Glossary-F
A Data Communication Historical Series
By bob Pollard
HOME                 INDEX
 
FABRIC:
A Fiber Channel topology with one or more switching devices

FACILITY:

The term ‘facility’ has more than one meaning and, depending on an individual’s age and experience, may be used to indicate a telephone channel, a line, a circuit, a link, a building that houses communication equipment, or part of the equipment located within the building.

See Channel, Line or Circuit

FACILITY LOOPBACK:

A circuit connection process where a received signal is looped back toward the originator of the signal; originators send side is looped back to the originators receiving side of the two wire circuit.

FACSIMILE (FAX):

A form of document communications where the original image is scanned and converted to an electrical signal, and then the electrical signal is converted to a replica of the original image at the receiving terminal. Usually this is accomplished through the use of telephone lines.

FADING:

Normally refers to the gradual loss of a radio or microwave signal.

FAILOVER:

Data is immediately routed to an alternate data path or device in the event of an adapter, cable, channel controller or other device failure.

FAIL SOFT:

A system operational capability to detect component failures and temporarily modify its processing functions in order to prevent irretrievable loss of data or equipment.

FAILURE DOMAIN:

Area in which a failure occurred in a Token Ring, defined by the information contained in a beacon. When a station detects a serious problem with the network, such as a cable failure, it sends a beacon frame that includes the station reporting the failure, its NAUN, and everything in between. A Beacon frame in turn initiates a process called auto-reconfiguration.

FAIR USE:

Fair use is the concept in copyright law that allows some limited copying of copyrighted material in certain circumstances. A complete work may never be copied. The broadest permissions are for educational purposes, such as copying an article from a magazine or a chapter from a book for a class to use. Other more restrictive permitted uses are short excerpts for purposes of news reporting, criticism, and parody.

FALL FORWARD:

A mode of operation where a MODEM changes to a faster speed if line conditions improve after a fallback occurs.

FALLBACK:

1) A data transfer operational mode where a MODEM is forced to function at a speed slower than its rated speed due to unsatisfactory line conditions.

2) Mechanism used by ATM networks when a path selection process does not generate an acceptable path. The fallback mechanism attempts to determine a path by selectively relaxing certain attributes, such as delay, in order to find a path that meets some minimal set of desired attributes.

FALLBACK PROCEDURES:

A system or individual unit predefined manual and/or automatic operation that is initiated when a fault or failure is detected in the system or unit.

FALSE NEGATIVE:

A false negative error occurs when anti-virus software fails to indicate an infected file is truly infected. False negatives are more serious than false positives, although both are undesirable. False negatives are more common because anti-virus software may miss a new or a heavily modified virus.

FALSE POSITIVE:

A false positive error occurs when anti-virus software wrongly claims a virus infects a clean file. False positives usually occur when the string chosen for a given virus signature is also present in another program.

FAN-OUT:

Device that allows multiple devices on a network to communicate using a single network attachment

FANTAIL:

A panel of Input / Output (I/O) connectors that attach to an equipment rack, providing easy access for data connections to a network.

FAQ:

Frequently Asked Questions: A compiled list of previously asked questions and the response (answers) to the questions; could concern anything relative to a subject or the accessed location.

Usually appears in the form of a ‘read-me’ file in a variety of Internet forums. New users are expected to read the FAQ before participating in newsgroups, bulletin boards, video conferences, etc.

FARAD:

A unit of capacitance: When a capacitor is charged with one coulomb, it produces a potential difference of one volt between its terminals.

FAR-END BLOCK ERROR (FEBE)

Status information sent from the near-end terminal (receiving) to the far-end terminal (transmitting) to indicate the presence of a framing error, parity error, OOF, or AIS event at the far end terminal.

FAR END CROSS TALK:

Line interference occurring in the same direction as the signal transmission; would normally be detected at the receiving end.

FARNET:

Federation of American Research NET-works

FAST DUMP/RESTORE (FDR):

A family of mainframe-based backup/restore utilities that use Symmetrix with existing mainframe infrastructures to provide fast, non-disruptive information protection for both mainframe and open systems environments.

FAST ETHERNET:

Any of a number of 100-Mbps Ethernet specifications: Fast Ethernet offers a speed increase 10 times that of the 10BaseT Ethernet specification while preserving such qualities as frame format, MAC mechanisms, and MTU. Such similarities allow the use of existing 10BaseT applications and network management tools on Fast Ethernet networks.

FAST ETHERNET INTERFACE PROCESSOR:

Interface processor on the Cisco 7000 series routers. The FEIP supports up to two 100-Mbps 100BaseT ports.

FAST INFECTOR:

Fast infector viruses, when active in memory, infect not only executed programs, but also those that are merely opened. Thus running an application, such as anti-virus software, which opens many programs but does not execute them, can result in all programs becoming infected.

FAST PACKET:

A general term for various packet switched technologies including frame relay, Broadband Integrated Services Digital Network (BISDN), and asynchronous transfer mode (ATM). Compared to X.25 packet switching, fast packet has a reduced capability. But, because of lower overhead, fast packet systems can operate at higher rates for the same processing cost.

FAST PACKET SWITCHING:

A packet-oriented digital technology that transmits all data in single packet formats whether the information is video, voice or data. Fast packet switching uses short, fixed length packets and is capable of speeds between 100,000 and 1,000,000 packets per second.

FAST SEQUENCED TRANSPORT (FST):

Connectionless sequenced transport protocol that runs on top of the IP protocol. SRB traffic is encapsulated inside IP data-grams and is passed over an FST connection between two network devices, such as routers. Speeds up data delivery, reduces overhead, and improves the response time of SRB traffic.

FAST SERIAL INTERFACE PROCESSOR:

Default serial interface processor for Cisco 7000 series routers. The FSIP provides four or eight high-speed serial ports.

