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.
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.
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.
