Fast Ethernet* - A version of Ethernet which operates at 100 Mbps. See 100Base-Tx and 100Base-FX.

FDDI (Fiber Distributed Data Interface)* - A high-speed networking standard. The underlying medium is fiber optics and the topology is a dual-attached, counter-rotating Token Ring. The FDDI protocol has also been adapted to run over traditional copper wires.

Fiber Channel* - A form of high-speed fiber optic transmission designed primarily for communications between mainframe computers, and between mainframe computers and high-speed peripherals such as disk drives. Sometimes used for general-purpose networking.

Fiber Optic Cable* - A type of cable consisting of glass or plastic fibers that are used to carry light signals. Fiber optic cable supports transmission speeds up into the 100Mbps.

Fiber Optic Transmission* - A communications scheme whereby electrical data is converted to light energy and transmitted through optical fibers.

Flame Resistance - The ability of a material not to propagate flame once the heat source is removed

Flex Life - The measurement of the ability of a conductor to withstand repeated bending.

FOIRL (Fiber Optic Inter Repeater Link)* - A fiber optic signaling method based on the IEEE 802.3 standard governing fiber optics. Allows up to 1,000 meters (3,280 ft.) of multi-mode duplex fiber optic cable in a point-to-point link.

Frame Relay* - An ITU standard for the interface to a public frame-switching network designed to provide high-speed frame transmission with minimum delay across the wide area. It operates at layer two, and is used in public and private networks, gradually replacing X.25 and leased-line networks.

Full-Duplex* - A communications method in which a transmission path is provided in each direction, so that each end can simultaneously transmit and receive.

Gauge - A term used to denote the physical size of a wire.

Gbps* - Billions of bits per second.

Giga - A numerical prefix denoting one billion (109).

Gigabit Ethernet* - A variant of Ethernet which operates over multi-mode fiber optic cable, single mode fiber optic cable, or unshielded twisted pair, at 1,000 Mbps.

Ground - A conducting connection between an electrical circuit and the earth or other large conducting body to serve as an earth thus making complete electrical circuit.

Half-Duplex* - A communications method in which one end transmits while the other receives, then the process is reversed. This was common in wide area point-to-multipoint circuits, such as those used in many SNA networks.Head End -A central point in a broadband network that receives signals on one set of frequency bands and retransmits them on another set of frequencies. The head end is viewed as a central hub. Every transmission on a broadband network must go through the head end.

Hard Drawn Copper Wire - Copper wire that has not been annealed after drawing.

Head End* - A central point in a broadband network that receives signals on one set of frequency bands and retransmits them on another set of frequencies. The head end is viewed as a central hub. Every transmission on a broadband network must go through the head end.

Hi-Pot - A test designed to determine the highest voltage that can be applied to a conductor without breaking through the insulation.

Horizontal Cabling* - That portion of a building's cabling system which extends from the wiring closets to the individual workstations, servers, telephones, and other devices. This is generally copper twisted pair cable.

Hot Swapping* - The process of replacing a module without bringing down the system. This process occurs by sliding an active module into or out of a fully powered unit without shutdown.

Hub* - The center of a star topology network or cabling system. Typically used in older Ethernet and token ring networks. A device connected to a hub receives all the transmissions of all other devices connected to that hub. Hubs are now being replaced in many cases by LAN switches.

Hybrid cable* - An assembly of two or more cables, of the same or different types or categories, covered by one overall sheath.

Hybrid Network* - A LAN consisting of a number of topologies and access methods. For example, a network that includes both token ring and Ethernet.

HZ (Hertz)* - A measure of frequency or bandwidth.

IDC (Insulation Displacement Contact)* - A type of wire terminating connection in which the insulating jacket is cut by the connector when the wire is inserted.

IEEE (Institute of Electrical and Electronic Engineers)* - A standards-making body responsible for implementing many standards used in LANs, including the 802.x series.

IEEE 802.1D* - See "Spanning Tree".

IEEE 802.1p* - An IEEE standard for prioritizing time-critical flows and filtering multicast traffic to contain traffic in layer-two networks. The 802.1 p header includes three bits for prioritization, allowing for eight priorities to be established.

IEEE 802.1Q* - An IEEE standard for providing a virtual LAN capability within a campus network, used in conjunction with IEEE LAN protocols such as Ethernet and token ring.

IEEE 802.2* - A data link standard outlining how basic data connectivity over cable should be set up. Used with the IEEE 802.3, 802.4 and 802.5 standards.

IEEE 802.3* - The IEEE's specification for Ethernet, including both physical cabling and layer-two protocol.

IEEE 802.5* - The IEEE's specification for token ring, including both physical cabling and layer-two protocol.

IEEE 802.10* - The IEEE's protocol for providing security in a metropolitan area network. A variant of 802.10 has sometimes been used to provide a virtual LAN service within a campus network, although this is now generally replaced with 802.1 Q.

IEEE 802.11b* - Insertion Loss is the amount of the signal that is lost (attenuation) as the signal passes through a connection or interface.

Impedance - The total opposition that a circuit offers to the flow of alternating current or any other varying current at a particular frequency. It is a combination of resistance R and reactance X, measured in ohms.

Inductance - The property of a circuit or circuit element that opposes a change in current flow, thus causing current changes to lag behind voltage changes. It is measured in henrys.

Insulation - A material having high resistance to the flow of electric current. Often called a dielectric in radio frequency cable.

Insulation Resistance - The radio of the applied voltage to the total current between two electrodes in contact with a specific insulation, usually expressed in megohms-M feet.

Internetwork* - Two or more networks connected by bridges or routers.

Intranet* - The use of various Internet tools and protocols, especially HTTP and HTML, within an organization.

Jacket - An outer nonmetallic protective covering applied over an insulated wire or cable

Kbps* - Thousands of bits per second.

Ki I o (K) - A numerical prefix denoting 1000 (10³).