FAST SWITCHING:

A Cisco feature where a route cache is used to expedite packet switching through a router

FAST SELECT:

A packet-switching function where the user can transmit small amounts of data (approx. 128 characters) with the call request packet, rather than transmitting the data information in packets following the call request packet.

FAT:

File Allocation Table: Under MS-DOS, Windows 3.x, 9.x and NT (some cases), the FAT is located in the boot sector of the disk and stores the addresses of all the files contained on a disk. Viruses and other malicious programs, as well and normal use and extended wear and tear, can damage the FAT. If the FAT is damaged or corrupt, the operating system may be unable to locate files on the disk. See File Allocation Table

FAT32:

A derivative of the File Allocation Table (FAT) file system: FAT32 supports smaller cluster sizes and larger volumes than FAT, which results in more efficient space allocation on FAT32 volumes.

FAULT:

Any condition that causes a device or circuit to fail to operate in a proper manner

FAULT DICTIONARY:

A fault dictionary is a table containing information about all the possible failure modes that computer components and devices can experience. The fault dictionary is used in conjunction with computer diagnostic programs. Diagnostics look up fault signatures stored in the dictionary, and then relate the entry information to a physical location of the failed component. This information can be provided externally to the technician, in a coded format, which allows the technician to manually look up the possible repair information. Or, the diagnostic can translate the dictionary entry to a physical location, which the technician uses to locate the failed component.

FAULT MANAGEMENT:

Refers to one of five categories of network management, as defined by ISO, for management of OSI networks; fault management attempts to ensure that network faults are detected and controlled.

FAULT SIGNATURES:

Fault signatures are stored in a ‘Fault Dictionary’. When diagnostic programmers design hardware diagnostics for computers and devices, they often use a method of physically inducing hardware faults in the circuitry to simulate various failure modes. They do this by taping circuit card pins, strapping disabling voltages to various element points, etc. Each time the programmer examines the response from the logic circuitry and stores the information as a Fault Signature into the dictionary. In this way, the programmer builds up a series of various response patterns called ‘Fault Signatures’.

FAULT TOLERANCE:

The ability for a computer or network system to continue operating when software errors or hardware malfunctions occur; a computer or operating systems ability to respond to a catastrophic event like a power outage or hardware failure without loss or corruption of data.

FAULT TOLERANT:

System design features that make a computer or network system resistant to software errors and hardware problems; A fault-tolerant local area network (LAN) system is designed to ensure that in the event of a power failure, a disk crash, or a major user error, data isn't lost and the system continues to function. Cabling systems can also be fault tolerant, using redundant wiring to keep the system functioning, even if a cable is cut.

FAULT TOLERANT SERVER:

A dedicated PC (Personal Computer) that safeguards critical data, and maintains user productivity, through data duplication and backup devices, in the event of a failure on the network.

FAX:

See Facsimile

FAX SERVICE:

A system service that provides fax services to local and remote network clients. Fax services include receiving and sending fax documents, fax wizard messages, and e-mail messages.

FBC:

Facilities-Based Carrier: A carrier that uses its own facilities to provide service. This is in contrast to re-sellers that purchase the services/facilities from other carriers and then retail the services/facilities to their customers.

FBE:

See Framing Bit Error

FCC:

Federal Communications Commission: A board of seven presidential appointees empowered to regulate all USA interstate communications systems as well as all overseas communications originating or terminating in the USA. The FCC was created by the Communications Act of 1934.

FCFS:

First Come First Served

FCS:

Frame Check Sequence: Extra characters added to a frame for error control purposes. Used in HDLC, Frame Relay, and other data link layer protocols.

FDD:

Floppy Disk Drive

FDDI:

Fiber-Distributed Data Interface: LAN standard, defined by ANSI X3T9.5, specifying a 100-Mbps token-passing network using fiber-optic cable, with transmission distances of up to 2 km. FDDI uses dual-ring architecture to provide redundancy.

FDDI II:

ANSI standard that enhances FDDI: FDDI II provides isochronous transmission for connectionless data circuits and connection-oriented voice and video circuits.

FDDI INTERFACE PROCESSOR (FIP):

Interface processor within the Cisco 7000 series routers: The FIP supports SAS(s), DAS(s), dual homing, and optical bypass, and contains a 16-mips processor for high-speed (100-Mbps) interface rates. The FIP complies with ANSI and ISO FDDI standards.

FDDI-TALK:

Apple Computer data-link product that allows an AppleTalk network to be connected by FDDI cable

FDISK /MBR:

If you have MS-DOS version 5.0 or later, the command FDISK /MBR can remove viruses which infect the master boot sector but do not encrypt it. Although using this command can produce unexpected results and cause unrecoverable damage.

FDL:

Facility Data Link: A 4-kbps channel provided by the Extended Super-frame (ESF) T1 framing format. The FDL performs outside the payload capacity and allows a service provider to check error statistics on terminating equipment without main stream intrusion.

FDM:

Frequency Division Multiplexing: A technique used by a multiplexer to allow shared use of a single channel (voice channel) based on differences in assigned frequency.

FDMA:

Frequency Division Multiplexing Access: FDMA separates the frequency spectrum into distinct voice channels by splitting it into uniform chunks of bandwidth. To better understand FDMA, think of radio stations: Each station sends its signal at a different frequency within the available band. FDMA is used mainly for analog transmission. While it is certainly capable of carrying digital information, FDMA is not considered to be an efficient method for digital transmission.

FDX:

Full Duplex: The capability to transmit data in both directions simultaneously. FDX normally uses a four wire circuit, but under certain controls (conditions) may only require a two wire circuit. See four wire equivalent circuits.

FE:

1) Format Effectors: A control character(s) that controls the information (format) displayed on a monitor or printer.

2) Fast Ethernet

FEATURE BOARDS:

Modular system cards that perform specific functionality: For example: DSC or MODEM cards.

