1 computers, part of your - hselspark
TRANSCRIPT
Computers,
part of your
life
Grade 11
1
Local area
networks
2 Module 2.1
A computer network is a group of computing devices (e.g. computers, printers,
scanners, etc.)
that are connected to each other by means of some
communication medium (cable or wireless)
in order to communicate with each other.
3 Computer network –
definition
Types of networks
PAN – organised around an individual
HAN – network in a home environment
LAN – small area, generally in one building
Internet – worldwide computer network
Intranet – organisation’s private network
4
Classified according to the area that they cover
Computers and peripherals
Client
desktop laptop tablet smartphone
Basic components of a
network – Hardware5
Computers and peripherals
Server
file server
email server
internet / proxy server
web server
print server
database server
6Basic components of a
network – Hardware
How do you
know you are
connected
to a network?
Presence of extra
(logical) drives such
as U:, V: and T:
Presence of other
computers in
Network
Access to devices (e.g. printers) not
directly attached to
the computer
Indicator showing
network activity in
the notification area
7
8
Network Interface Controller
NIC – to connect device to
network via cable
Wireless adapter
and NIC –both built
into device
Switch
To connect computers in a
network – so communication
can occur
Basic components of a
network – Hardware
9
Basic components of
a network
LAN (Local area network) a network that covers a small
area such as a classroom,
school, office building or
campus.
In a LAN the infrastructure
needed to connect the
computers in a network, is the
private property of the
institution – no service provider
(e.g. Telkom) is needed to
establish the network.
10 LAN – definition
WLAN (Wireless local area
network) a LAN connected via a wireless
communication medium.
11 WLAN – definition
Image:
http://www.telenor.com/wp-content/uploads/2010/12/WLAN-SIM-no-
text.jpg
PAN (Personal area network) devices such as tablets
and smart phones are
connected to each other
over a small area
(±10 m radius).
Usually via Bluetooth.
12 PAN – definition
Image:
http://www.brunel.ac.uk/__data/assets/image/0007/197134/PA
N.gif
HAN (Home area network) devices connected in a
small area such as a house,
usually by means of
radio waves (WiFi).
13 HAN – definitions
Image:
http://www.att.com/Common/DSL/center/images/connected_ho
use.gif
14
WLAN advantages compared to LAN
Easier to install
Easier and more practical between
buildings
Easy to add or move computers
Adds mobility – users with mobile devices
Avoids clutter
Basic components of a
network –
Communication methods
Communication
Sharing devices e.g. printers and scanners
Sharing data
Share software
Better security
Easier backup
15 Advantages of a LAN/WLAN
Files stored on central computer – users access from
any computer in network
Files transferred without use of
devices
Software shared by users
Hardware shared by users
Security in network controlled
Single internet connection
shared by users
Easier to keep software up to
date
Software can be
demonstrated or broadcast
to other computers
Internet access monitored
and controlled
16 Advantages of a LAN
Cost – it can be expensive to set up and maintain a LAN.
If the LAN is not well planned, it can become even more expensive.
Viruses – a computer virus can spread very easily in a network if security measures are not in place.
Data security can be a problem, because many users have access to data in a network.
17 Disadvantages of a LAN
Network administrator – sometimes an administrator is needed to manage a network. Thus the cost of keeping the network up to date increase.
Signal weakening – the length of cables restrict the size of a LAN. If the cables are too long (more than 100m), the signal strength decrease.
The communication speed is determined by the communication medium.
If the server fails, the whole network is out of order.
18 Disadvantages of a LAN
Can be expensive to install
and maintain
Network administrator
often needed to manage
Network security must be
maintained
If file server faulty, no one can access their files
Security can be compromised – easier
for unauthorised persons to gain access
Performance can decrease as number of computers connected increases
Signal loss or interference due to
electrical interference
19
Additional potential disadvantages
if wireless (WLAN)
Disadvantages of a LAN
20
Communication methods
Cables
UTP (Unshielded Twisted Pair)
Fibre optic cable
Wireless
Wireless access points
Wireless enabled /
wireless adaptor
Basic components of a
network
21
UTP cable
• Only spans certain
distance – signal loss
• Can be ‘eavesdropped’
on
• Affected by electrical
sources
• Uses electrical signals to
transmit data
Fibre cable
• Spans much longer
distances
• Immune to
‘eavesdropping’
• Not affected by electrical
sources
• Uses light signals to
transmit data
• Faster data transmission
than UTP cable
Basic components of a
network
Maximum speed depends on cabling
and devices (switches and NICs)
802.11 specification – wireless adapter(802.11g and 802.11n – different speeds)
WLAN is slower than a cabled LAN
22 Basic components of a
network
Data transmission speed
Rate at which data is transferred
over the media used
E.g. 100 Mbps / 1000 Mbps
Workstations (clients)
The computers used by the users of
the network and are connected to
the server. They usually use the
recourses and services provided by
the server.
