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.
Users can protect their work on a network by having
a strong password, and changing it frequently.
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
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
An ICT network consists of
• Hardware/communication devices
• Network software
• Data transfer media
Networks
Network Topologies
Bus
• PCs connected to the next in a row with a central backbone
• If a PC or link fails or breaks the whole system fails
The more PCs the poorer the performance
Difficult to locate faults
Easy to add additional PCs
Networks
Ring
 Fast
 Better, faster performance than a bus topology
BUT
 If one cable breaks then all computers will not
work, as data only travels in one direction.

Networks
• All PCs and peripheral devices
connected to switch/router/hub.
Star Network
 If one cable breaks or one device fails the rest
continue to work
 Easy to maintain and add PCs, no loss in
performance
• Large amount of cabling needed
• Expensive to buy needed hardware (hubs and
switches etc)
Networks
Company-School-Hospital
Intranet Robert-Hole
Gurney-Dixon
An Intranet is a private
network, usually several
buildings linked together with fibreoptic cable to the main server
building. Think of Learners Pool.
Tech
Main Block
Firewall
Nichols
IPS servers
Internet
Networks
Company-School-Hospital Extranet
This is when employees or users of a private
Intranet can gain access to this network away
from their place of work, or school.
An example is you using Ranger Outpost to gain
access to the private Priestlands School Intranet.
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
• It can look at a packet of data to decide where it
should go. For example;
• A hub network has 7 computers and 1 printer
attached. When 1 computer sends a message to the
printer to print, the request goes to everything on
that hub, trying to find the printer. This can cause a
collision of data, slowing the network down.
• A switch allows the computer wanting to print to go
straight to the printer and not waste time trying to
find it. Hubs are therefore being replaced by
switches.
Networks
Communication devices
A router:
• IS VERY POWERFUL and
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
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.
Networks
Gateways
• Joins together two
networks that use
different base
protocols
• Links different
types of networks
• Links LAN to WAN
• Allows a LAN to
connect to the
internet
Networks
Bridge
• Joins together two networks that use the
same bas e protocols.
• Links similar types of networks.
• Links LAN to LAN.
Networks
Tasks:
1. What is a network?
2. Why do we have them?
3. What can they share?
4. What 3 types of topologies are there? Explain the differences
and advantages of each.
5. What is a LAN? Give an example.
6. What is a WAN? Give an example.
7. What is an INTRANET? Give an example.
8. What is an EXTRANET? Give an example.
9. What is a hub?
10.What is a router?
11.What is a switch, and what does it do?
12.What is a Bridge?
13.What is a Gateway?
14.Give 2 ways of protecting data on a network.