail, streaming video, voice, large document file transfer) together and treating each type as a class with its own level of ...Continue Reading

• Internet Routing in Space (IRIS)

  Internet Routing in Space in Space, also known as (IRIS), is a project being conducted by the U.S. Department of Defense to place an IP (Internet protocol) router on a geostationary satellite... (Continued)Continue Reading

• Trouble connecting to the VPN: Static and dynamic IP address issues

  For mobile or remote employees, a corporate VPN promises simple, secure access to privileged data and resources. But when that access fails, troubleshooting VPN connectivity issues can be frustrating for the end user and networking staff alike. In ...Continue Reading

• 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...Continue Reading

• Best practices for securing your wireless LAN

  Perhaps the biggest network security concern for many enterprises is securing a wireless local area network (WLAN). This three-part expert lesson provides best practices for securing a WLAN in the enterprise. Lesson 1 focuses on methods of ...Continue Reading

• cognitive radio (CR)

  Cognitive radio (CR) is a form of wireless communication in which a transceiver can intelligently detect which communication channels are in use and which are not, and instantly move into vacant channels while avoiding occupied ones... (Continued)Continue Reading

• 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 ...Continue Reading

• thermoelectric cooling

  Thermoelectric cooling is a way to remove thermal energy from a medium, device or component by applying a voltage of constant polarity to a junction between dissimilar electrical conductors or semiconductors...(continued)Continue Reading

• MDI/MDIX (medium dependent interface/MDI crossover)

  MDI/MDIX is a type of Ethernet port connection using twisted pair cabling.Continue Reading

• FECN/BECN (forward explicit congestion notification/backward explicit congestion notification)

  In a frame relay network, FECN (forward explicit congestion notification) is a header bit transmitted by the source (sending) terminal requesting that the destination (receiving) terminal slow down its requests for data.Continue Reading

• Carrier Sense Multiple Access/Collision Detect (CSMA/CD)

  Carrier Sense Multiple Access/Collision Detect (CSMA/CD) is the protocol for carrier transmission access in Ethernet networks.Continue Reading

• 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

• 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

• 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

• Ethernet Glossary

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

• 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

• 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

• 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 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

• 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 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

• 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

• 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