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F
Fast Ethernet
Fast Ethernet
is Ethernet that runs at 100Mbps as opposed to the standard 10Mbps. There
are two primary standards that have been proposed: 100Base-T and
100VG-AnyLAN. 100Base-T is also referred to as the IEEE 802.3u standard.
The 100VG-AnyLAN standard is in the hands of a new committee, the IEEE
802.12. Fast Ethernet and the 100Base-T standard are synonymous terms.
Fast Packet Switching
Fast
packet switching is a new packet switching technology that operates at the
physical layer and lower Data Link sublayer of the OSI protocol stack.
Because it is located at these low layers (only a small amount of
processing is needed) and because of small packet sizes, it operates at
very high speeds. Performance is also increased because the end nodes (and
not the network) handle error checking and recovery.
Fast Select
Fast
Select is an X.25 protocol option that allows the user to send a small
amount of information while simultaneously establishing and breaking the connection.
Only one packet is needed to do all three functions.
FCC
FCC stands for
Federal Communications Commission. It has the authority to regulate all
interstate telecommunications traffic in the United States.
FDM
FDM stands for
frequency division multiplexing. Frequency division multiplexing was
developed to allow several voice signals to be transmitted (multiplexed)
simultaneously over a single trunk.
FEC
Forward error
correction, or FEC, is the method used by a receiving station or modem that
allows for the correction of transmission errors without the need to
re-send the data.
FEP
FEP stands for
front end processor. An FEP is used by a mainframe to handle the details of
the network when sending and receiving data from the network. This keeps
the host processor from having to handle the processing associated with
routing data through the network.
Fibre Channel
The
American National Standards Institute (ANSI) created the fibre channel
standard in 1988. The X3T9.3 committee developed this standard to fill the
need for a very high-speed data transfer among workstations, mainframes,
super computers, storage, and display devices.
File Transfer
Two
data manipulation capabilities are universally required by network users:
the ability simply to copy a file from one node to another, called file
transfer, and the ability to share a file that resides on another node,
called file sharing or remote file access.
File
transfer is straightforward: the user issues commands specifying the source
and destination, and the file transfer facility transfers the file, leaving
the original intact and creating a copy on the target node. Of course, the
data might need to be transformed if the source and destination nodes are
different. In the context of the OSI model, lower levels handle this. In
the case of other environments, such as TCP/IP, the application itself must
take care of it. Examples of file transfer protocols are FTP (File Transfer
Protocol), XModem and ZModem.
FINGER
FINGER is an
Internet utility that provides information about the users who are
connected to an Internet server. It is an early version of the current
Domain Name Service (DNS) which is widely used today.
Flag
In the context of
networking and data communications, a flag has several meanings. In the
Novell world it is a command which will give a file's attributes. In the
IBM SDLC world it is a frame delimiter. In the TCP/IP world, flags control
fragmentation.
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.
Fractional T1
Fractional
T1 (FT1) is a service offered by the phone company which provides users of
telecommunications services optional data rates from 64Kbps to 1.544Mbps.
It is called Fractional T1 because the user can specify the desired rate
that is a fraction of the normal T1 rate (1.544Mbps). It is a low cost
alternative to purchasing a full T1 and only using a portion of the
bandwidth.
Fragmentation
The term
fragmentation is usually used in the context of the Transmission Control Protocol/Internet
Protocol (TCP/IP). It is the process that is used by the IP layer to divide
large messages into smaller pieces before sending them to the Data Link
Layer for transmission. It is necessary to do this because a protocol such
as Ethernet has a maximum frame size of 1500 bytes. If the IP packet is
larger than 1500 bytes then fragmentation is used for the transfer.
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. Examples of control frames (from
the LAP-B protocol) are receiver ready (RR) and receiver not ready (RNR)
which tell the sender whether or not the receiver is capable of accepting
frames. Information frames contain information from the layer above, the
Network 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. Only connection-oriented service is provided. Transmission errors
are detected but not corrected (the frame is discarded).
Frequency Bands
There
are several ranges of frequencies that are generally accepted. These are
listed below:
- ELF-Extremely Low Frequency: Below 300Hz
- ILF-Infra Low Frequency: 300Hz to 3KHz
- VLF-Very Low Frequency: 3KHz to 30KHz
- LF-Low Frequency: 30KHz to 300KHz
- MF-Medium Frequency: 300KHz to 3MHz
- HF-High Frequency: 3MHz to 30MHz
- VHF-Very High Frequency: 30MHz to 300MHz
- UHF-Ultra High Frequency: 300MHz to 3GHz
- SHF-Super High Frequency: 3GHz to 30GHz
- EHF-Extremely High Frequency: 30GHz to
300GHz
- THF-Tremendously High Frequency: 300GHz to
3THz
Frequency Modulation
Frequency
modulation is a method of modifying a signal so that it can carry
information. The carrier (original sine wave) has its frequency modified to
correspond to the information being carried.
FTP
FTP stands for
File Transfer Protocol. FTP is an application layer protocol used in TCP/IP
networks. FTP is a program that can be used to transfer files between hosts
on the Internet. There are two ways to use FTP, regular FTP and anonymous
FTP. To use regular FTP you must have an account with the remote host.
Anonymous FTP does not require an account and allows access to thousands of
archives such as public domain software.
Full Duplex
Full-duplex
means that data are transmitted in both directions at the same time, using one
wire-pair for each direction. In principle, full duplex allows data to flow
in both directions simultaneously.
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