A LAN is a network confined within a limited geographic area that connects computers. LANs can connect as few as three computers but often link hundreds used by thousands of people. Standard networking protocols and media have resulted in widespread use of LANs in businesses and schools. Common LAN technologies include Ethernet, phone lines, and wireless. Ethernet uses coaxial or twisted pair cabling and a hub to connect computers, while phone lines use existing telephone wiring. Wireless networks use radio signals and no cabling.

3. A network is any collection of independent computers that
communicate with one another over a shared network
medium. LANs are networks usually confined to a
geographic area, such as a single building or a college
campus. LANs can be small, linking as few as three
computers, but often link hundreds of computers used by
thousands of people. The development of standard
networking protocols and media has resulted in worldwide
proliferation of LANs throughout business and educational
organizations.

5. You must also choose a type of networking
technology, sometimes referred to as the LAN
media, which enables your computers to send
information to each other. The most common
networking technologies used for home
networking include:
 Ethernet
 Phone line
 Wireless

6. Used in organization networks, Ethernet is widely known,
supported, and understood. Ethernet equipment consists of
an Ethernet adapter and either coaxial cable (for 10Base2)
to serially connect each computer together, or twisted pair
cable (for 10BaseT or 100BaseT) to connect each computer
to a hub. A hub is required when you are using twisted pair
cabling and connecting more than two 10BaseT or
100BaseT computers together.
While Ethernet adapters are generally low cost, the cabling
and hub needs add to the complexity and cost.
Ethernet can operate at speeds of 10 megabits per second
(Mbps) or 100 Mbps. To get 100 Mbps, you must use 100
Mbps Ethernet adapters, Category 5 twisted pair cabling,
and connect to 100 Mbps port on an Ethernet hub.

8. Used mostly in home and small office networks,
phone line uses telephone wiring as its medium
for communication and operates at speeds up
to 10 Mbps. Phone line equipment consists of a
phone line adapter installed in each computer
and standard telephone cables connected to
standard phone jacks.
The advantage of phone line networks is phone
jacks are usually found throughout the house
and close to areas where computers are used.

10. Used in both organization and home networks,
wireless technology uses radio signals to
communicate so there is no cabling required. Wireless
solutions are gaining popularity and becoming more
affordable. There are many wireless products,
however, wireless networks based on the IEEE 802.11
standard are becoming the preferred solution.
Organization or large business wireless networks are
more likely to be using IEEE 802.11. If your home or
small network is also based on IEEE 802.11, you can
use the same network adapter to access both work
and home or small office networks. IEEE 802.11b can
operate at a speed of 11 Mbps. Wireless equipment
consists of a wireless adapter installed in each
computer.

13. Coaxial cable, or coax, is an Electrical cable with an inner
conductor surrounded by a flexible, tubular insulating
layer, surrounded by a tubular conducting shield.
Coaxial cable is used as a transmission line for radio
frequency signals, in applications such as feed lines
connecting radio transmitters and receivers with their
antennas, computer network (Internet) connections, and
distributing cable television signals. One advantage of
coax over other types of radio transmission line is that in
an ideal coaxial cable the electromagnetic field carrying
the signal exists only in the space between the inner and
outer conductors. This allows coaxial cable runs to be
installed next to metal objects such as gutters without the
power losses that occur in other types of transmission
lines, and provides protection of the signal from external
electromagnetic interference.

14. A: OUTER PLASTIC SHEATH
B: WOVEN COPPER SHIELD
C: INNER DIELECTRIC INSULATOR
D: COPPER CORE

15. A firewall is a device or set of devices designed to
permit or deny network transmissions based
upon a set of rules and is frequently used to
protect networks from unauthorized access while
permitting legitimate communications to pass.
Many personal computer operating systems
include software-based firewalls to protect
against threats from the public Internet. Many
routers that pass data between networks contain
firewall components and, conversely, many
firewalls can perform basic routing functions.

17. A router is a device that forwards data packets
between telecommunications networks, creating an
overlay internetwork. A router is connected to two or
more data lines from different networks. When data
comes in on one of the lines, the router reads the
address information in the packet to determine its
ultimate destination. Then, using information in its
routing table or routing policy, it directs the packet to
the next network on its journey or drops the packet. A
data packet is typically forwarded from one router to
another through networks that constitute the
internetwork until it gets to its destination node.[1]

19. A network switch or switching hub is a computer
networking device that connects network
segments.
The term commonly refers to a multi-port network
bridge that processes and routes data at the data
link layer (layer 2) of the OSI model. Switches that
additionally process data at the network layer
(Layer 3) and above are often referred to as Layer
3 switches or multilayer switches.

21. An Ethernet hub, active hub, network hub, repeater
hub or hub is a device for connecting multiple twisted
pair or fiber optic Ethernet devices together and
making them act as a single network segment. Hubs
work at the physical layer (layer 1) of the OSI model.
The device is a form of multiport repeater. Repeater
hubs also participate in collision detection, forwarding
a jam signal to all ports if it detects a collision.
Hubs also often come with a BNC and/or Attachment
Unit Interface (AUI) connector to allow connection to
legacy 10BASE2 or 10BASE5 network segments. The
availability of low-priced network switches has largely
rendered hubs obsolete but they are still seen in older
installations and more specialized applications.

23. Category 5 cable (Cat 5) is a twisted pair cable for
carrying signals. This type of cable is used in
structured cabling for computer networks such as
Ethernet. It is also used to carry other signals
such as telephony and video. The cable is
commonly connected using punch down blocks
and modular connectors. Most Category 5 cables
are unshielded, relying on the twisted pair design
and differential signaling for noise rejection.
Category 5 has been superseded by the Category
5e specification.

25.  Use a switched network: A switch can separate a network into
many parts which can effectively preventing snooping and
sniffing on a network. These switches also reduce network
traffic by limiting messages to only the parts of the network on
which they are needed to improve the efficiency of the whole
network.
 Bridges and Routers: Bridges and routers are electronic filters
which only pass a network message through themselves if the
destination lies on the other side of the filter. Consequently if
"the snooper" is on one side of a bridge or router they will not
see any traffic passing between computers on the other side of
the filter.
 Lan Security Architecture (LSA): a proprietary technique where
twisted pair hubs inspect incoming messages and will only
transmit them unscrambled to the destination computer. All
other computers on the hub receive scrambled messages.

26.  Encryption: Encrypting the data passing between
your computer and its destination. There are many
encryption technologies and product available
which effective protect information and data privacy.
The popular encryption methods used are PGP
(Pretty Good Privacy).
 verification: Use user name and password to verify
users. It is necessary to encrypt the password and
implement timestamps making forgery extremely
difficult.
 Combination technologies: Many new technologies
are available which doing both verification and
encryption. One of such technologies is Kerberos
which uses tokens, timestamps, tickets and
encryption to make transactions between
computers secure.