Mechanism used by ATM networks when rigorous path selection 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.

Flexible Access Network

A technology offering variable bandwidth, rapid service provisioning, service variety and customer control. FAN on second reference.

Panel of I/O connectors that attaches to an equipment rack, providing easy access for data connections to a networking.

Frequently Asked Question

Federation of American Research NETworks

A LAN transmission standard with a data rate of 100 Mbps. A workstation with a 10 Mbps (10Base-T) Ethernet card can be connected to a Fast Ethernet network.

Federal Communications Commission

A regulatory authority for telecommunication in the US.

Frame Check Sequence

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

Frequency Division Duplex

Provides for simultaneous transmission and reception of radio signal. This allows the mobile phone user to talk and listen at the time. The mode of communication is facilitated by having a frequency channel with two separate operating frequencies, one for transmission and the other for reception.

Fibre Distributed Data Interface

The ANSI  standard for 100 Mbps local area networks.

Fibre Distributed Data Interface II

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

Frequency Division Multiplexing

Method by which the available transmission frequency range is divided into narrower bands; each of these bands is used for a separate channel. This allows several signals to be sent over the same transmission medium.

Forward Error Correction

An error correction technique in which redundant bits are transmitted along with the payload enabling the receiving station to detect error and to correct the message.

Forward Explicit Congestion Notification

Bit set by a Frame Relay network to inform DTE receiving the frame that congestion was experienced in the path from source to destination. DTE receiving frames with the FECN bit set can request that higher-level protocols take flow-control action as appropriate.

Front-End Processor

Device or board that provides network interface capabilities for a networked device.

Flexible access network Four Dragons

South Korea, Hong Kong, Singapore, Taiwan.

Frequency-Hopping Spread-Spectrum

A spread-spectrum techniques that operate over the radio airwaves in the unlicensed ISM band (industrial, scientific, and medical). FHSS uses a technique by which the signal transmitted hops among several frequencies at a specific rate and sequence as a way of avoiding interference. WECA’s focus is on the use of DSSS for 11 Mbps high rate wireless LAN communications. (See also FH-CDMA)

Category of popular network applications that allow files to be moved from one network device to another.

Generally, a process or 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.

A hardware/software tool that allows a network administrator to determine what type of users can access the resources on the network. The firewall provides a mechanism to monitor and funnel data from authorized users (only) through the firewall to and from the network. A firewall may be a software program that runs on UNIX or other platforms, or it may be a part of a proprietary operating system. A firewall by itself does not perform the routing function.

Fibre-optic Link Around the Globe

A proposal by a consortium led by Nynex Corp. to extend a 25,000-kilometer cable from the United Kingdom to eastern Asia via the Middle East.

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

SS7 fully associated link. An SS7 signalling link directly associated with a link carrying traffic.

Flip Chip Ball Grid Array

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

Stream of data travelling between two endpoints across a network (for example, from one LAN station to another). Multiple flows can be transmitted on a single circuit.

Technique for 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 the transmission until the data in the buffers has been processed. In IBM networks, this technique is called pacing.

Fallback/fall-forward Line Sensing

A feature that enables a high-speed analogue modem to monitor the quality of the phone line and to step down to the next lower speed if the line quality deteriorates. The modem falls forward to the next higher speed as line quality improves.

Full Line Terminal

Multiplexer that terminates a SONET span.

Frequency Modulation

Modulation technique in which signals of different frequencies represent different data values.

Federal Networking Council

Group responsible for assessing and coordinating U.S. federal agency networking policies and needs.

Fibre-Optic Interrepeater Link

Fibre-optic signalling methodology based on the IEEE 802.3 fibre-optic specification. FOIRL is a precursor of the 10BaseFL specification, which is designed to replace it.

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

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

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

Fibre Optics Transmission Systems

Vendor-proprietary fibre-optic transmission equipment.

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

Field Programmable Gate Array

Fully Qualified Domain Name

FQDN is the full name of a system, rather than just its host name. For example, aldebaran is a host name, and aldebaran.interop.com is an FQDN.

Frame Relay

Frame Relay Access Device

Any network device that provides a connection between a LAN and a Frame Relay WAN.

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

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

A segment of a digital signal that has a repetitive characteristic in that corresponding elements of successive frames represent the same things. In a time-division multiplex system, a frame is a sequence of time slots, each containing a sample from one of the channels served by the multiplex system; the frame is repeated at the sampling rate, and each channel occupies the same sequence position in successive frames.

The emerging standard for high-speed data communications, offering users transmission speeds of 2.048 megabits per second and higher. It allows faster speeds than the X.25 packet switching standard because it does away with elaborate error-correction and routing information. Its main application is interconnecting local area networks. (2) Connection-oriented, fast packet technology for either public or private local or wide area networks; implemented as a permanent virtual circuit. More efficient than X.25.

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

A synchronous protocol that encapsulates data into frames.

Frame Relay Access Service Module

The European term for toll-free 800 services.

Number of cycles per unit of time, measured in units called Hertz (Hz). One Hz equals one cycle per second.

A transmission technology in which packets of information hop along the clearest frequencies in a bandwidth.

File Transfer Access and Management

The standard for the transfer of whole files or parts of files between end systems.

File Transfer Protocol

A feature of the Internet that allows users to transfer files from other hosts.

A server that a user can contact in order to transfer files by means of the File Transfer Protocol (FTP) over a TCP/IP network.

File Transfer Protocol Filter

Capability for simultaneous data transmission between a sending station and a receiving station.

In frame relay, a link-management message function that provides the user device with the complete status of all permanent virtual circuits (PVCs) configured on the link.

Frame User Network Interface

Foreign Exchange Office

An FXO interface connects to the Public Switched Telephone Network's (PSTN) central office and is the interface offered on a standard telephone. Cisco's FXO interface is an RJ-11 connector that allows an analogue connection to be directed at the PSTN's central office or to a station interface on a PBX.

Foreign Exchange Station

An 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, keysets, and PBXs.