Higher Grade Computing Studies
5. Networks
Categories of Computer - Network Computer
• Computers are networked for the
purpose of sharing hardware,
software and data.
• Alternatively, the main reason for
networking may be the supply of
applications software to a number
of users or to allow them access to
important shared documents.
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Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Networks - LANs
• A Local Area Network is a network of computers that are all
situated close together for example in a room or building. Since
the distance between computers is relatively small wire cables
are frequently used to connect the computers together. LANs
are usually set up to allow users to share data, communicate and
share expensive peripherals.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Networks - LANs
Network
Type
LAN
Transmission
Media
•
•
•
•
•
3
Coaxial cable
Shielded Twisted Pair
(STP)
Unshielded Twisted
Pair (UTP)
Fibre optic
Wireless
Bandwidth
Between 10Mbps
and 100Mbps
Geographical
Spread
Up to 500 metres
Functions




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Computer Systems
S. McCrossan
Share data
Share peripherals
Communication
Centrally store
data
Higher Grade Computing Studies
5. Networks
Networks - WANs
• This is a network of computers connected across a distance.
Telephone lines, satellites or other communication technology
is required for WANs to work. Most major companies need a
WAN in order to communicate with other branches either
nationally or internationally.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Networks - WANs
Network
Type
WAN
5
Transmission
Media
•
•
•
Fibre optic
Leased line
Wireless
Bandwidth
Between 10Mbps
and 100Mbps
Geographical
Spread
Kilometres
Functions
Share data
Communication
Centrally store data
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Networks - Intranet
• This is a network that allows a private connection access to
Internet services. This usually happens within a particular
company or organisation. Authorised users only are allowed to
access these services and this makes the network relatively
secure. It allows secure email communication and the
distribution of information similar to the World Wide Web.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Networks - Intranet
Network
Type
Intranet
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Transmission
Media
•
•
•
Fibre optic
Leased line
Wireless
Bandwidth
Between 10Mbps
and 100Mbps
Geographical
Spread
Kilometres
Functions
•share data
•share peripherals
•shop, bank, travel,
etc.
•communication
•centrally store data
•advertise
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Networks - Internet
• This is the most common example of a WAN. It uses
telecommunications to transfer data between computers and
distribute information. The World Wide Web (WWW) is a
collection of information held on the Internet. The WWW is
made up of millions of documents called web pages and these
pages are available to any user of the Internet.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Networks - Internet
Network
Type
Internet
9
Transmission
Media
•
•
•
Fibre optic
Leased line
Wireless
Bandwidth
Between 10Mbps
and 100Mbps
Geographical
Spread
Kilometres
Functions
•share data
•share peripherals
•communication
•centrally store data
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Mainframe Computer
• A mainframe computer system has very fast
powerful multiple processors, large fast memory
and backing storage systems and the ability to
support many network terminals at the same time.
• Terminals usually consist of a keyboard
and monitor only and rely on the mainframe
to carry out all the processing and backing
storage required.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Network of Computers
• Most computer networks have stations (computers) that can
work efficiently on their own without the aid of a mainframe.
These networks usually consist of desktop computers being
linked together.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Client Server Networks
• Servers are powerful computers used to carry out various
tasks across the network. Clients are computers that form the
network. The user logs in to the server from the clients
(username and password) and is permitted access to some
resources on the network and denied access to others.
• Servers can
have a variety of
functions ....
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Client Server Networks
• File server
This provides a central disk storage area for any users across
the network. The file server stores users files separately.
Users can then access their files from any workstation on the
network.
• Web server
A computer connected to the Internet that stores and
distributes Web pages upon request to users on the network.
The "server" is actually a software program running on the
computer .
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Client Server Networks
• Print server
This computer allows the management of printing across the
network. It uses a spooler to store users' files and can provide
a queuing facility with prioritising if necessary.
• CD-ROM server
This server allows all workstations across the network to
obtain data from CD-ROM disks.
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Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Client Server Networks
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Network Type
Advantages
Disadvantages
Client Server
•Backups of data stored on servers
can be carried out regularly.
•All shared files are stored on
servers which means data is up to
date and correct.
•Security is controlled more easily
due to the central storage of data and
setting up of users’ access rights.
•Servers can fail and hence stop data,
applications, etc, being shared across
the network.
•Servers are expensive to buy.
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Peer-to-Peer Network
• In a peer-to-peer network
there are no dedicated servers
among the computers. All of
the computers on the network
handle security and
administration for themselves.
The users must make the
decisions about who gets
access to what.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Peer-to-Peer Network
• Security on a peer-to-peer network is not very powerful. So
if you have security concerns go for something you can
control (like a server). Because the users will be required to
give access to folders, they can choose to not require
passwords.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Peer-to-Peer Network
Network Type
Peer-to-peer
Advantages



No need to pay for servers
No or little network congestion
due to smaller number of users
Network can still function
if any clients fail to work
on the network
Disadvantages




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No central storage of files
Security across the network is
poor since it is not centrally
controlled
Backups of network data is
difficult since there is no central
storage
Each client on the network has
equal rights
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Network Topology
• The design of a network is called its topology.
• A node is any device on the network, e.g. workstation
(computer), server, printer.
• A channel is the path over which the data is transmitted
between computers, e.g. telecommunications links, wireless
connection, fibre-optics or twisted pair copper cables.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Network Topology
• Mesh
• Ring
• Bus
• Star
= Node
= Channel
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Network Topology
TYPE OF
NETWORK
Mesh
ADVANTAGE
• Fault in one
DISADVANTAGE
• Lots of wiring.
channel doesn't
affect network messages rerouted.
• Multiple
transmissions can
occur at the same
time.
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AFFECT ON
PERFORMANCE
• Excellent
performance
• Expensive
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Network Topology
TYPE OF
NETWORK
Star
ADVANTAGE
DISADVANTAGE
between any 2
nodes.
• Fault in the
central node
means network is
unusable.
• Easy expansion.
• Congestion at
• Short path
central node.
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AFFECT ON
PERFORMANCE
• Control
computer gives
more robust
network but
slows down
communication
between nodes
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Network Topology
TYPE OF
NETWORK
Bus
ADVANTAGE
• Fault in one
station has no
effect on rest of
network.
• Very easy to
DISADVANTAGE
• All stations use
the same channel
- each station has
to compete for
the central
channel.
AFFECT ON
PERFORMANCE
• Instant access
but high rate of
data crash.
expand.
• Cheap
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•Central channel
breaks – network
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fails.
Computer Systems
S. McCrossan
Higher Grade Computing Studies
5. Networks
Network Topology
TYPE OF
NETWORK
Ring
ADVANTAGE
• Control system
in charge of
transmissions.
• Stations
guaranteed
access to
transmissions.
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DISADVANTAGE
• Additional
expense for
control software
and system.
• May have to
wait to transmit.
AFFECT ON
PERFORMANCE
• Network down
to add new
station but
thereafter, few if
any data crashes.
Higher Computing
Computer Systems
S. McCrossan