1. Networks and effects of using them
Unit 4
Networks and effects of using them

2. What is a network?
A network is a group of two or more computer systems linked together.

3. Hubs Hardware device Can have a number of devices connected to them
Usually used to form a LAN
Main task is to take any data packet - group of data being transmitted)
Not very secure and/or efficient

4. Modems Short for “Modulator demodulator”
Converts digital into analogue over an existing telephone line
Reverse process
Used to allow computer to connect to network

5. Switches Similar to hub but more efficient
Connect computer together to form a LAN
Checks data packet received and works out its destination and sends data to appropriate computer
MAC(media access control)=address that identifies network

6. Bridge Connect one LAN to another LAN that uses the same protocol
Connect different parts of a LAN so that they function as a single LAN

7. Router WAN (wide area network)
Enable data packets to be routed between the different networks
WAN (wide area network)
One internet cable plugged in, and several cables connecting to computers and other devices on the LAN
Main function is to transmit internet and transmission protocols between two networks
IP= internet protocol

8. Gateway
Network point or node that acts as an entrance to another network
Key point for data on its way to or from other networks

9. Network interference card (NIC)
Needed to allow device to connect to a network (ex. Internet)
Contains MAC address

10. Network cables Instead of Wi-Fi Can be either copper or fiber optics
ADVANTAGES
Faster data transfer rates
Can be more secure than wireless networks

11. IP adress ( internet protocol)
Each device has one
32-bit number
Home computer is given one when it connects to the internet
Only ip adresses that remain uncharged are web servers
Can be used instead of typing in the full URL

12. WIFI Offers wireless communication
Wi-Fi network makes use of radio waves to transmit information across a network.
The computer should include a wireless adapter that will translate data sent into a radio signal.
This same signal will be transmitted, via an antenna, to a decoder known as the router.
Once decoded, the data will be sent to the Internet through a wired Internet connection.
As the wireless network will work as a two-way traffic, the data received from the Internet will also pass through the router to be coded into a radio signal that will be receipted by the computer's wireless adapter. 

13. Bluetooth
The Bluetooth standard, like WiFi, uses the FHSS technique (Frequency-Hopping Spread Spectrum)
which involves splitting the frequency band of GHz into 79 channels (called hops) each 1MHz wide
then transmitting the signal using a sequence of channels known to both the sending and receiving stations. 
Thus, by switching channels as often as 1600 times a second, the Bluetooth standard can avoid interference with other radio signals. 

14. How to set up a small network
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 smart-phones) 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
Server(s) to manage network functions such as networksecurity, network file storage, shared resources (such as printers)

15. How to set up a small network
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

17. Local are networks (LAN)
A local-area network (LAN) is a computer network that spans a relatively small area. Most often, a LAN is confined to a single room, building or group of buildings, however, one LAN can be connected to other LANs over any distance via telephone lines and radio waves.
ADVANTAGES
DISADVANTAGES
Sharing of resources
Spread of viruses
Ease of communication
Slow access
Easy to control
Security risk

18. Wide area networks (WAN)
 WAN is a collection of computers and network resources connected via a network over a geographic area. Wide-Area Networks are commonly connected either through the Internet or special arrangements made with phone companies or other service providers.

19. Wireless LANs (WLAN)
WLAN is a type local network that utilizes radio waves, rather than wires, to transmit data. Today's computers have WLAN built onboard, which means no additional Wi-Fi card needs to be installed.
Access points (AP) are connected into the wired network at fixed locations

20. Accessing the internet

21. Mobile phones and tablets
ADVANTAGES
DISADVANTAGES
Very portable, network signal can be accessed
Expensive if hot-spot is not available
Persons are more likely to carry them
Small display, more difficult to read web pages
Easier to use while on the move
Keboards are small
Not all websites are mobile friendly
Signal less likely to be as stable as wired systems

22. Laptops ADVANTAGES More mobile than desktops
Touchpad is easier to use than phone touchpad
Keyboards are much better than phone keyboards
DISADVANTAGES
Not as large as a desktop
Expensive to access phone networks
Processors are not as powerful as desktop
Slow access speed

23. Desktops computers ADVANTAGES Fast processors Stable internet
All websites are accessable
Use of full-sized keyboard
DISADVANTAGES
Parts are all seperate
Expensive to access phone networks
heavy

24. Network issues and communication

25. Should the internet be policed?
Help prevent illegal material being posted
Prevent children from being subjected
Stop incorrect infos
Already available sources
Expensive
Difficult to enforce rules
Laws already exist

26. Inappropriate sites and the accuracy of information
Three main aspects to consider:
Reliability
Undesirablility
Security issues

27. Reliability Up to date rather than books Easier to get infos
Vast amount of infos
Infos could be incorrect
Risk of information overload

28. Undesirability Risk of finding inppropriate websites
Risk of connecting to websites that are not genuine (real)
Security risk

29. Security issues
Passwords to access account, online banking, social networks
Protect your password!
Anti-spyware software
Change password regularly
Hard to remember

30. Authentication
Used to verify that data comes from a secure source

31. Viruses- Antivirus software
Check software
Compares possible virus against database of known viruses
Carry out heuristic checking(checking behaviour that could indicate virus)
Needs to be kept up to date
Full system checks need to be carried out

32. Avoiding viruses Avoid unknown websites Look for padlock symbols
Look out for odd behaviour in URL
Don´t open s from unknown sources

33. Data protection acts Don´t leave personal infos lying around
Lock filing cabinets
Use passwords and user Ids
Do not leave data on a computer monitor

34. Network communication

35. Faxes Physical fax=machine connected to telephone line.
Allows documents to be sent to another fax machine
Electronic fax=network is required
Saves paper, needs computer, transmissions are sent to an account

36. Email Electronic mail Useful when sending attachments
Available on any device
Require an account
More secure than faxes
No need to print

37. Video conferencing Communication method that uses video and sound
Hardware include: webcam, monitor, microphone, speakers
Agree a time and date
Check if all the hardware is connected and functionable

38. Audio conferencing Meeting via audio
Organiser is given two PINs by phone company
Organiser contacts all participants and inform them of their PIN
Organiser dials conference number
Participants call same conference number to join in, once they get through the have to put in their PIN
Also possible with computer,, makes use of VoIp( Voice over Internet Protocol)