Examples: desktop computers,
laptops, tablets, smart phones.
23 Computer devices (nodes)
Servers
Computers with powerful capabilities:
fast and powerful processor, large
amount of RAM and very big hard
disk space.
All the workstations and other devices
are connected to the server.
The server provides services used by the clients.
24 Computer devices (nodes)
Types of servers File server – stores data used by the clients.
No data is supposed to be stored on the client computer.
Print server – provides access to the printers in the network and manage them.
Proxy server – allows safe access to the internet.
e-mail server – used to manage e-mail facilities in the network.
Web server – used to host websites.
25 Computer devices (nodes)
Communication media
A communication medium is used to
transfer data from one device to
another.
26 Communication media
Twisted pair (UTP)Used in a LAN in together with a switch.
RJ45 connector is used to connect to the device.
Consists of copper wires.
Signal strength decrease if longer than 100 m.
Is influenced by electromagnetic interference. Can therefore not be used in areas where large electric machinery are used.
27 Communication media
Fibre optic cables Transfer data in the form of light signals through very fine glass
strands (fibre glass) or plastic fibre.
Very large amounts of data can be transferred at a very large
transfer speed over very large distances.
Can be used in areas where there are electromagnetic signals.
Expensive and difficult to install.
28 Communication media
Wireless (Bluetooth and WiFi) High frequency radio waves are used to transfer data.
Access points are needed to send the radio waves needed for communication. An access point may, however, be a connection to an ADSL telephone line, which is not wireless. It may also be a device making use of cellular services, e.g. GPRS, 3G, HSDPA, EDGE, etc.
Bluetooth – communication between personal devices over a very short area. Used to build a PAN.
WiFi – communication via an access point over a relatively small area (±35 m radius indoors and 100m outdoors).
Signals can travel through solid objects, e.g. walls.
29 Communication media
30 Network interface card (NIC)
Needed to connect the network device with the
communication medium.
Used to translate data from the way the device
“understands” it to the way the communication medium can
transfers it, and visa versa.
Can be built into the motherboard of the computer/laptop.
Different types of NIC needed for data transfer over cables
(RJ45-connector needed) and wireless transmission (aerial
needed to send and receive radio signals).
Most portable devices are equipped with a wireless NIC.
Laptops are also equipped with an Ethernet NIC for
connection with UTP cables.
31 Network interface card (NIC)
Device needed to set up a LAN with UTP cables.
Central connection point for all devices in the
network.
32 Switch
The system program needed to set up the
communication between the devices and control
access to the network, e.g. user rights and other
security measurements.
Most operating systems, e.g. Windows 7 and Windows
8, have built-in network facilities.
33 Network software
Basic components of a
network –
Network software
34
Software that controls communication and security in a network
Most operating systems have built-innetworking capabilities
For larger networks ‘Server’ editions of the operating system are installed on the servers
Advantages and
disadvantages of a LAN35
36 Basic network security
Rules to ensure the security of a network –
preventing unauthorised access to
information and network misuse
Access to confidential files must be restricted
In a school situation – important that learners do
not have access to tests before they are written
A username and password are used to gain
access to network resources
Choose a password known only to you
Keep your password secret!
At least 8 characters long
Mixture of upper and lowercase letters, numbers
and special characters
Do not use anything that is easy to guess about you
Do not use passwords that follow a pattern on the
keyboard such as ‘asdf’ or ‘1234’
Change password every 2 months or so
Do not use same password for more than one site
37
Example of a good password
Q1w2E3R4t%y
Choosing and managing passwords
Need for acceptable, ethical practices
Acceptable Use Policy (AUP) outlines the
rights and responsibilities of users, especially
in networked environments
AUP lists what users may and may not do on
the network
Designed to protect both the user and the
business / organisation / school when using
ICT facilities
38 Ethical use of networks
Basic netiquette rules
Restrictions on what may be accessed online
Restrictions on amount of data downloaded from internet
Importance of responsible ethical / legal / safe practices
Details on where and when portable storage devices may
be used
Restrictions on installing hardware and software
Procedures for victims of identity theft, malware, cyber-bullying, cyber-stalking
Consequences of violating conditions set out in AUP
39 What should be included in AUP
Written module activity40