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Bring yourself up to speed with our introductory content.

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Bring yourself up to speed with our introductory content.

  • SYN scanning

    SYN scanning is a tactic that a malicious hacker (or cracker) can use to determine the state of a communications port without establishing a full connection. Continue Reading

  • dynamic packet filter

    A dynamic packet filter is a firewall facility that can monitor the state of active connections and use this information to determine which network packets to allow through the firewall. Continue Reading

  • NNTP (Network News Transfer Protocol)

    NNTP (Network News Transfer Protocol) is the predominant protocol used by computer clients and servers for managing the notes posted on Usenet newsgroups. Continue Reading

  • Xmodem

    Xmodem is an error-correcting protocol for modem that was created in 1978 by Ward Christensen and became a de facto standard. Continue Reading

  • 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. Continue Reading

  • encapsulation

    In general, encapsulation is the inclusion of one thing within another thing so that the included thing is not apparent.Continue Reading

  • CCITT or ITU-T (Telecommunication Standardization Sector of the International Telecommunications)

    The CCITT, now known as the ITU-T (for Telecommunication Standardization Sector of the International Telecommunications Union), is the primary international body for fostering cooperative standards for telecommunications equipment and systems.Continue Reading

  • modem error-correcting protocols

    The protocols that modems agree on and use for checking and correcting transmission errors have evolved toward accuracy, speed, and efficiency since 1978 when the Xmodem protocol became a de facto standard.Continue Reading

  • datagram

    A datagram is, to quote the Internet's Request for Comments 1594, "a self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between ...Continue Reading

  • 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.Continue Reading

  • Link Control Protocol (LCP)

    In the Point-to-Point Protocol (PPP), the Link ControlProtocol (LCP) establishes, configures, and tests data-link Internet connections.Continue Reading

  • FG-D (Feature Group D)

    FG-D (Feature Group D) is a type of telecommunication trunk used to provide "equal access" capability from telecommunication carriers and central offices (where the switching equipment is located and customer lines are connected and terminated) to ...Continue Reading

  • WebNFS

    WebNFS is a product and proposed standard protocol from Sun Microsystems that extends its Network File System (NFS) to the Internet.Continue Reading

  • Gigabit Ethernet

    Gigabit Ethernet, a transmission technology based on the Ethernet frame format and protocol used in local area networks (LANs), provides a data rate of 1 billion bits per second (one gigabit). (Continued...)Continue Reading

  • COFDM

    COFDM is a modulation scheme that divides a single digital signal across 1,000 or more signal carriers simultaneously.Continue Reading

  • Ymodem

    Ymodem is an error-correcting protocol for a modem that uses larger data blocks for greater efficiency.Continue Reading

  • SCTP (Stream Control Transmission Protocol)

    SCTP (Stream Control Transmission Protocol) is a protocol for transmitting multiple streams of data at the same time between two end points that have established a connection in a network.Continue Reading

  • EIGRP (Enhanced Interior Gateway Routing Protocol)

    EIGRP (Enhanced Interior Gateway Routing Protocol) is a network protocol that lets routers exchange information more efficiently than with earlier network protocols.Continue Reading

  • 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.Continue Reading

  • 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 ...Continue Reading

  • foreign network

    In the Mobile Internet Protocol (Mobile IP), a foreign network is any network other than the home network to which a mobile device may be connected.Continue Reading

  • 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.Continue Reading

  • sliding windows (windowing)

    Sliding windows, a technique also known as windowing, is used by the Internet's Transmission Control Protocol (TCP) as a method of controlling the flow of packets between two computers or network hosts.Continue Reading

  • foreign agent

    In Mobile Internet Protocol (Mobile IP), a foreign agent is a router serving as a mobility agent for a mobile node.Continue Reading

  • Next Hop Resolution Protocol (NHRP)

    In a computer network, the Next Hop Resolution Protocol (NHRP) is a protocol or method that can be used so that a computer sending data to another computer can learn the most direct route (the fewest number of hops) to the receiving computer.Continue Reading

  • 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.Continue Reading

  • FDDI (Fiber Distributed Data Interface)