FEATURE GROUP A (FGA); B (FGB); C (FGC); D (FGD):

Refers to various switching and termination functions within telephone switching systems

FEBE:

See Far-End Block Error

FEC:

Forward Error Correction: A mathematical technique in which a constant polynomial (syndrome) is applied and transmitted with the data. At the receive location, processing of the data, along with the known polynomial, will allow correction of errors caused by the transmission system.

FECN:

See Forward Explicit Congestion Notification

FEDERAL COMMUNICATIONS COMMISSION:

See FCC

FEDERAL INFORMATION PROCESSING STANDARD:

See FIP

FEED HOLES:

A series of holes in paper tape, inserted by the tape punch, which engage with a sprocket that permits movement of the tape for reading.

FEEDBACK:

1) That part of an output signal (transmitted data) that is returned to the input side of a device.

2) A message sent by a user to System Operations concerning a previous message transmission.

FEIP:

Fast Ethernet Interface Processor: Interface processor on the Cisco 7000 series routers. The FEIP supports up to two 100-Mbps 100BaseT ports.

FEP:

1) Front End Processor (Communications Processor): A computer connected between a general-purpose processor and the communications channels (lines). This allows communications and general-purpose functions to be performed more efficiently than would be possible if the general-purpose processor performed both communications functions and general-purpose functions.

2) Device or board that provides network interface capabilities for a networked device. Example: In SNA, an IBM 3745 device.

FEX, FX:

Foreign Exchange Service: A telephone connection service where the subscriber's telephone is connected to a remote exchange, but it appears to be local telephone service.

FF:

Form Feed: A control character; causes a printer to advance to the top of the next page or form.

FFR:

Force Furlough Reduction: The process of reducing the labor force due to inadequate work force requirements.

FGD:

Feature Group-D: Identifies a standardized service available to carriers delivered on a T1 line.

FGD-EANA:

Feature Group-D: Signaling protocol of Exchange Access North American (EANA). This provides certain call services, such as emergency (USA-911) calls.

FIBER CHANNEL (FC):

Fiber channel is nominally a one-gigabit-per-second data transfer interface technology, although the specification allows data transfer rates from 133 megabits per second up to 4.25 gigabits per second. Data can be transmitted and received at one-gigabit-per-second simultaneously. Common transport protocols, such as Internet Protocol (IP) and Small Computer System Interface (SCSI), run over Fiber Channel. Consequently, high-speed I/O and networking can stem from a single connectivity technology.

FIBER CHANNEL ARBITRATED - LOOP (FC-AL):

FC-AL places up to 126 devices on a loop to share bandwidth. Typically, this is done using a star layout that is logically a loop, employing a Fiber Channel hub. This allows IT managers to add or remove devices without having to bring the entire loop down.

FIBER DISTRIBUTED DATA INTERFACE (FDDI):

An American National Standards Institute (ANSI) standard for high-speed (100 Mbps) Local Area Network (LAN) communications using fiber-optic cable: A dual ring or dual ring of tree topology and a token passing media access method is used. Up to 1000 stations can be connected and can be situated up to 3 kilometers between stations.

FIBER LOSS:

The weakening of light signal strength in fiber optic transmission

FIBER OPTIC COMMUNICATION:

The technology of using light as a means of communication: The signal is transmitted through a medium of optical fiber.

FIBER OPTICS / CABLE:

A fiber optic media is a cable (coaxial cable) made of glass about the diameter of a human hair. It is made from ultra-pure silica glass, which is nearly 200,000 times more pure than ordinary window glass. It is capable of carrying light. That requires the communications to take place in a digital format, either the light is on (a value of 1) or it is off (a value of 0). Transmission occurs at the speed of light (186,000 miles per second).

FIBER OPTICS HISTORY:

   The first fiber optic cables most people saw was in decorative lamps sold at stores. They were typically on the same shelf as lava lamps. A group of fibers were tied together at one end and splayed out in a fan at the other. A bulb at the tied end illuminated them, and the light emerging from the loose ends made them glitter. Still around today!

   It was not until 1977 that, GTE and then AT&T implemented fiber optic cables into telephone circuits carrying live traffic. Though the technology was primitive by the standards of today, for the most part the cable worked flawlessly. Today, telephone companies are installing the fourth generation of fiber optics.

FIBER-OPTIC WAVE-GUIDES:

Thin filaments of glass or other transparent materials through which light beams can be transmitted long distances.

FIBER PLANT:

Aerial or buried fiber optic cable and associated equipment that allows connectivity between users of fiber optic transmission services

FIBREALLIANCE:

Fiber-Alliance is an open association of industry Fiber Channel vendors committed to accelerating the adoption rate of Storage Area Networks (SAN). Members are working to develop a framework specification within which multiple vendors can develop integrated management environments for enterprise SAN customers.

FICON:

Fiber Connectivity: FICON channels provide 100-Mbps bi-directional link rates at unrepeated distances of up to 20 km over fiber optic cables.

FID0:

Format Indicator 0: One of several formats usable by a SNA TH. A FID0 TH is used for communication between a SNA node and a non-SNA node.

FID1:

Format Indicator 1: One of several formats usable by a SNA TH. A FID1 TH encapsulates messages between two sub-area nodes that do not support virtual and explicit routes.

FID2:

Format Indicator 2: One of several formats usable by a SNA TH. A FID2 TH is used for transferring messages between a sub-area node and a PU 2, using local addresses.

FID3:

Format Indicator 3: One of several formats usable by a SNA TH. A FID3 TH is used for transferring messages between a sub-area node and a PU 1, using local addresses.

FID4:

Format Indicator 4:  One of several formats usable by a SNA TH. A FID4 TH encapsulates messages between two sub-area nodes that are capable of supporting virtual and explicit routes.

FIDONET:

A public network connecting thousands of BBS systems around the world.

FIELD:

A group of characters, header, address field, a component of a data base record, etc.

