1. Networks and the effects of using them

2. Network devices

3. Modems (modulator demodulator)
A device that converts a computer’s digital signal into an analogue signal for transmission over an existing telephone line.
Used to allow computers to connect to networks over a long distance using the existing telephone networks.

4. Hubs
Hardware devices that can have a number of devices or computers connected to them.
Used to take any data packet (a group of data being transmitted) received at one of its ports and broadcast it to every computer in the network.
Often used to connect together a number of devices to form a LAN-for example, a star network

5. Switches
Similar to hubs but are more efficient in the way that they distribute data packets.
Check the data packet received and works out its destination address and sends the data to the appropriate computer(s) only.
Each device or computer on a network has a media access control (MAC) address that uniquely identifies it.

6. Bridge
Devices that control one LAN to another LAN that used the same protocol (communication rules)
Used to connect together different parts of a LAN so that they can distribute as a single LAN.

7. Router
Enable data packets to be routed between the different networks, for example to join a LAN to a wide area network (WAN).
Have an internet cable plugged into it and several cables connecting to computers and other devices on the LAN.
Broadband routers sit behind a firewall which protects the computers on a network. The router transmits internet and transmission protocols between two networks and allows private networks to be connected together.

8. Data packets
The data is carried in the packet according to which protocol is used.
-the identify number of each packet
This info allows the router to route a packet across a network to its correct destination and allows the data packets to be reassembled in their correct order.
Usually contain:
-Some form of header to identify the data packets
-Sender’s IP address
-Receiver’s IP address
-How many data packets make up the whole message.

9. Gateway
A network point (or node) that acts as an entrance to another network.
A key point for data on its way to or from the other network

10. Network interface card (NIC)
Is needed to allow a device to connect to a network.
Usually part of the device hardware and frequently contains the MAC address generated at the manufacturing stage.

11. Networks cables
Even though many computer system use Wi-Fi, network cables Wi-Fi, network cable are still used because:
-Faster data transfer rates
-Can be more secure than a wireless networks

12. Internet protocol (IP) and media access control (MAC) addresses

13. Each device on the internet is given a unique address known as its internet protocol (IP) address.
A MAC address is a unique number that identifies a device connected to the internet

14. Differences between IP addresses and MAC addresses
Gives the location of a device on the internet
Identifies the device connected to the internet

15. Wi-Fi and Bluetooth
Both Wi-Fi and Bluetooth offer wireless communication between devices. They both use radio frequencies as the carrier of data transmission.

16. Wi-Fi
A wireless transmitter (WAP) receives info from a network via its connection. This transmitter converts the info into radio waves and then transmits them.
A device(e.g. a computer) receives the radio waves via an installed wireless adaptor which allows it to download the info from the data resource. This, of course, works in the reverse when the device wishes to transmit data over the network.
Wi-Fi offers much faster data transfer rates, better range and security than Bluetooth.

17. Bluetooth
Bluetooth sends and receives radio waves in a band of 79 different frequencies(known as channels). These are all centered on a 2.45 GHz frequency.
Devices using the Bluetooth automatically detect and connect to each other, but they don’t interfere with the other devices since each communicating pair uses a different channel
When a device wants to communicate, it picks one of the 79 channels at random. If the channel is already being used, it randomly picks another channel
(a.k.a spread-spectrum frequency hopping)
Useful: when transferring data between two or more devices that are close together, for low-bandwidth applications

18. Differences between Wi-Fi and Bluetooth
Transmission frequency: 2.4, 3.6, 5.0 GHz
Max data transfer rate: 250 Mbits/second
Max effective range: 100m
Max number of devices connected: depends on the router used (one or many)
Type of data transmission security: WEP (wireless equivalent privacy) and WPA (Wi-Fi protected access)
Transmission frequency: 2.4 GHz
Max data transfer rate: 25 Mbits/second
Max effective range: 30m
Max number of devices connected:7
Type of data transmission security: key matching encryption

19. How to set up and configure a small network
Setup an IP account if internet is required
Set up the system
Configure all the hardware and software
Setting up privileges so each user can only access their own area
Ensure high-speed broadband connection exists if needed internet
Put all software in one server
Set up a network-manager-level of privilege do that they can monitor network usage, change passwords, etc

20. Local area network (LAN)
These systems are usually within one building/ not very far from each other.
Consists of a number of computers and devices(for ex, printers) that are connected to hubs /switches. One of the hubs/switches will usually be connected to a router and a modem to allow the LAN to connect to the internet, in doing so it then becomes part of a WAN

21. Advantages: -ease of communication between
the users.
-a network administrator to
control and monitor all aspects
of the network
Disadvantages: -easier spread of viruses
throughout the whole
network
-if the main server breaks
breaks down, in most cases
the network’ll no longer function

