Glossary F-G

Glossary F-G
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F: Frequency.
FAQ: Frequently Asked Questions
Farad: A unit of capacitance, Usually expressed in microfarads which is one millionth of a farad.
FAS : (Fire Alarm & Signal Cable)
Fast Ethernet: A 100BaseT 802.3u standard, Fast Ethernet merely reduces the "bit time" (duration of each bit transmission) by a factor of ten resulting in 10 times the performance of 10BaseT. Because 100BaseT uses the same CSMA/CD access method used on all Ethernet products, the solution can be deployed into existing networks without requiring massive cabling changes.
Fault: A condition that causes any physical component of a system to fail to perform in an acceptable manner.
Fault Management: 1 of 5 basic network management functions defined by the International Standards Organization (ISO). It involves the detection isolation & correction of fault on the network system.
Fault Tolerance: The ability to operate properly in the even of a failure. These types of systems are designed to ensure that in the event of a power failure, disk crash, or a major user error, data is not lost & the system can continue to operate.
FC: See Frame Control
FCC: See Federal Communications Commission
FCS: See Frame Check Sequence
FDDI: See Fiber Distribution Data Interface
FDM: See Frequency-Division Multiplexor
FDX: See Full Duplex
Federal Communications Commission: (FCC) Government agency that supervises, licenses, & controls standards for all forms of radio & electromagnetic transmissions.
Federal Networking Council: (FNC) A collection of federal agencies that have heavy interests in federal networks using TCP/IP & the Internet. Representatives from DOD, DOE, DARPA, NSF, NASA & HHS are the major members of the FNC.
Feeder Cable: In a CATV system, the transmission cable from the head end (signal pickup) to the trunk amplifier. Also called a trunk cable.
FEP: See Fluorinated Ethylene Propylene or Front End Processor
Ferrous: Composed of and/or containing iron. A ferrous metal exhibits magnetic characteristics.
Fiber: A single. separate optical transmission element characterized by a core & a cladding.
Fiber Distribution Data Interface: (FDDI) Established by American National Standards Institute (ANSI), this standard specifies a data transfer rate of 100 Mbps over fiber & limits network to approximately 200 km in length.
Fiber Loss: The attenuation (deterioration) of the light signal in optical fiber transmission..
Fiber Optics: The transmission of light through optical fibers for communications & signaling.
Field: A group of bits (bytes, words) that typically serves a single function. An example of TCP's sequence number: 32-bit field indicating the number of the first byte of data in a packet.
FIFO: A form of buffer that is used in communication circuits, on a transmitter side, the program writes data into the FIFO while the transmitting circuit reads at a different rate. On a receiving circuit, received data is stored in the FIFO in case the program isn't yet ready to read it.
Figure 8 Cable: An aerial cable configuration in which the conductors & the steel strand which supports the cable are integrally jacketed. A cross section of the finished cable approximates the figure "eight".
File: A collection of related data stored on a disk & treated as a single unit.
File Server: A computer which provides file storage for workstations on the network. The workstations can use the disks on the file server as though they were attached to the workstation. File Transfer Access & Management: See FTAM
File Transfer Access & Management: (FTAM) An application level protocol governing file access.
File Transfer Protocol: (FTP) The application-level protocol used to transfer files between two hosts on a TCP/IP based network system.
Filled Cable: A telephone cable construction in which the cable core is filled with a material that will prevent moisture from entering or passing through the cable.
Fillers: Nonconductive components cabled with the insulated conductors or optical fibers to impart roundness, flexibility, tensile strength, or a combination of all three, to the cable.
Filter: Used in reference to a function performed by a bridge. It involves comparing each packet received with the specification set by the network manager. Packets are forwarded or rejected according to these specifications. Filtering allows a network manager to conduct several tasks including limiting protocol specific traffic to one network segment, isolating electronic mail domains. & performing several other traffic control functions.
Finger: A UNIX command that shows information about a user or group of users on the Internet. The Finger command usually returns the user's real name, whether or not they have unread mail, & the time & date of their last login. Finger also displays two files (if they exist) located in the home directory of the user you fingered. These two files (the .PLAN & the .PROJECT files.) are simply ASCII text files that can be entered by the user to display any information upon being fingered.
Fire Alarm & Signal Cable: (FAS)
Firewall: A term used in reference to the router's ability to contain a fault to the area of the network that it occurs on.
Firmware: A computer program or software stored permanently in PROM or ROM or semi-permanently in EPROM.
Flag: In communications, a bit pattern of six consecutive "1" bits (character representation is 01111110) used in many bit-oriented protocols to mark the beginning (& often the end) of a frame.
Flame: A negative response to an e-mail message or newsgroup posting. The most common recipients of flames are users who post commercial message in public forums, adult material in non-adult areas of the Internet, or racial or gender-biased comments. The worst sort of flame is known as a "mail-bomb," which occurs when the user bearing flamed open his or her e-mail & receives a flood of letters with unusually long file attachments that make his or her computer "crash."
Flame Resistance: The ability of a material not to propagate flame once the heat source is removed.
Flammability: The measure of the material's ability to support combustion.
