Filter
Top Products
Firewall - A firewall is a set of related programs, located at a network gate-
way server, that protects the resources of a network from users from other
networks. (The term also implies the security policy that is used with the pro-
grams.) An enterprise with an intranet that allows its workers access to the
wider Internet installs a firewall to prevent outsiders from accessing its own
private data resources and for controlling what outside resources to which its
own users have access.
Basically, a firewall, working closely with a router, examines each network
packet to determine whether to forward it toward its destination.
Firmware - Code that is written onto read-only memory (ROM) or program-
mable read-only memory (PROM). Once firmware has been written onto the
ROM or PROM, it is retained even when the device is turned off.
Fragmentation - Breaking a packet into smaller units when transmitting over
a network medium that cannot support the original size of the packet.
FTP (File Transfer Protocol) - A protocol used to transfer files over a TCP/IP
network (Internet, UNIX, etc.). For example, after developing the HTML
pages for a Web site on a local machine, they are typically uploaded to the
Web server using FTP.
FTP includes functions to log onto the network, list directories and copy files.
It can also convert between the ASCII and EBCDIC character codes. FTP
operations can be performed by typing commands at a command prompt or
via an FTP utility running under a graphical interface such as Windows. FTP
transfers can also be initiated from within a Web browser by entering the
URL preceded with ftp://.
Unlike e-mail programs in which graphics and program files have to be
"attached," FTP is designed to handle binary files directly and does not add
the overhead of encoding and decoding the data.
Full Duplex - The ability of a device or line to transmit data simultaneously
in both directions.
Gateway - A device that interconnects networks with different, incompatible
communications protocols.
119
Layer 2 Management 4-Port Gigabit Ethernet Switch
ProConnect II
®
Series
118
Dynamic Routing - The ability for a router to forward data via a different
route based on the current conditions of the communications circuits. For
example, it can adjust for overloaded traffic or failing lines and is much more
flexible than static routing, which uses a fixed forwarding path.
Encryption - A security method that applies a specific algorithm to data in
order to alter the data's appearance and prevent other devices from reading
the information.
ESS (Extended Service Set) - A set of more than two or more BSSs (multiple
access points) forming a single network.
Ethernet - IEEE standard network protocol that specifies how data is placed
on and retrieved from a common transmission medium. Has a transfer rate of
10 Mbps. Forms the underlying transport vehicle used by several upper-level
protocols, including TCP/IP and XNS.
Fast Ethernet - A 100 Mbps technology based on the 10Base-T Ethernet
CSMA/CD network access method.
FHSS (Frequency Hopping Spread Spectrum) - FHSS continuously changes
(hops) the carrier frequency of a conventional carrier several times per second
according to a pseudo-random set of channels. Because a fixed frequency is
not used, and only the transmitter and receiver know the hop patterns, inter-
ception of FHSS is extremely difficult.
Fiber Optic - The medium and the technology associated with the transmis-
sion of information as light impulses along a glass or plastic wire or fiber.
Fiber optic wire carries much more information over longer distances than
conventional copper wire and is far less subject to electromagnetic interfer-
ence.
Fiber Optic Cable - A transmission medium that uses glass or plastic fibers
rather than copper wire to transport data or voice signals. The signal is
imposed on the fibers via pulses (modulation) of light from a laser or a light-
emitting diode (LED). Because of its high bandwidth and lack of susceptibili-
ty to interference, fiber optic cable is used in long-haul or noisy applications.
Finger - A UNIX command widely used on the Internet to find out informa-
tion about a particular user, such as telephone number, whether currently
logged on or the last time logged on. The person being "fingered" must have
placed his or her profile on the system. Fingering requires entering the full
user@domain address.