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					GCSE Revision
                           NETWORK TOPOLOGIES

A computer network is a collection of computers connected together

Local area networks (LAN's)

A local area network 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.

Most LANs connect workstations and personal computers. Each node
(individual computer) in a LAN has its own CPU with which it executes
programs, but it is also able to access data and devices anywhere on the
LAN. This means that many users can share expensive devices, such as
laser printers, as well as data. Users can also use the LAN to communicate
with each other, by sending e-mail or engaging in chat sessions.

Network topologies

Topologies are the shape of a local area network (LAN) or other
communication systems. There are three principal topologies used in LANs.

Ring: All devices are connected to one another in the shape of a closed loop,
so that each device is connected directly to two other devices, one on either
side of it. Ring topologies are relatively expensive and difficult to install, but
they offer high bandwidth and can span large distances.
Bus : All devices are connected to a central cable, called the bus or
backbone. Bus networks are relatively inexpensive and easy to install for
small networks. Ethernet systems use a bus topology.

Star: All devices are connected to a central hub. Star networks are relatively
easy to install and manage, but bottlenecks can occur because all data must
pass through the hub.

Wide area networks (WAN's)

A wide area network is a computer network connecting a number of Local
Area Networks (LAN's)

Sample GCSE question

What are the key differences between a LAN and WAN network?

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