Flash ROM: Read only memory (ROM) that is electronically reprogrammable & non-volatile (remains in memory when the unit is powered down for normal periods of time).
Flat Cable: A cable with two smooth or corrugated, but essentially flat surfaces.
Flex Life: The ability of a cable to bend many times before breaking.
Flexibility: The ability of a cable to bend in a short radius.
Floating: Referring to a circuit which has no connection to ground.
Flourinated Ethylene Propylene: (FEP) Was formally called X-100 or FEP-100. This "Teflon" FEP fluorocarbon resin in a register trademark of the DuPont de Nemours Co.
Flow Control: Any of several hardware or software techniques used to prevent a source node's transmission from over- running the destination node's capacity to receive & process the information. Flow control can use physical hardware techniques, e.g. dedicated signal lines between a modem & computer, or software techniques, such as windowing information used by a network protocol such as TCP.
FM: See Frequency Modulation
FNC: See Federal Networking Council
Forwarding: Process whereby an Ethernet switch or bridge creates the contents of a packet & then passes that packet on to the appropriate attached segment. A forwarding rate is the time that it takes the device to execute all the steps.
Four-Wire Lines: A telephone line (circuit) between two DTE's using two pairs of wires. One pair is used for sending & the other pair used for receiving signals.
Fragmentation: The process of dividing a datagram into smaller datagrams. Fragmentation is required to transmit large datagrams through network which can only transmit smaller datagrams. The Internet Protocol includes facilities for fragmentation.
Frame: A block of data consisting of its own set of control information, including transmission address & data for error detection.
Frame Check Sequence: (FCS) In bit-oriented protocols, a 16-bit field that contains transmission error-checking information, usually appended at the end of a frame.
Frame Control: (FC) On Token Ring networks, this data supplies the frame type.
Frame Relay: A packet switching concept designed to maximize throughput & minimize costs by simplifying network processing. It is particularly suitable for applications in which the endpoints are intelligent devices & where transmission lines are of high quality.
Frame Switch: A multiport device that receives variable length LAN frames & creates point-to-point connections to deliver a unicast frame to only the output associated with the destination address identified in the LAN frame.
Freenet: A network system made up of community-based bulletin board systems with e-mail, information services, interactive communications, & conferencing. they are usually funded & operated by individuals or organizations much like public television. Freenet providers are part of the National Public Telecomputing Network (NPTN), a Cleveland-based organization that works to make computer networking services as freely available as public libraries.
Frequency: Rate of cycles per second. The unit of measurement is Hertz (Hz): cycles per second.
Frequency Modulation: (FM) A modulation technique. The frequency of the carrier signal is modified to carry the digital information
Frequency Response: The characteristic of a device denoting the range of frequencies over which it may be used effectively.
Frequency Shift Key: (FSK) Frequency modulation of the character which varies between a fixed number of frequencies.
Frequency-Division Multiplexor: (FDM) A device that divides the available transmission frequency range into narrower banks, each of which is used for a separate channel.
Front End Processor: (FEP) A dedicated computer linked to one or more host computers or multi-user minicomputers; performs data communications functions & serves to off-load attached computers of network processing; in IBM SNA networks, an IBM 3704, 3705, 3725 or 3745.
FSK: See Frequency Shift Key
FTAM: See File Transfer Access & Management
FTP: See File Transfer Protocol
Full Duplex: (FDX) Simultaneous two-way communication.
Fusion Splice: A permanent joint accomplished by the application of localized heat sufficient to fuse or melt the ends of optical fiber.
Gain: Increased signal power, usually the result of amplification
Gateway: A device that allows communication between dissimilar LANs by translating information from one to the other (e.g. Ethernet to Token Ring).
Gauge: A term used to denote the physical size of a wire.
GHz: see Gigahertz
Gigahertz: (GHz) A unit of frequency equal to one billion hertz.
GND: See Ground
Gopher: An information search & retrieval tool used widely for research. Gopher information is stored hierarchically on computers across the Internet. It uses a simple protocol that allows a client to access information from a multitude of numerous Gopher servers at one time, creating what's known as "gopher space." The most common search tools in gopher are Veronica & Jughead. Gopher clients exist for most platforms.
GOSIP: See Government OSI Profile
Government OSI Profile: (Government OSI Profile) A version of the OSI (Open Systems Interconnection) model designed specifically for the U.S. government.
Graded-Index Fiber: A type of fiber where the refractive index of the core is lower toward the outside off the fiber. It bends the rays inward & also allows them to travel faster in the lower index of refraction region. This type of fiber provides high bandwidth capabilities.
Ground: (GND) A conducting connection, whether intentional or accidental, between an electrical circuit or equipment & the earth, or to some conducting body that serves in place of the earth.
Ground Loop: A completed circuit between shielded pairs of a multiple pair created by random contact between shields. An undesirable circuit condition in which interference is created by ground currents when grounds are connected at more than one point.
Ground Potential: The potential of the earth, A circuit, terminal, or chassis is said to be at ground potential when it is used as a reference point for other potentials in the system.
Group Addressing: In transmission, the use of an address that is common to two or more stations; on a multiport line, where all stations recognize addressing characters, but only one station responds.

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