1. ICT Unit 4: Network and the effects of using them

2. Networks

3. What is a network?
A network is two or more computers, or other electronic devices, connected together so that they can exchange data. 

4. Some Network Devices
Modems
Hubs
Switches
Bridge
Router

5. Modem
Modem means ‘modulator demodulator’ and is a device that converts a computer’s digital signal into an analogue signal. It essentially used to allow computers to connect to networks.
Dial-up modems operate at a transmission speeds of about 60 kilobits per second, which is extremely slow by today’s standards ( 60 kilobits= bits)
ADSL (asymmetric digital subscriber line) modems

6. Hubs and Switches
A hub is a device that connects a number of computers together to make a LAN. If it receives a message, it sends to every computers in that network. 
A switch is a device that connects a number of computers together to make a LAN as the same as the hubs. If it receives the message, it would check who it is addressed and send the information to the specific computer. 

7. Bridge
A bridge is a network device that typically links together with two different parts of LAN.

8. Router
A router is a network device that connects together with two or more networks. It’s mostly used to join a home or business network to the internet.

9. Other hardware

10. Gateway
Gateway is a network point ( or node* ) that acts as an entrance to another network. It is a key point for data on its way to or from other networks.
*Node is a connection point, either a redistribution point or an end point for data transmissions.

11. Network Interface Card (NIC)
Any computer that is connected to a network, needs to have NIC. But, some computers such as laptops, they have two kinds of NIC:
One for wired connections
Another for wireless connections.

12. Network cables
Many computers systems use Wi-Fi, network cables are still used because they have the following advantages over Wi-Fi:
Faster data transfer rates
Can be more secure than wireless networks

13. Wi-Fi and Bluetooth

14. Wi-Fi
A wireless transmitter ( WAP ) receives information from a network via its connection. This transmitter converts the received information into radio waves and then transmits them.
Wi-Fi is best suited to operating full- scale networks since it offers much faster data transfer rates, better range and better security.
Wi-Fi hotspots are places where you can access Wi-Fi. They exist in public place such as airports and hotels.

15. Bluetooth
Sends and receives radio waves in a band of 79 different frequencies.
( known as channels).
Devices using Bluetooth automatically detect and connect to each other, but they don’t interfere with other devices since each communicating pair uses a different channel.
Bluetooth creates a secure wireless personal area network ( WPAN ) based on key encryption.

16. Local area networks (LANs) and wide area networks (WANs)

17. Local Area Networks (LAN)
- Advantages for Local area networks (LAN):
The sharing of resources (such as expensive peripherals and applications software)
Communication between users
A network administrator to control and monitor all aspects of the network (e.g. changing passwords, monitoring internet use and so on).
- Disadvantages for Local area networks (LAN):
Easier spread of viruses throughout the whole network
The development of printer queues, which can be frustrating
Slower access to external networks, such as the internet
Increase security risk when compared to stand- alone computers
If the main server breaks down, in most cases the networks will no longer function.

18. Wide Area Networks (WANs)
Are used where computers or networks are situated a long distance from each other geographically.
Advantages for WANs
The organizations can share data quickly even though the distance is far
Transfer data is faster than any other methods
Disadvantages for WANs:
If telecommunication links fail, then communication across a WAN would not be possible.
Viruses can spread very quickly through the networks
Hackers are more likely to attack the servers than LANs

19. Wireless LANs (WLANs)
WLAN is a LAN using radio that uses radio signals (Wi-Fi) without connecting the computers with the cables or wires.
Advantages for WLANs:
Access to WLANs are more flexible than LANs
Users can access to the internet either indoor and outdoor
Wireless access point is also installed in the public areas
Disadvantages for WLANs:
WLANs are slow if there are lots of computers connecting together
The distance of each computers connection is shorter than LANs