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Below is a list of common computer networking terms and
their definitions.
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LAN – Short for local-area network, a LAN is a
computer network that spans a relatively small area. Most LANs are confined
to a single building or group of buildings. However, one LAN can be connected
to other LANs over any distance via telephone lines and radio waves.
A system of LANs connected in this way is called a wide-area network
(WAN).
WAN – Short for wide-area network,
a WAN is a computer network that spans a relatively large
geographical area. Typically, a WAN consists of two or more
local-area networks (LANs).
Network Hub – A network hub is a
common connection point for devices in a network. Hubs are
commonly used to connect segments of a LAN. A hub contains
multiple ports. When a packet arrives at one port, it is
copied to the other ports so that all segments of the LAN
can see all packets.
Network Switch - In computer networks,
a network switch is a device that filters and forwards packets
between LAN segments. Switches operate at the data link layer
(layer 2) and sometimes the network layer (layer 3) of the
OSI Reference Model and therefore support any packet protocol.
LANs that use switches to join segments are called switched
LANs or, in the case of Ethernet networks, switched Ethernet
LANs.
Network Router - A network router is a
device that forwards data packets along networks. A router
is connected to at least two networks, commonly two LANs
or WANs or a LAN and its ISP’s network. Routers are
located at gateways, the places where two or more networks
connect.
Ethernet - A local-area network (LAN) architecture
developed by Xerox Corporation in cooperation with DEC and
Intel in 1976. Ethernet uses a bus or star topology and supports
data transfer rates of 10 Mbps. The Ethernet specification
served as the basis for the IEEE 802.3 standard, which specifies
the physical and lower software layers. Ethernet uses the
CSMA/CD access method to handle simultaneous demands. It
is one of the most widely implemented LAN standards.
A newer version of Ethernet, called 100Base-T
(or Fast Ethernet), supports data transfer rates of 100 Mbps.
And the newest version, Gigabit Ethernet supports data rates
of 1 gigabit (1,000 megabits) per second.
Firewall – A network firewall is
a system designed to prevent unauthorized access to or from
a private network. Firewalls can be implemented in both hardware
and software, or a combination of both. Firewalls are frequently
used to prevent unauthorized Internet users from accessing
private networks connected to the Internet, especially intranets.
All messages entering or leaving the intranet pass through
the firewall, which examines each message and blocks those
that do not meet the specified security criteria.
There are several types of firewall techniques:
Packet filter: Looks at each packet entering
or leaving the network and accepts or rejects it based on
user-defined rules. Packet filtering is fairly effective
and transparent to users, but it is difficult to configure.
In addition, it is susceptible to IP spoofing.
Application gateway: Applies security mechanisms
to specific applications, such as FTP and Telnet servers.
This is very effective, but can impose a performance degradation.
Circuit-level gateway: Applies security
mechanisms when a TCP or UDP connection is established. Once
the connection has been made, packets can flow between the
hosts without further checking.
Proxy server: Intercepts all messages entering
and leaving the network. The proxy server effectively hides
the true network addresses.
In practice, many firewalls use two or more of these techniques
in concert.
A firewall is considered a first line of
defense in protecting private information. For greater security,
data can be encrypted.
Wi-Fi - Short for wireless fidelity and
is meant to be used generically when referring of any type
of 802.11 network, whether 802.11b, 802.11a, dual-band, etc.
The term is promulgated by the Wi-Fi Alliance.
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