igcse ict ao2.4 notes

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  • Created on: 11-05-13 19:31
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Amy Cole 10T
Section 2.4: Computer networks
(a) Network equipment
a. Describe a router and its purpose
A router is a network device that connects together two or more networks.
A common use of a router is to join a home or business network (LAN) to the Internet (WAN).
The router will typically have the Internet cable plugged into it, as well as a cable, or cables to computers on
the LAN.
Alternatively, the LAN connection might be wireless (WiFi), making the device a wireless router. (A wireless
router is actually a router and wireless switch combined)
b. Describe the use of WIFI and Bluetooth in networks
Connecting a wireless keyboard to a computer
Connecting a wireless mouse to a computer
Using a wireless headset with a mobile phone
Printing wirelessly from a computer or PDA
Transferring data / music from a computer to an MP3 player
Transferring photos from a phone / camera to another device
Synchronising calendars on a PDA and a computer
WiFi generally refers to the wireless system used by computers to connect to other computers (e.g. to create a
LAN). WiFi effectively replaces network cables. WiFi has a long range (50100m)
Bluetooth is a wireless technology used to connect computers to outside devices (e.g. keyboard, mouse,
camera, etc). Bluetooth replaces device cables (e.g. USB). Bluetooth has a short range (25m).
c. Describe how to set up a small network involving access to the internet, understanding the
need to set up the use of a browser, email and an ISP
You would need to buy some hardware:
One or more switches / hubs to link devices together
Network cables to connect devices to the switch, etc.
A separate wireless access point (or this could be part of the switch) to allow wireless devices (e.g.
laptops or smartphones) to join the network
A router to connect your LAN to the Internet (WAN)
A firewall to protect your network from hackers
Possibly a bridge if you already have a section of network and you want your new network to connect
to it

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Amy Cole 10T
Server(s) to manage network functions such as network security, network file storage, shared
resources (such as printers)
You would need to organise some other things:
Set up an account with an Internet Service Provider (ISP)
Get an Internet connection installed from the ISP to your location
Configure various bits of hardware and software so that everything worked with the network
d.…read more

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Amy Cole 10T
A hub is a `dumb' device: if it receives a message, it sends it to every computer on the network. This means
that hubbased networks are not very secure everyone can listen in to communications.
Hubs are pretty much obsolete now (you can't buy them any more), having been superseded by cheap switches.
A switch, like a hub, is a device that connects a number of computers together to make a LAN.…read more

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Amy Cole 10T
ii. Wireless Local Area Network
A wireless LAN (WLAN) is a LAN that uses radio signals (WiFi) to connect computers instead of cables.
At the centre of the WLAN is a wireless switch or router a small box with one or two antennas sticking out
the back used for sending and receiving data to the computers. (Most laptops have a wireless antenna built
into the case.…read more

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Amy Cole 10T
The Internet connects millions of people, and thousands of businesses, governments, schools, universities and
other organisations.
What Can We Use the Internet For?
The Internet provides the network connections that link computers together.…read more

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Amy Cole 10T
Communicate with other network users (email, instant messaging, videoconferencing, etc.)
Store data centrally (using a file server) for ease of access and backup
Keep all of our settings centrally so we can use any workstation
In particular, if we use a computer connected to The Internet, we can...
Make use of online services such as shopping (ecommerce) or banking
Get access to a huge range of information for research
Access different forms of entertainment (games, video, etc.)
Join online communities (e.g.…read more

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Amy Cole 10T
Video conferencing Can be long distance. Need a strong internet connection.
You can see the other people. Need additional hardware such as webcams,
Done in real time. large monitors, microphones and speakers.
Can see reactions, facial expressions and There can be lag.
body language. The sound and picture quality is often poor
Uses echo cancellation software which unless expensive hardware is used.
synchronises communication.…read more

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Amy Cole 10T
For this to be effective passwords must be chosen that are not easy to guess. Passwords should be a random
combination of lowercase letters, uppercase letters and numbers (and symbols if this is allowed):
`Weak' passwords: password, 123456, david, 27dec1992
`Strong' passwords: s63gRdd1, G66ew$dQ, gdr298783X
Some computer systems replace the typing of usernames and passwords with other forms of user
identification such as ID cards, fingerprint readers, voiceprint recognition, etc.…read more

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Now that Bob has a copy of the key, each time Alice needs to send him a message she starts by encrypting it
using special encryption software and the secret key.
The encrypted message now looks like a jumble of random letters and numbers.
Alice then sends the encrypted message to Bob.
She can use a public network like the Internet, since, even if it gets stolen, the encrypted message cannot be
read or understood without the key.…read more


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