- Fast Ethernet Proposed 100Mbit/s technology for workstation LANs from the eponymous Fast Ethernet Alliance, which includes 3Com and SynOptics. It has been adopted by the IEEE as the basis for the 100BaseT Ethernet standard.
- Fast packet switching A WAN technology capable of transmitting data, digitized voice and digitized image information. It makes use of short, fixed length packets (or cells) that are all the same size. The underlying switching technology is based on the statistical multiplexing of data and voice in fixed length cells. Any of these packets could carry digital voice, data or digital image information. All the packets travel at Level Two of the OSI Model, and routing is performed on the basis of the Level Two addressing. Fast packet is an effective way of making best use of available bandwidth. It offers the benefits of conventional multiplexing techniques and circuit switching techniques. It is one of the transmission technologies being developed for use with B-ISDN. The switch used to route packets in a fast packet network is termed a fast packet switch. Also, fast packet technology can carry data transmissions that enter the network using a frame relay access method. For particularly high speed networking, an implementation of fast packet switching known as ATM is being commercially developed.
- Fault tolerance A method of making a computer system or network resilient to faults or breakdowns to avoid lost data and downtime. For servers this involves such techniques as disk mirroring, disk duplexing or mirrored servers. For LANs and WANs it may involve the use of multiple redundant transmission links.
- Fax server A specialized IVR system which sends facsimile messages to a fax machine designated by DTMF tones. What amounts to a database of fax text resides in the server that is accessed via a user's DTMF phonepad. Requests result in the fax pages being delivered to the chosen fax and the subscriber charged a fee.
- FCC (Federal Communications Commission) US regulatory and approvals agency.
- FCS frame check sequence
- FDDI (Fiber Distributed Data Interface) An optical fiber-based token-passing ring LAN technology with dual counter-rotating rings. Each ring carries data at a rate of 100 Mbit/s using a 125MHz transmission frequency. It has been standardized by the American National Standards Institute (ANSI). An FDDI network has two modes of attachment: a device may be a Single Attach Station - attached to one ring - or a Dual Attach Station - attached to both rings. Typical applications of FDDI are in the area of high speed LAN backbones.
- FIFO first in, first out
- File server A computer, attached to a LAN, that runs a Network Operating System (nos). This lets the file server regulate communications among the workstations connected to it across the LAN, and to manage shared resources available on the file server, such as hard disk storage and printers. A file server may be dedicated: the computer is used only as a file server; or non- dedicated: the underlying computer that the LAN nos runs on is used for another task simultaneously, for example as a workstation.
- Flow control The procedures for controlling the rate of transfer of data between two points in a data network, such as between a protocol converter and a printer. This avoids data loss when a recipient device's buffer is full. Buffers play an essential role in overall flow control in a network.
- FNC (Federal Networking Council) A US group of representatives from those federal agencies involved in the development and use of federal networking, especially those networks using TCP/IP, and the connected Internet. The FNC coordinates research and engineering. Members include representatives from the DoD, DOE, Darpa, NSF, Nasa and HHS.
- Focal point An IBM Network management term; it consolidates the functions needed to manage centrally all parts of a network. It provides an end-to-end network view and receives information from entry points and service points. NetView is IBM's key implementation of the focal point.
- Foirl (Fiber Optic Inter-Repeater Link) Defined in IEEE 802.3 and implemented over two fiber links, transmit and receive, this medium may be up to 500m and 1 kilometer long depending on the number of repeaters in the network.
- Fractional services Bandwidth available from carriers in increments of 64Kbit/s, such as Mercury's Switchband.
- Frame A group of bits sent over a link. A frame may contain control and addressing information, as well as error detection - for example CRC information - and forward error correction information. The size and composition of the frame varies according to the protocol. Often used synonymously with packet.
- Frame relay A data communications interface originating from ISDN designed to provide high speed frame or packet transmission with minimum delay and efficient use of bandwidth. It is a variation on the X.25 interface and form of fast packet switching. It derives its name from using the Data Link or "frame" OSI layer Two to route or "relay" a packet directly to its destination instead of terminating the packet at each switching node. This eliminates processing overheads and increases throughput speed. Based on the ITU-TS Lap-D standard, it uses variable-length packets and applicable only to sub-broadband, T3/E3 or lower, data transmission. Like Ethernet, or token ring, frame relay assumes that connections are reliable. It does not have error detection and error control within the network, which helps to speed up the protocol. When errors occur frame relay relies on higher level protocols for error control. Frame relay is often viewed as a replacement for X.25, primarily for LAN-to-LAN bursty traffic. Voice over frame relay is available, but the subject of debate. It will also become an access method for ATM-based WANs.
- FDM (Frequency Division Multiplexing) A multiplexing scheme in which the available transmission frequency range is divided into narrower bands. Each of these bands is used to carry a separate channel.
- FSK (Frequency Shift Keying) A technique for modulating data that use two frequencies. Frequency shifts between the two frequencies are generated when the binary digital level changes. So one particular frequency is used to represent a binary one, and a second frequency is used to indicate a binary zero. FSK is used in low speed modems when, in full-duplex transmission, two different frequencies are used in each direction, resulting in four different frequencies being used.
- Front end The client part of a client/server application that requests services across a network from a server, or back end. It typically provides an interactive interface to the user, for example, a data entry front end, allowing data to be entered into a server through the use of SQL.
- FTAM (File Transfer Access and Management) ISO 8671 standard which plays a key role in integrated message handling as the vehicle for interchanges of EDI information between applications. FTAM controls the transfer of whole files or parts of files between end systems.
- FTP (File Transfer Protocol) The TCP/IP standard, high-level protocol for transferring files from one machine to another. Usually implemented as applications level programs, FTP uses the Telnet and TCP protocols. Full duplex - A channel capable of transmitting in both directions at the same time.
- Functional profile A defined stack of ISO OSI Layer elements, such as Gosip, Map or Top. Functional profiles were developed in order to ensure that, when defined, ISO OSI stacks could interoperate. Due to the different protocol elements at each OSI layer, it was possible to define stacks that were syntactically correct, but would not be able to exchange in-formation due to differences at particular layers. A functional profile that has been defined as a standard is a standardized profile. Likewise, an International Standard Profile is an OSI functional profile.