    FDDI (Fiber Distributed Data Interface) is a set of ANSI and ISO standards for data transmission on fiber optic lines in a local area network (LAN) that can extend in range up to 200 km (124 miles).Continue Reading

  • NAK (negative acknowledgment or not acknowledged)

    NAK is an abbreviation for negative acknowledgment or not acknowledged.Continue Reading

  • 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)Continue Reading

  • Technical Office Protocol (TOP)

    Technical Office Protocol (TOP), also called Technical and Office Protocol, is a set of protocols intended for networks that perform distributed information processing in business offices... (Continued)Continue Reading

  • FireWire

    FireWire is Apple Computer's version of a standard, IEEE 1394, High Performance Serial Bus, for connecting devices to your personal computer.Continue Reading

  • HomeRF (home radio frequency)

    HomeRF (for home radio frequency) is a home networking standard developed by Proxim Inc.Continue Reading

  • SDLC (Synchronous Data Link Control)

    (SDLC is also an abbreviation for systems development life cycle.Continue Reading

  • Fast Ethernet

    Fast Ethernet is a local area network (LAN) transmission standard that provides a data rate of 100 megabits per second (referred to as "100BASE-T").Continue Reading

  • IPX (Internetwork Packet Exchange)

    IPX (Internetwork Packet Exchange) is a networking protocol from Novell that interconnects networks that use Novell's NetWare clients and servers.Continue Reading

  • spanning tree protocol (STP)

    Spanning tree protocol (STP) is a Layer 2 network protocol used to prevent looping within a network topology. The protocol allows two bridges to exchange information for only one bridge to handle a given message sent between two computers within the...Continue Reading

  • Dynamic Source Routing (DSR)

    Dynamic Source Routing (DSR) is a self-maintaining routing protocol for wireless networks. The protocol can also function with cellular telephone systems and mobile networks with up to about 200 nodes. A Dynamic Source Routing network can configure ...Continue Reading

  • X.25

    The X.25 protocol, adopted as a standard by the Consultative Committee for International Telegraph and Telephone (CCITT), is a commonly-used network protocol.Continue Reading

  • GARP (Generic Attribute Registration Protocol)

    GARP (Generic Attribute Registration Protocol) is a local area network (LAN) protocol that defines procedures by which end stations and switches can register and de-register attributes, such as network identifiers or addresses, with each other...Continue Reading

  • 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.Continue Reading

  • sniffer

    In common industry usage, a sniffer (with lower case "s") is a program that monitors and analyzes network traffic, detecting bottlenecks and problems.Continue Reading

  • NBMA (non-broadcast multiple access)

    NBMA (non-broadcast multiple access) is one of four network types in the OSPF (Open Shortest Path First) communications protocol.Continue Reading

  • Nagle's algorithm

    Named for its creator, John Nagle, the Nagle algorithm is used to automatically concatenate a number of small buffer messages; this process (called nagling) increases the efficiency of a network application system by decreasing the number of packets...Continue Reading

  • 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 ...Continue Reading

  • FCAPS (fault-management, configuration, accounting, performance, and security)

    FCAPS is a network management framework created by the International Organization for Standardization (ISO). FCAPS categorizes the working objectives of network management into five levels. The five levels are:  fault-management (F), the ...Continue Reading

  • connectionless

    In telecommunication, connectionless describes communication between two network end points in which a message can be sent from one end point to another without prior arrangement.Continue Reading

  • circuit-switched

    Circuit-switched is a type of network in which a physical path is obtained for and dedicated to a single connection between two end-points in the network for the duration of the connection.Continue Reading

  • Intelligent Network (IN)

    Intelligent Network (IN) is a telephone network architecture originated by Bell Communications Research (Bellcore) in which the service logic for a call is located separately from the switching facilities, allowing services to be added or changed ...Continue Reading

  • DCE (Distributed Computing Environment)

    In network computing, DCE (Distributed Computing Environment) is an industry-standard software technology for setting up and managing computing and data exchange in a system of distributed computers.Continue Reading

  • duplex

    In telecommunication, duplex communication means that both ends of the communication can send and receive signals at the same time.Continue Reading

  • SDH (Synchronous Digital Hierarchy)

    SDH (Synchronous Digital Hierarchy) is a standard technology for synchronous data transmission on optical media.Continue Reading