FIELDATA:

1) The U. S. Military code: Used in data processing as a compromise between conflicting commercial codes. This code was compatible with IBM punched cards; early (Compound terminal) data code set used in AUTODIN.

2) The original cross-referenced data code is an IBM developed code for transmitting Hollerith code across communication circuits. In the punched card world, Hollerith, from Herman Hollerith its developer is the code used for the so-called IBM card. It has 80 columns for characters / symbols and 12 rows. The numbers are designated by single punches in the 0-9 positions, the letters and symbols by combinations of the 0-9 and 11-12 positions. But 12 positions do not transmit well, so Fieldata, an 8-bit code, was used for transmission. Extended Fieldata, a larger code set was used for internal and trunk (inter-Center) transmission.

FIELD REPLACEABLE UNIT:

A hardware component that can be removed and replaced on-site: Typical field-replaceable units include electronic cards, power supplies, and chassis components.

FIFO / FIFO QUEUING:

1) ‘First-In, First-Out’; System Linking or Queuing of messages for output is done in such a manner that ensures messages will be delivered, by precedence, on a first-in, first-out basis.

2) FIFO queuing in Packet switching: Buffering and forwarding of packets is processed in the order of arrival. FIFO embodies no concept of priority or classes of traffic. There is only one queue, and all packets are treated equally. Packets are sent out an interface in the order in which they arrive.

FIGURES SHIFT:

1) A control character in Baudot code indicating that subsequent characters are uppercase.

2) A physical shift (uppercase) in a teletypewriter that enables the printing of numbers, symbols, and characters. A ‘Letters shift’ returns the device to lower case alpha characters.

FILE

A complete, named collection of information, such as a program, a set of data used by a program, or a user-created document. A file is the basic unit of storage that enables a computer to distinguish one set of information from another. It is a collection of data that a user can retrieve, change, delete, save, or send to an output device, such as a printer or e-mail program.

FILE ALLOCATION TABLE (FAT):

A file system used by MS-DOS and other Windows based operating systems to organize and manage files. The file Allocation Table is a data structure that Windows creates when a user formats a volume by using the FAT or FAT32 file systems. Windows stores information about each file in the FAT so that it can be retrieved later.

FILE GAP:

Refers to an interval of space or time associated with a file to indicate the end of a file

FILE NAME EXTENSION:

File name extensions follow the period in a file name and indicate the type of information stored in a file. For example, in the file name Example.txt, the file name extension is .txt, which indicates that the file is a text file.

FILE SERVER, FILE SERVER PROTOCOL:

Example: A Local Area Network (LAN) protocol that allows application programs to store and share data files.

FILE SYSTEM:

In an operating system, the overall structure in which files are named, stored, and organized. NTFS, FAT, and FAT32 are types of file systems.

FILE TRANSFER:

Refers to network applications that allow files to be moved from one network device to another

FILE TRANSFER PROTOCOL (FTP):

A member of the TCP/IP (Transmission Control Protocol/Internet Protocol) suite of protocols, used to copy files between two computers on the Internet. Both computers must support their respective FTP roles: one must be an FTP client and the other an FTP server.

FILE TYPE:

In the Windows environment, a designation for the operational or structural characteristics of a file: The file type identifies the program, such as Microsoft Word, that is used to open the file. File types are associated with a file name extension. For example, files that have the .txt or .log extension are of the Text Document type and can be opened using any text editor.

In the Macintosh environment, a four-character sequence that identifies the type of a Macintosh file. The Macintosh Finder uses the file type and file creator to determine the appropriate desktop icon for that file.

FILE VIRUSES:

File viruses usually replace or attach themselves to COM and EXE files. They can also infect files with the extensions SYS, DRV, BIN, OVL and OVY. File viruses may be resident or non-resident; the most common being resident or TSR (Terminate-and-Stay-Resident) viruses. Many non-resident viruses simply infect one or more files whenever an infected file runs.

FILTER:

1) Generally, a process or a device that screens network traffic for certain characteristics, such as source address, destination address, or protocol, and determines whether to forward or discard that traffic based on the established criteria.

2) An electronic device which allows only the specified frequencies to pass or be transmitted/received; all other frequencies are attenuated or deleted.

FILTER-KEYS:

A keyboard feature that causes the keyboard to ignore brief or repeated rapid keystrokes:

Some keyboards rely on switches that that make a direct contact or cause a change in the current flowing through the circuits in the keyboard. When the key is pressed against the switch circuit, there is usually a small amount of vibration between the surfaces, known as bounce. The processor in a keyboard recognizes that this very rapid switching on and off is not caused by pressing the key repeatedly. A user can also adjust the keyboard repeat rate, which is the rate at which a key repeats when it is held down.

FILTERING ROUTER:

Inter-network router that selectively prevents the passage of data packets according to a security policy.

FINGER:

1) Software tool for determining whether a person has an account at a particular Internet site: Many sites do not allow incoming finger requests.

2) An Internet software tool for locating people at other Internet sites: Finger is sometimes used to give access to non-personal information, but the most common use is to see if a person has an account at a particular Internet site. Many sites do not allow incoming Finger requests.

FIP:

FDDI Interface Processor: A processor within the Cisco 7000 series routers: The FIP supports SAS(s), DAS(s), dual homing, and optical bypass, and contains a 16-mips processor for high-speed (100-Mbps) interface rates. The FIP complies with ANSI and ISO FDDI standards.

FIPS:

Federal Information Processing Standard: A US government computer processing and data communications standard.

FIREWALL:

   A combination of hardware and software that provides a security system: Usually to prevent unauthorized access to an internal network or intranet from the outside. A firewall prevents direct communication between network and external computers by routing communication through a proxy server outside of the network. The proxy server determines whether it is safe to let a file pass through to the network. A firewall is also called a security-edge gateway. This feature is also available for the individual users Personal Computer.

