FAS
Frame Alignment Sequence - Telephony

FAST Ethernet
100BASE-T, IEEE 802.3u 
Ethernet specification for 100 Mb/s transmissions over unshielded twisted pair or fiber optic cable. 

Fault Tolerance
The ability of a program or system to operate properly even when a fault occurs. Fault-tolerant systems are designed to ensure that even in the event of a power failure, a disk crash, or a major user error, for example, data is not lost and the system can continue operation. 

FC
Fiber-Optic Connector

FC
Frame Control.
The third byte in a token ring frame. Contains info. from the LLC or MAC sub-layers. 

FC-IP
Fiber Channel over IP

FCS
Frame Check Sequence

FDDI
Fiber Distributed Data Interface - ANSI defined standard. 100 Mbps
A specification developed by ANSI and IEEE for high-performance fiber optic networks operating on two counter-rotating rings at 100 Mb/s. 

FDM
Frequency Division Multiplexing 
A technique whereby information from multiple channels can be allocated bandwidth on a single wire based on frequency.

FDMA
Frequency Division Multiplexing Access

FEC
Forwarding Equivalence Class - MPLS 
In data transmission, a process by which data is added that is derived from the payload by an assigned algorithm. It allows the receiver to determine if certain classes of errors have occurred in transmission and, in some cases, allows other classes of errors to be corrected.

FECN
Forward Explicit Congestion Notification 
A bit set by a frame relay network to notify an interface device - DTE - that congestion avoidance procedures should be by the receiving device.

FEP
Front End Processor 
ex. IBM ¨ 3745 - A special purpose communications processor designed to off-load the mainframe of communications functions such as message handling, code conversion, and error control.

FHSS
Frequency Hopping Spread Spectrum
Radio wave modulation for wireless network. Older and less reliable than DSSS.

Firewall
Network Security Component. A software component that acts as a filter restricting specific types of network packets from passing from one network to another.

FIREWIRE
IEEE 1394

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

FLP Burst
Fast Link Pulse Burst 
A burst of 100BASE-T link test pulses that encapsulate auto-negotiation information for identifying the speed and mode at which a device operates. 

FLT
Full Line Terminal - Sonet

FMD
Function Management Data 

FOIRL
Fiber Optic Inter Repeater Link 
Fiber-optic signaling methodology based on the IEEE 802.3 fiber-optic specification.

FOMAU
Fiber Optic Medium Attachment Unit. 
An IEEE 802.3 MAU that uses a fiber optic medium. 

FOTS
Fiber-Optic Transmission System

FPGA
Field Programmable Gate Array

FPLMTS
Future Public Land Mobile Telecommunications Systems. 
The original term for IMT-2000

FPS
Fast Packet Switching

FPU
Frame Processing Unit. 
A device used to recognize and analyze various network frames in order to gather network statistics. 

FRAD
Frame Relay Assembler Dissembler. 
Providing connectivity to a frame relay network for non-frame relay devices.

FRAME

FRAME RELAY
A high-speed packet switching protocol popular in networks, including WAN's, LANs, and LAN-to-LAN connections across vast distances. 


FRF.11
Frame Relay Forum - 
Voice Over Frame Relay. Specifies a process to connect a PBX on a Frame Relay network for voice, data and fax. FRF.12 A procedure which divides large 

FRMR
Frame Reject

FRU
Field Replaceable Unit

FSI
FDDI System Interface

FSMA
Field-Installable Subminiature Assembly. 
A type of threaded connector for fiber optic cable called out in the 802.3 FOIRL specification. 

FSPF
Fiber Shortest Path First - Brocade ¨ 
Based on OSPF used for Fiber Channel.

FST/IP
Fast-Sequenced Transport 
Encapsulation for source-route bridging on IP networks.

FTAM
File Transfer Access and Management. 
An OSI application.

FULL DUPLEX
A capability for simultaneous transmission of data in both directions 

FXO
Foreign Exchange Office 
The FXO interface is an RJ-11 connector that allows a connection to be directed at the PSTN's central office (or to a standard PBX interface, if the local telecommunications authority permits). This interface is of value for off-premise extension applications.

FXS
Foreign Exchange Station 
The Foreign Exchange Station " interface. This interface is an RJ-11 connector that allows connection for basic telephone equipment, key sets PBXs, and supplies ring, voltage, and dial tone.