Transcript Transfer of data in ICT systems

Networks
Networks
What is a computer network?
A network is two or
more computers that
are linked together
so that they are able
to share resources.
Networks
Shared resources include
• Hardware – printers, scanners,
storage, etc.
• Software – need only be
installed on one computer.
• Data (e.g. database files).
• An Internet connection.
Networks
Advantages & Disadvantages
Advantages
Disadvantages
•Data can be shared making
it easier to work together.
•Computers can share
hardware like printers – no
need to buy more than one,
so it is cheaper.
•It is quicker to update
software – it is stored in
one place on a server.
•Viruses can be easily
spread through networks.
•If data and software is all in
one place, all computers will
not work if the network
experiences problems.
•Networks require regular
maintenance – this is
expensive.
Networks
Internet, Intranet, Extranet
Service/
Hardware
Explanation
Internet
The Internet is a WAN which is made up of many other smaller
networks.
An extranet is an external network which can be viewed by many
different people at an organisation such as employees, customers,
suppliers and shareholders.
This internal network is private to one organisation, viewable to
employees only.
Extranet
Intranet
Networks
LANs and WANs
Local area networks:
• Confined to a small area.
• Usually located in a single
building.
• Use cable, wireless, infrared
and microwave links that are
usually owned by the
organization.
• Cheap to build.
• Cheap to run.
Wide area networks:
• Cover a wide geographical
area (i.e., between cities,
countries and even
continents).
• In lots of different buildings
and cities, countries, etc.
• Use more expensive
telecommunication links that
are supplied by telecom
companies.
• Expensive to build.
• Expensive to run.
Networks
Network Topologies
• Ring
• Bus
• Star
Networks
An ICT network consists of
• Hardware/communication devices
• Network software
• Data transfer media
Networks
Communication devices
A network interface card:
• prepares data for
sending over the
network
• sends the data
• controls the flow of
data.
Networks
Communication devices
A hub:
• is used to join
computers in a network
• allows the connection
of cables
• allows the sharing of
files and Internet
access
Networks
Communication devices
A switch:
• is similar to a hub but more intelligent
• can look at a packet of data to decide
where it should go
• reduces the number of packets of
data on a network, which speeds it up
Networks
Communication devices
A router:
• can be wired or
wireless
• is used to join several
networks together
• is often used to
connect several
computers in the home
to the Internet
Networks
Gateways, Bridges, Packet
Switches
Service/
Hardware
Explanation
Gateways
These allow two different networks to speak to one
another by translating data.
These are used to join – or bridge – two LANs together to
form one larger network.
Switches can speed up networks by only sending packets
of data to the computers which need the data. This means
that less data is travelling unnecessarily around the entire
network.
Bridges
Packet
switching
Networks
Network software
Network software consists of:
• Network operating systems – specialist
operating systems designed specifically for
networks.
• Network management software – used to help a
network manager run a network by keeping
track of software, keeping software up-to-date,
installing software security patches, helping to
manage the help-desk, etc.
Networks
Data transfer media
The medium/method
by which the data is
transferred in a
network can be:
• metal wire
• fibre optic cable
• wireless.