   A software and/or hardware based security system designed to protect an organization's Local Area Network (LAN) based computers and servers or individual Personal Computers (PC) against external unauthorized users such as ‘hackers’.  A Firewall can be programmed to filter out certain access categories and keep unwanted users (hackers) on the Internet from accessing computers on the LAN, or a PC, or from maliciously accessing a web server. A Firewall (acting as a proxy server) can also filter out certain categories of accesses to the Internet from users connected to an organization's LAN.

FIRMWARE:

A term used to identify software (instructions) that is permanently / semi- permanently stored in a Read Only Memory (ROM), Programmable Read Only Memory (PROM), Electrically Erasable Programmable Read Only Memory (EEPROM) or Erasable Programmable Read Only Memory (EPROM) chip; requires special equipment to re-program.

FISU:

Fill-In Signal Unit: SS7 message that is sent in both directions whenever other signal units are not present; provides a CRC checksum for use by both endpoints.

FIX:

Federal Internet Exchange: Connection point between North American governmental internet and the Internet. The FIX(s) are named after their geographic region, as in FIX West (Mountain View, California) and FIX East (College Park, Maryland).

FIXED LOSS LOOP (FLL):

A Federal Communications Commission (FCC) requirement: Limits the output of a programmable MODEM to 4 db.

FLAG:

The term ‘flag’ is sometimes used to reference a single bit indicating the presence or absence of a condition. In data transmission, it would be an indicator of an expected event like the beginning or end of a block of data. In CCITT standards for X.25 networks, the 8-bit character 01111110 has been uniquely established with the name ‘Flag’ to be used at the beginning and end of a block.

FLAME (FLAMAGE):

Originally, ‘flame’ meant to carry forth in a passionate manner in the spirit of honorable debate. Flames most often involved the use of flowery language. Recently flame has come to refer to any kind of derogatory comment no matter how witless or crude.

FLAME WAR:

Refers to an online discussion that degenerates into a series of personal attacks against individuals rather than discussion of their positions; a heated exchange.

FLAPPING:

Routing problem where a route between two nodes alternates (flaps) back and forth between two paths due to a network problem that causes intermittent interface failures.

FLASH MEMORY:

A special type of EEPROM that can be erased and reprogrammed: Many modern PCs have their BIOS stored on a flash memory chip so that it can be easily updated if necessary. Flash memory is also popular in MODEM(s) because it enables the MODEM manufacturer to support new protocols as they become standardized.

FLASH UPDATE:

Routing update sent asynchronously in response to a change in the network topology.

FLAT ADDRESSING:

Scheme of addressing that does not use a logical hierarchy to determine location. For example, MAC addresses are flat, so bridging protocols must flood packets throughout the network to deliver the packet to the appropriate location.

FLAT RATE SERVICE:

A fixed rate telephone service: Entitles the subscriber to an unlimited number of calls within a specified area.

FLEXIBLE ARCHITECTURE:

A technical approach designed to blend Organizational (Naval Messages) and Individual (E-mail) messaging users into a single message system using compatible and compliant technical components.

F-LINK:

SS7 Fully associated Link: An SS7 signaling link directly associated with a link carrying traffic, although not necessarily imbedded within the same physical span.

FLIP-FLOP:

A solid state bi-stable device that is capable of assuming either of two stable states. See Boolean algebra

FLOODING:

1) Traffic passing technique used by switches and bridges in which traffic received on an interface is sent out on all the connected interfaces except the interface on which the information was originally received.

2) A process in which a bridge broadcasts a packet it received with an unknown destination address to all local area network (LAN) locations. When it receives a reply from the remote device, it updates its routing table.

FLOPPY DISK:

A reusable magnetic storage medium: The floppy disk used today is the rigid 3.5-inch microfloppy that holds 1.44 MB. It is called a floppy because the first varieties were housed in bendable jackets.

FLOW:

Stream of data traveling between two endpoints across a network: Such as one LAN station to another. Multiple flows can be transmitted on a single circuit.

FLOWCHART:

‘Flowcharting’: A method of diagramming (representing) the steps in solving a problem. The special symbols used in flowcharting correspond to the standards of the International Organization for Standardization. Flowcharts are used to guide the writing (coding) of program instruction sequences.

FLOW CONTROL:

A method of controlling when information is or is not sent, such as ensuring that a transmitting entity, such as a MODEM, does not overwhelm a receiving entity with data. When the buffers on the receiving device are full, a message is sent to the sending device to suspend transmission until the data in the buffers has been processed.

FLOWSPEC:

In IP version 6 (IPv6), the traffic parameters of a stream of IP packets between two applications

FLT:

Full Line Terminal: Multiplexer that terminates a SONET span.

FM:

Frequency Modulation: The carrier (base) frequency is changed to different frequency values based on the data signal. The data signal modulates (modifies) the carrier frequency.

FNC:

Federal Networking Council: A United States group responsible for assessing and coordinating U.S. federal agencies networking policies and needs, especially those networks using TCP/IP, and the Internet.

FOIRL:

Fiber-Optic Inter-Repeater Link: Fiber-optic signaling standard based on the IEEE 802.3 fiber-optic specification. FOIRL is a precursor of the 10BaseFL specification, which is a FOIRL replacement. It is commonly used to support Ethernet backbones.

FOLDER:

A container for programs and files in graphical user interfaces, and can be symbolized on the screen by a graphical image (icon) of a file folder. A folder is a means of organizing programs and documents on a disk and can hold both files and additional folders.

FOLLOW-ME ROAMING:

The ability of a wireless system to forward incoming calls to a cellular handset that is roaming outside the home service area without any pre-notification to the wireless carrier.

FONT:

A graphic design applied to a collection of numbers, symbols, and characters. A font describes a certain typeface, along with other qualities such as size, spacing, and pitch.

FONT CARTRIDGE:

A plug-in unit available for some printers that contains fonts in several styles and sizes: Printers using font cartridges can produce characters in sizes and styles other than those created by the fonts built into It or downloaded from a program.