22. Wide area network (WAN)
Are used where the computers or networks are situated a long distance from each other
If a number of LANs are joined together using a router or modem, then they can form a WAN. Ex: the internet and the network of the ATMs used by the banks

23. Wireless LANs (WLANs)
Are similar to LANs but they provide wireless network communications over fairly short distances using radio or infrared signals
Devices, a.k.a access points (APs), are connected into the wired network at fixed locations. Because of the limited range, most commercial LANs need several APs to permit uninterrupted wireless communications. The APs use either spread spectrum technology (wideband radio frequency with a range of 30-50m) or infrared (has a very short range and easily blocked)

24. Advantages:
Disadvantages:
-As there is no cabling there is a safety improvement and increased flexibility (since the user no longer has to remain at their desk)
-Security can be a big issue since anyone with a WLAN-enabled laptop can access a network if it can pick up a signal
-Data transfer rate is slower than in a wired LAN
-Adding new computers and devices is very easy, costs are reduced since extra cabling isn’t needed.

25. Accessing the internet

26. Mobile phones and tablets
Portable, can be used almost everywhere provided a mobile phone network signal can be accessed
Expensive to use if the Wi-Fi hot spot is not available
Display are small
Keyboards are small
People is more likely to have their phones at all times
Not all websites are mobile-friendly
Signal less likely to be as stable or reliable as a wired system
Easier to use a phone while on the move

27. Laptops More mobile than desktops Screen size is smaller than desktops
Touchpads are not as easy to use as a mouse but easier than phones
Processors are not as powerful as desktops’ so access speed is not as quick
Keyboards are not as easy to use as desktops but are better than phones

28. Desktop computers More powerful/faster processor than other devices
Full-size keyboard and pointing devices make web page navigation much easier
Have more stable and reliable internet connection since they use a wired system rather than Wi-Fi
Not portable
Require expensive ‘dongles’ to access the phone network
Large screen

29. Should the internet be policed?
Arguments in favor of some control:
-Prevent illegal info to be posted
-Easier to find info that can have serious consequences
-Prevent kids and other vulnerable groups from being subjected to undesirable sites
Arguments against some control:
-Info posted on webs is already available form the other sources
-Expensive to ‘police’ all sites and users would have to pick up the bill
-Difficult to enforce the rules and regulations on a global scale

30. Inappropriate sites and the accuracy of info
Three aspects to consider when looking at the quality of info found on a search engine: -Reliability of info -Undesirability of certain websites -Security issues

31. Reliability of info
Info on the internet is more likely to be up to date than in books
Easier to get info from websites
Large amount of info on the internet that is easier to locate than using books
Info could also be incorrect since it doesn’t go through any checking

32. Undesirability of certain websites
Risk of finding undesirable webs
Risk of connecting to webs that are not genuine, which could lead to problems
Security risks

33. Security issues Passwords are used when: -accessing email accounts
-carrying out online banking
-accessing social networking sites
It’s important that passwords are protected and here are some ways:
-run anti-spyware software
-change passwords on a regular basic
-passwords should not be easy to break or guess

34. Authentication
Is used to verify that data comes from a secure and trusted source.
User IDs and passwords are authentication technique. Some forms of authentication include:
-digital certificates
-biometrics
-magnetic stripe cards/id cards/passports

35. Antivirus software
Antivirus software will constantly check for virus attacks
Common features :
-check software/files before run or loaded
-compare a possible virus against a database of known viruses
-carry out heuristic checking- checking of software for types of behavior that could indicate a possible virus
-files that are affected are put into quarantine that: allows the virus to be automatically deleted or allows user to make decision
-antivirus software needs to be update since new viruses are constantly being found

36. Avoiding viruses when accessing the internet
Avoid unknown or suspicious-looking webs
Look for the security indicators as https or the padlock symbol
Not advisable to open s /attachments from unknown sources

37. Viruses from hardware devices
It’s possible to pick up viruses from any device plugged into your computer

38. Data protection acts
Guidelines about how stop data from being obtained unlawfully:
-don’t leave personal info on a desk
-lock cabinets at the end of the day
-log off your computer if away from your desk
-use hard-to-guess password and user ids

39. Network communication

40. Faxes Two basic ways to send a fax: A physical fax
A electronic fax (modern way)
The only difference is electronic faxing is always associated with an address and a fax number

41. Emails Useful when sending attachments
Can be sent to or from any device connected to the internet

42. Video conferencing Basic hardwares: -webcams -large monitors
-microphones
-speakers
Advantages:
-possible to hold meetings at short notices
-not travelling physically reduces costs

43. Audio conferencing
Equipment needed: telephone/internet phone/computer with built-in speakers and microphone

44. Web conferencing
Uses the internet to permit conferencing to take place
Multiple computers are used
Only needed computer with high-speed and stable internet connection
To carry out web conferencing, users have to use an application or website from the conference organizer.