Glossary F-G0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
- F: Frequency.
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
- 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.
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
- FC: See Frame Control
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
- 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
- Fiber Loss: The attenuation (deterioration) of the light
signal in optical fiber transmission..
- Fiber Optics: The transmission
of light through optical fibers for communications &
- 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
- 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.
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
- 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."
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.
Life: The ability of a cable to bend many times before
- Flexibility: The ability of a cable to bend in a short
- Floating: Referring to a circuit which has no connection to
- 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
- FM: See Frequency Modulation
See Federal Networking Council
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
- 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.
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
- 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
- Frequency Response: The characteristic of a device
denoting the range of frequencies over which it may be used
- Frequency Shift Key: (FSK) Frequency
modulation of the character which varies between a fixed number of
- 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
- FSK: See Frequency Shift
- FTAM: See File Transfer Access &
- FTP: See File Transfer
- Full Duplex: (FDX) Simultaneous
- Fusion Splice: A permanent joint accomplished
by the application of localized heat sufficient to fuse or melt the ends of
- Gain: Increased signal power, usually the result of
- 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
- GHz: see Gigahertz
- Gigahertz: (GHz) A unit of frequency equal to one billion
- 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
- 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
- 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
- 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
- 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.