FOOTPRINT:

Geographical area in which an entity is licensed to broadcast its signal

FOREIGN ATTACHMENT:

Normally refers to equipment attached to the telephone company lines, but not owned or provided by the Telephone Company.

FOREIGN EXCHANGE:

See FEX.

FOREIGN EXCHANGE SERVICE:

See FEX.

FOREGROUND PROCESSING:

High priority processing, usually real time entries (interrupts), given precedence over background processing.

FORM FEED:

See FF

FORMAT:

Refers to an agreed standard for a system where all messages information and/or transmitted data will have identical positioning, information, headers, control fields and control characters (bits), to allow for standardized software, hardware and user preparation.

FORMAT EFFECTORS:

See FE

FORMAT ERRORS:

A reference to any formats deviation from the prescribed format of the signal (data transmission). This includes bipolar violations, low average pulse density, or loss of synchronization.

FORTEZZA:

A crypto card for unclassified, but sensitive information - It also provides integrity and authentication security services.

FORTRAN:

Formula Translation: A high level programming language originally developed to aid mathematicians and engineers in problem solving. The arithmetic statements resemble algebraic statements.

FORWARD CHANNEL:

Communications path carrying information from the call initiator to the called party

FORWARD DELAY INTERVAL:

Amount of time an interface spends listening for topology change information after that interface is activated for bridging and before forwarding actually begins.

FORWARD ERROR CORRECTION:

See FEC.

FORWARD EXPLICIT CONGESTION NOTIFICATION (FECN):

A bit in the frame relay header indicating the frame has passed through a node experiencing congestion in the same direction the frame is traveling.

FORWARDING:

Process of sending a frame toward its ultimate destination by way of an internetworking device

FOT:

Fiber-Optic Terminal: A device that connects copper wire to optical fiber

FOTS:

Fiber Optic Transmission System: With its minimal transit time delay and normally very low bit error rate, FOTS is a superior method for transmitting high-speed data, digital video signals and other compressed signals.

FOUR-OUT-OF-EIGHT CODE:

A communication code used for error detection where four of the eight character bits are always one bits (marking).

FOUR WIRE CIRCUITS (FOUR WIRE CHANNELS):

Circuits using two separate transmission paths of two wires each or their virtual equivalent, for simultaneous two-way (Full Duplex) transmission, as opposed to regular local lines which usually only have two wires to carry conversations in both directions. One set of wires carries information in one direction, the other in the opposite direction.

FOUR WIRE EQUIVALENT CIRCUIT/LINE:

A term used to identify a full duplex operation on a two-wire circuit (pair). The transmitting and receiving channels are separated on the circuit through the use of different carrier (base) frequencies for the two channels.

FOURIER TRANSFORM:

Technique used to evaluate the importance of various frequency cycles in a time series pattern.

FOX MESSAGE:

Test Message/Pattern: A maintenance test pattern or message repeated continuously for problem isolation. Example: "The quick brown fox jumped over the lazy dogs back”. This test message uses all the alpha characters. Numbers can be added to test all the numbers.

FP:

Full Period: A monthly private line service that is rented for the exclusive use of a single customer.

FPS:

See Frames per Second

FQDN:

Fully Qualified Domain Name: FQDN is the full name of a system, rather than just its host name. For example: autodin is a host name, and autodin.interop.com is an FQDN.

FR:

Frame Relay: A wide-band (64 Kbps to 1.544 Mbps) high-speed packet-based data switching interface standard that transmits bursts of data over wide area networks (WANs). Frame-relay packets vary in length from 7 to 1024 bytes.

FRAD:

1) Frame Relay Access Device: Any network device that provides a connection between a LAN and a Frame Relay WAN.

2) See Frame Relay Assembler / Disassemble(r)

FRAGMENT:

Piece of a larger packet that has been broken down to smaller units

FRAGMENTATION:

1) Process of breaking a packet into smaller units when transmitting over a network that cannot support the original size of the packet

2) The scattering of parts of the same disk file over different areas of the disk. Fragmentation occurs as files on a disk are deleted and new files are added. It slows disk access and degrades the overall performance of disk operations.

FRAME:

1) In digital communications, a group of bits or characters sent serially over a channel; generally a logical unit of information between data link layer entities that contains its own control information for addressing and error checking. Synonymous with the term ‘block’ frame (framing).

2) The overhead control characters used to surround the data in an information or text frame.

3) On a T-1 circuit, a frame refers to the 24 bytes plus one framing bit (a total of 193 bits).

4) The sequence of bits and bytes in a transmitted block.

5) A work structure upon which wires can be run to interconnect different devices; typically called a distributing frame or distribution frame.

FRAME CHECK SEQUENCE (FCS):

A 32-bit cyclic redundancy check (CRC) inserted as a field in a block of data to be transmitted. The receiver uses a matching calculation (FCS) to determine validity of a data packet or frame.

FRAME ERROR:

(DS1) Frame synchronization bit error, which occurs in either a terminal framing bit or signaling framing bit of the super-framed format. - (DS3) frame synchronization bit error detected in either the multi-frame alignment signal (M-bit) or frame alignment signal (F-bit).

FRAME FORWARDING:

Mechanism by which frame-based traffic, such as HDLC and SDLC, is processed over an ATM network

FRAME RELAY:

1) Industry-standard, switched data link layer protocol that handles multiple virtual circuits using HDLC encapsulation between connected devices. Frame Relay is more efficient than X.25, the protocol for which it generally is considered a replacement.

2) A packet technology initially defined as an ISDN frame mode service. Frame Relay uses a minimal set of Data Link Layer procedures across the User-to-Network Interface (UNI), which provides unacknowledged transfer of variable length frames between users. Additional Layer 2 and 3 functions must be provided by the end-users. The Layer 2 protocol uses LAPF-Core procedures. The network discards any frame with bit errors.