  • connection-oriented

    In telecommunications, connection-oriented describes a means of transmitting data in which the devices at the end points use a preliminary protocol to establish an end-to-end connection before any data is sent.Continue Reading

  • 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.Continue Reading

  • 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.Continue Reading

  • IP addressing and subnetting fundamentals

    Our IP addressing and subnetting crash course provides an overview of IP addressing-related topics network engineers need to know, including IPv4 and IPv6, subnetting, DHCP, and calculating subnet masks. For more in-depth information, visit our ...Continue Reading

  • 10BASE-T

    10BASE-T, one of several physical media specified in the IEEE 802.3 standard for Ethernet local area networks (LANs), is ordinary telephone twisted pair wire.Continue Reading

  • 100BASE-T

    In 100 Mbps (megabits per second) Ethernet (known as Fast Ethernet), there are three types of physical wiring that can carry signals: 100BASE-T4 (four pairs of telephone twisted pair wire) 100BASE-TX (two pairs of data grade twisted-pair wire) ...Continue Reading

  • 32-bit IP addressing

    32-bit IP addressing is the IP address scheme used in Internet Protocol 4 (IPv6 uses a 128-bit system)... (Continued)Continue Reading

  • graceful degradation

    Graceful degradation is the ability of a computer, machine, electronic system or network to maintain limited functionality even when a large portion of it has been destroyed or rendered inoperative. The purpose of graceful degradation is to prevent ...Continue Reading

  • bottleneck

    A bottleneck is a stage in a process that causes the entire process to slow down or stop. In a communications context, a bottleneck is a point in the enterprise where the flow of data is impaired or stopped entirely... (Continued)Continue Reading

  • star network

    A star network is a local area network (LAN) in which all nodes (workstations or other devices) are directly connected to a common central computer.Continue Reading

  • Introduction -- Chapter 1 of 'Network Analysis, Architecture and Design'

    This chapter introduces the analysis, architecture, and design processes. Described are the fundamental concepts of the processes of network analysis, architecture, and design; systems and services; as well as their characteristics and prepares the ...Continue Reading

  • wideband

    Wideband is a transmission medium or channel that has a wider bandwidth than one voice channel (with a carrier wave of a certain modulated frequency).Continue Reading

  • E-carrier system

    To see the relationship between the E-carrier system, the T-carrier system, and DS0 multiples, see digital signal X. E1 (or E- is a European digital transmission format devised by the ITU-TS and given the name by the Conference of European Postal ...Continue Reading

  • committed information rate (CIR)

    committed information rateContinue Reading

  • carrier-to-noise ratio (CNR or C/N)

    In communications, the carrier-to-noise ratio, often written CNR or C/N, is a measure of the received carrier strength relative to the strength of the received noise.Continue Reading

  • microwave

    The term microwave refers to electromagnetic energy having a frequency higher than 1 gigahertz (billions of cycles per second), corresponding to wavelength shorter than 30 centimeters.Continue Reading

  • in-band signaling

    In the public switched telephone network, (PSTN), in-band signaling is the exchange of signaling (call control) information on the same channel that the telephone call itself is using.Continue Reading

  • baseband

    Describes a telecommunication system in which information is carried in digital form on a single unmultiplexed signal channel on the transmission medium.Continue Reading

  • band

    In telecommunication, a band - sometimes called a frequency band - is a specific range of frequencies in the radio frequency (RF) spectrum, which is divided among ranges from very low frequencies (vlf) to extremely high frequencies (ehf).Continue Reading

  • broadband voice gateway

    A broadband voice gateway is a device that allows you to make telephone calls over a high-speed Internet connection rather than through a regular telephone outlet without having to go through your computer.Continue Reading

  • ADSL (Asymmetric Digital Subscriber Line)

    Also see Fast Guide to DSL. ADSL (Asymmetric Digital Subscriber Line) is a technology for transmitting digital information at a high bandwidth on existing phone lines to homes and businesses.Continue Reading

  • ARCNET

    ARCNET is a widely-installed local area network (LAN) technology that uses a token-bus scheme for managing line sharing among the workstations and other devices connected on the LAN.Continue Reading

