F

Fault Tolerance
The ability of a network or component to keep working, despite the malfunction or failure of some of its devices is referred to as fault tolerance. For example, redundant components and communication links are essential features of fault tolerant systems.

Failover
Failover is the process of automatically switching from a failed primary device or link to a backup device or link, preferably so fast that users or other devices are not aware of the failure.

Fiber Optic Interrepeater Link (FOIRL)
FOIRL is an early specification for running 10-Mbps Ethernet over fiber optic cable. The IEEE 10BaseF specification is intended to replace FOIRL.

Fibre Channel
Fibre Channel is a very high-speed, fiber optic data transfer interface based on ANSI FCS. FCS can carry multiple existing protocols, including IP and SCSI.

File Transfer Protocol (FTP)
FTP is a TCP/IP Application Layer protocol used to transfer information between a client and server attached to a network.

Firewall
A firewall is a controlled access point between sections of the same network, designed to confine problems to one section. A firewall is also a controlled access between a private network and public network (such as the Internet), and is often implemented with a router and special firewall software. See proxy server and dual-homed gateway.

Frame
A frame is a unit of information transmitted across a data link. There are two types of frames, a control frame and an information frame. Control frames are used for initial setup and to manage the link. Information frames contain information from layers above the Data Link Layer.

Frame Relay
A frame relay is essentially an electronic switch. Physically, it is a box that connects to three or more high-speed links, and routes data traffic between them. Frame relay is intended only for data communications, not voice or video. Transmission errors are detected but not corrected (the frame is discarded).

Front End Processor (FEP)
A FEP is a device used in IBM mainframe networks that provides connectivity between networking devices and a mainframe. A FEP is also referred to as a communications controller.

Flow Control
Flow control is a method of controlling the amount of frames or messages that are sent between two computer systems. Practically every data communications protocol contains some form of flow control to keep the sending computer from sending too many frames or packets to the receiving node.

Fiber Distributed Data Interface (FDDI)
FDDI protocol is used in local area networks (LANs) for connecting devices and/or workgroups at 100 megabits per second (Mbps) over fiber optic cable. FDDI is often used as a backbone for LANs.

File Transfer Protocol (FTP)
FTP is an application layer protocol used in Transmission Control Protocol/Internet Protocol (TCP/IP) networks. FTP is a program that can be used to transfer files between hosts on the Internet.

Final Design
Final Design is another name given to the Physical Design phase.

Firewall
According to the National Computer Security Association, a firewall is "a system or combination of systems that enforces a boundary between two or more networks." It is a controlled gateway between one network and another, typically between a private network and the Internet.

Flooding
Flooding is when the same signal is transmitted out all ports of a bridge, switch, or router.

Frame Latency
Frame latency is the transmission delay created as a device processes a frame. It is the duration from the time a device reads the first byte of a frame, until the time it forwards that byte.

Fractional T1
Fractional T1 is a telephone company service that provides data rates from 64 Kbps to 1.544 Mbps, by allowing a user to purchase one or more channels of a T1 link. If a customer needs less bandwidth than 1.544 Mbps, fractional T1 is a low-cost alternative to purchasing a full T1.