FRAME RELAY ACCESS SUPPORT (FRAS):

Cisco IOS feature that allows SDLC, Token Ring, Ethernet, and Frame Relay-attached IBM devices to connect to other IBM devices across a Frame Relay network.

FRAME RELAY ASSEMBLER/DIS-ASSEMBLER (FRAD):

A device that is used to interface a customer's local area network (LAN) with the frame relay wide area network (WAN). This device also interfaces a local management interface (LMI) with an Internet packet exchange (IPX) switch port.

FRAME RELAY BRIDGING:

A bridging technique, described in RFC 1490, that uses the same spanning-tree algorithm as other bridging functions, but allows packets to be encapsulated for transmission across a Frame Relay network.

FRAME RELAY FORUM:

A consortium of vendors and consumers, that develop implementation agreements to ensure interoperability between multiple vendors, products and services for frame relay equipment.

FRAME RELAY FRAME:

A variable length unit of data in frame-relay format that is transmitted through a frame relay network; contrast with packet.

FRAME RELAY NETWORK:

A telecommunications network based on frame relay technology; data are multiplexed. Contrast with packet-switching network.

FRAME SLIP:

Any timing shift that occurs on a circuit during frame transmission

FRAME SYNCHRONOUS LOSS:

Examples: In SF, once in sync, when two of the last five framing bits (Ft) are in error. In ESF, once in sync, when two of the last five framing pattern sequence bits are in error.

FRAME TYPES:

  • Information frame (I-frame)
  • Supervisory frame (S-frame)
  • Unnumbered frame (U-frame)
  • Unnumbered Information frame (UI-frame)

FRAMES PER SECOND (FPS):

Examples: Film is 24 FPS, NTSC is 30 FPS and PAL/SECAM is 25 FPS.

FRAMING:

A data framing control procedure: Used in digital transmission and allows the receiver to synchronize with the received data. Framing bits may also carry alarm and control messages in entities like T-1 carrier systems. This makes framing bits in communications carrier systems similar to control characters in data communications.

FRAMING BIT:

A bit introduced into a bit stream that identifies where one frame ends and the next one begins. This bit helps separate the characters at the receiving end of a transmission.

FRAMING BIT ERROR (FBE):

Examples: In SF, the receipt of a terminal frame bit (Ft) or the signal frame bit (Fs) is different than expected. In ESF, the receipt of a framing pattern sequence bit is different than expected.

FRAMING BIT ERROR RATIO:

The number of framing bits in error divided by the total number of framing bits; this computation does not include any period (second) where there is LOS, SES, OOF, or AIS conditions.

FRAS:

See Frame Relay Access Support

FRASM:

Frame Relay access service module.

FREENET:

Community-based bulletin board system with e-mail, information services, interactive communications, and conferencing, and a single point of free access to public information.

FREE-TRADE ZONE:

Part of an AppleTalk inter-network that is accessible by two other parts of the inter-network that cannot directly access each other

FREEWARE:

Software that that can be downloaded free

FREIDEN PRINTER - (1962-1966):

This unit was connected directly to the CDP (Communication Data Processor) and provided a means for inputting and receiving operational commands and messages. It also had a paper tape punch where a paper tape could be punched for use on the High-Speed Paper Tape Reader. The printer used an 8-bit code set since the tape was punched with 8 bits across the tape. The printer appeared to operate at about 100 characters per minute. The printer was placed at one end of the operator's console.

FREQ:

1) File RE-Quest - It is used to get program(s) from a BBS, without logging on line. Only Sysops (system operators) can FREQ files from other Sysops. Users generally ask the Sysop to FREQ file(s) for them.

2) An abbreviation for Frequency.

FREQUENCY:

The number of complete cycles (analog) per unit of time

FREQUENCY BANDS:

The portion of the analog (A.C.) spectrum within a specified upper and lower frequency limit; synonym: frequency range

FREQUENCY DIVISION MULTIPLEXING:

See FDM

FREQUENCY MODULATION:

The frequency of the carrier wave (AC) is changed to correspond to the changes as introduced by input data signal wave.

FREQUENCY RANGE:

Usually a term used to identify the frequencies available within a channel, the lowest to the highest frequency allowed on a channel (line).

FREQUENCY RE-USE:

One example is the frequency re-use in mobile cellular systems: each cell has a frequency that is far enough away from the frequency in the bordering cell that it does not cause interference problems. The same frequency is used at least two cells apart from each other. This practice enables cellular providers to have many times more customers for a given site license.

FREQUENCY SHIFT KEYING:

See FSK

FREQUENCY SPECTRUM:

The continuous range of frequencies beginning with audible sounds in the 20 Hz range to cosmic rays occurring above 1000 gHz (gigahertz). Voice grade telephone channel usable frequency spectrum exists between 300 and 3300 Hz.

FREQUENCY SPECTRUM and BANDS:

Extremely low frequency    (ELF)      30-300 Hz

Voice frequency                   (VF)    300-3000 Hz

Very low frequency            (VLF)        3-30 KHz

Low frequency                     (LF)       30-300 KHz

Medium frequency              (MF)       300-3000 KHz

High frequency                    (HF)         3-30 MHz

Very high frequency           (VHF)        30-300 MHz

Ultra high frequency           (UHF)       300-3000 MHz

Super high frequency         (SHF)          3-30 GHz

Extremely high frequency   (EHF)        30-300 GHz

FRF:

Frame Relay Forum: An association of corporate members consisting of vendors, carriers, users, and consultants committed to the implementation of Frame Relay in accordance with national and international standards.

FRF.11:

Frame Relay Forum implementation agreement for Voice over Frame Relay (v1.0 May 1997). This specification defines multiplexed data, voice, fax, DTMF digit-relay, and CAS/Robbed-bit signaling frame formats but does not include call setup, routing, or administration facilities.

FRF.11 Annex C:

See FRF.12.