  • CCNA exam preparation guide

    A learning guide for CCNA exam preparation with book chapters, expert advice and quiz.Continue Reading

  • 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 ...Continue Reading

  • V.90

    V.90 is a A Tour of the Internet, Who Runs It, Standards Org, approved by the International Telecommunications Union (ITU-TS), for transmitting data downstream to modems at 56 Kbps (thousand bits per second).Continue Reading

  • spread spectrum

    Spread spectrum is a form of wireless communications in which the frequency of the transmitted signal is deliberately varied.Continue Reading

  • Nessus

    Nessus is an open-source network vulnerability scanner that uses the Common Vulnerabilities and Exposures architecture for easy cross-linking between compliant security tools.Continue Reading

  • 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...)Continue Reading

  • virtual circuit

    A virtual circuit is a circuit or path between points in a network that appears to be a discrete, physical path but is actually a managed pool of circuit resources from which specific circuits are allocated as needed to meet traffic requirements.Continue Reading

  • permanent virtual circuit (PVC)

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

  • Network+ certification: Where does CompTIA Network+ take you? Part 3

    Network+ certification: Where does CompTIA Network+ take you?Continue Reading

  • network access control (NAC)

    Network access control (NAC), also called network admission control, is a method of bolstering the security of a proprietary network by restricting the availability of network resources to endpoint devices that comply with a defined security policy....Continue Reading

  • maximum transmission unit (MTU)

    A maximum transmission unit (MTU) is the largest size packet or frame, specified in octets (eight-bit bytes), that can be sent in a packet- or frame-based network such as the Internet.Continue Reading

  • maximum segment size (MSS)

    The maximum segment size (MSS) is the largest amount of data, specified in bytes, that a computer or communications device can handle in a single, unfragmented piece.Continue Reading

  • network analyzer (protocol analyzer or packet analyzer)

    A network analyzer is a combination of hardware and programming, or in some cases a stand-alone hardware device, that can be installed in a computer or network to enhance protection against malicious activity... (Continued)Continue Reading

  • asymmetric communications

    In telecommunications, the term asymmetric (also asymmetrical or non-symmetrical) refers to any system in which the data speed or quantity differs in one direction as compared with the other direction, averaged over time.Continue Reading

  • anycast

    In Internet Protocol Version 6 (IPv6), anycast is communication between a single sender and the nearest of several receivers in a group. The term exists in contradistinction to multicast, communication between a single sender and multiple receivers...Continue Reading

  • collision

    In a half duplex Ethernet network, a collision is the result of two devices on the same network attempting to transmit data at exactly the same time.Continue Reading

  • wire speed

    Wire speed refers to the rate of data transfer a given telecommunication technology provides at the physical wire level.Continue Reading

  • ACK

    In some digital communication protocols, ACK is the name of a signal that data has been received successfully (for example, with an acceptable number of errors).Continue Reading

  • BOOTP (Bootstrap Protocol)

    BOOTP (Bootstrap Protocol) is a protocol that lets a network user be automatically configured (receive an IP address) and have an operating system booted (initiated) without user involvement.Continue Reading

  • 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 ...Continue Reading

  • 1000BASE-T

    1000BASE-T is Gigabit Ethernet (1 gigabit is 1000 megabits per second) on copper cables, using four pairs of Category 5 unshielded twisted pair to achieve the gigabit data rate.Continue Reading

  • network operations center (NOC)

    A network operations center (NOC) is a place from which administrators supervise, monitor and maintain a telecommunications network.Continue Reading

  • network access server (NAS)

    A network access server (NAS) is a computer server that enables an independent service provider (ISP) to provide connected customers with Internet access.Continue Reading

  • loopback test

    A loopback test is a test in which a signal in sent from a communications device and returned (looped back) to it as a way to determine whether the device is working right or as a way to pin down a failing node in a network.Continue Reading

  • loopback

    In telephone systems, a loopback is a test signal sent to a network destination that is returned as received to the originator. The returned signal may help diagnose a problem.Continue Reading

  • null modem

    A null modem cable allows you to connect your PC to another nearby PC or serial device using its modem protocol.Continue Reading

  • 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...Continue Reading

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