FRF.12:

The FRF.12 Implementation Agreement (FRF.11 Annex C) was developed to allow long data frames to be fragmented into smaller pieces and interleaved with real-time frames. This allows real-time voice and non real-time data frames can be carried together on lower speed links without causing excessive delay to the real-time traffic.

FRF.8:

Frame Relay-to-ATM Service Inter-working: To communicate over WAN(s), end-user stations and the network cloud typically must use the same type of transmission protocol. This limitation has prevented differing networks, such as Frame Relay and ATM, from being linked. However, the Frame Relay-to-ATM Service Inter-working (FRF.8) feature allows Frame Relay and ATM networks to exchange data despite differing network protocols.

FRF11-TRUNK:

Point to point permanent voice connection; conforms to the FRF.11

FRMR:

Frame Reject

FRONT-END:

1) Node or software program that requests services of a back end

2) Refer to Communications preprocessor.

FRONT END NETWORK:

A communications network: May interconnect workstations, word processors, personal computers, facsimiles (FAX), terminals, and printers. A front-end network is often a local area network (LAN), and is connected to a front-end processor or a computer's communications port.

FRONT END PROCESSOR:

See FEP

FRTS:

Frame Relay Traffic Shaping: Queuing method that uses queues on a Frame Relay network to limit surges that can cause congestion. Data is buffered and sent into the network in regulated amounts to ensure that the traffic can fit within the promised traffic envelope for a particular connection.

FS, GS, RS, US:

File Separator, Group Separator, Record Separator, and Unit Separator: Information separators used within data in an optional fashion. The hierarchical relationship will usually be FS is the most inclusive, then GS, then RS and US the least inclusive.

FSIP:

Fast Serial Interface Processor: Default serial interface processor for Cisco 7000 series routers. FSIP provides four or eight high-speed serial ports.

FSK:

Frequency Shift Keying (Frequency Modulation ‘FM’):

The carrier (base) frequency is shifted or varied in accordance with the transmitted signal

FSN:  

Forward Sequence Number:  Part of an SS7 MSU that contains the sequence number of the signal unit.

FSSRP:

Fast Simple Server Redundancy Protocol: The LANE simple server redundancy feature creates fault-tolerance using standard LANE protocols and mechanisms. FSSRP differs from LANE SSRP in that all configured LANE servers of an Emulated LAN (ELANE) are always active.

FST:

Fast Sequenced Transport Connectionless: Sequenced transport protocol that runs on top of the IP protocol. SRB traffic is encapsulated inside of IP data-grams and is passed over a FST connection between two network devices, such as routers. FST speeds up data delivery, reduces overhead, and improves the response time of SRB traffic.

FT-1:

Fractional digital service hierarchy level 1: With service in multiples of 56/64Kbps, 2 channels (112/128Kbps) or above, and up to 23 channels. 256/512/768/1024Kbps are common rates for this type of service; also called fractional T1.

FT-3:

Fractional digital service hierarchy level 3: With service in multiples of 1.544Mbps; also called fractional T3.

FTAM:

File Transfer, Access and Management: In OSI, an application layer protocol developed for network file exchange and management between diverse types of computers.

FTP:
File Transfer Protocol: This Internet protocol is used to copy files between computers. FTP can be on the slow side, it doesn't support compression, and it uses cryptic Unix command parameters. FTP features provide for downloading shareware or freeware applications that shield you from the complexities of Unix, and a connection can be made to FTP sites using a Web browser.

FTS:

Federal Telecommunications System

FTS-2000:

The plan through which AT&T and Sprint provide most of the federal government's domestic inter-exchange communications services

FTTC:

Fiber To The Curb: A Network where an optical fiber cable runs from the telephone switch to a curbside distribution point close to the subscriber where it is converted to a copper pair.

FTTH:

Fiber To The Home: A Network where an optical fiber cable runs from the telephone switch to the subscriber's premises.

FTTF:

Fiber to the Feeder

FUBAR:

Fouled Up Beyond All Recognition: Miscue by a person giving a commentary on a project or the world in general; often misspelled FOOBAR.

FUD:

Fear, Uncertainty, and Doubt: A common motivational strategy.

FULL DUPLEX:

See FDX.

FULL MESH:

A term that describes a network in which devices are organized in a mesh topology where each network node has either a physical circuit or a virtual circuit that connects it to every other network node; a full mesh provides a great deal of redundancy but because it is expensive to implement, it usually is reserved for network backbones.

FULL NAME:

A users complete name, usually consisting of the last name, first name, and middle initial. The full name is information that Local Users and Groups or Active Directory Users and Computers can maintain as part of the information identifying and defining a user account.

FULL PERIOD (FP):

A monthly private line service that is rented for the exclusive use of a single customer

FUNCTION CODES:

Usually refers to special codes inserted in paper tape or cards to cause specific machine functions (e.g. tabulate).

FUNCTION SWITCH:

A circuit having a fixed number of inputs and outputs designed so the output information is based on the input information, each expressed in a certain code, signal or pattern. See Boolean algebra

FUNI:

Frame User Network Interface

FURS:

Facilities Utilization Reporting System: A problem and analysis information gathering system.

FUZZBALL:

Digital Equipment Corporation LSI-11 computer system running IP gateway software: The NSF-net used these systems as backbone packet switches.

FX:

Foreign Exchange:

1) A circuit that connects a subscriber in one exchange with a central office (CO) in another exchange.

2) A trunk type that connects a call center with a central office in a remote exchange.

FXO:

Foreign Exchange Office: A FXO interface connects to the Public Switched Telephone Network (PSTN) central office and is the interface to a standard telephone. Cisco's FXO interface is an RJ-11 connector that allows an analog connection at the PSTN central office or to a station interface on a PBX.

FXS:

Foreign Exchange Station: FXS interface connects directly to a standard telephone and supplies ring, voltage, and dial tone. Cisco's FXS interface is an RJ-11 connector that allows connections to basic telephone service equipment, key sets, and PBX(s).