Chapter 4_ Networks and Effects of using them.pptx

IGCSE chapter 4

1. Chapter 4: Networks and Effects of using them ICT 0417 ‹#›

2. Networks A network connects computers and other digital devices together and allows them to share data and resources. Networks allow the use of following: Computer-to-computer communication. Computers communicating with devices as a printers, mice and keyboards. Mobile phones. Smart televisions. Tablets and media players downloading videos and music and playing them through external devices such as speakers and digital projectors.

3. Network Types

4. It enables a group of computers that are in close proximity to each other to be networked. Typically, a LAN would be used in a school, in an office or at home. A LAN is useful because it allows resources such as files, printers, games and other software applications to be shared by the computers on the network. There are two ways: By using cables that have to be routed through the building. By using radio waves so that no cables are required. This is called a wireless local area network or WLAN .

5. An advantage of a WLAN over a cable LAN is that: It allows users to move around the area with their devices and remain connected. It lets one or more people to connect their mobile devices such as laptops, mobile phones, tablets, media players, speakers and printers. Wi t h a cable LAN: one would have to log off, remove the cable, plug the cable in somewhere else and log in again.

6. It is a network that connects separate LANs over a large geographical area. WAN connects cities, a country or many countries. A WAN ensures that computers in one location can communicate with computers and users in other locations. The internet is a huge wide area network. The separate networks are connected by cables running through the world under the ground and under the sea and by satellite communications.

7. Data Packets When devices transmit data across the internet, the data is broken down into small pieces called data packets. Packet is a small, formatted unit of data that is transmitted across a network. The packets are sent separately, and then joined up at the end so that the message is complete. Rules are needed so that all the computers on the network work together.

8. Parts of Data Packets Header: This contains the addresses of the source and destination, and also the position of the packet in the complete message file. Body (Payload): This contains part of the complete message/file. Footer (Trailer): This informs the receiving device that it has reached the end of the packet. The footer can also be used for error checking to make sure the packet has been delivered intact.

9. Router Routers allow different networks to communicate. It is used to route data packets from one packet to another network, based on IP address. Routers are used in the home to connect the home network to the internet. They issues internet protocol (IP) address to devices on a network. The addresses can be static or dynamic . (Static IP addresses are created by the user themselves, while dynamic IP addresses are issued by DHCP (Dynamic Host Configuration Protocol). Routers transmit incoming pages, streamed audio, etc. to the correct computer network.

10. How Routers Work When data is received at one port of a router, it inspects the IP address and determines whether the packet is meant for its own network or another network. If the data packet is meant for its own network, then the data packet is routed to the local switch or hub. Otherwise, the data packet is transmitted to a different router (external network)

11. Routers consult a routing table (stored on the router’s RAM) to route a packet to it destination. The routing table contains router’s immediate network and information about the other routers in its immediate vicinity. Routers, do not store MAC addresses of devices, only IP address.

12. Demo

13. Many modern broadband ‘routers’ actually combine the functions of a router and a switch - this means that they store MAC addresses and IP addresses to enable data packets to be sent to the correct network and then to the correct device on the network. ❗❗❗❗❗❗❗❗

14. Common Network Devices Network Interface Card Hub Bridges Switches

15. Network Interface (NIC) It is a component that connects a computer to a network. It turns binary data into an electrical signal that allows that allow data packets to travel to and from the computer to the network. NIC is usually integrated into the motherboard on most modern computers. Network interface cards and adapters support both wired and wireless network connections. Each NIC is given a unique hardwired (hard-coded) media access control (MAC) address at the manufacturing stage. Media access control (MAC) address is a number that uniquely identifies a device when it is connected to a network. The MAC addresses enables data on a network to be sent to the correct computer.

16. Hubs A network hub enables wired devices to connect to each other in a local area network. A hub takes data packet at one port and broadcast it to every device connected to it.

17. How Hubs Work? All of the computers on the network plug into a port on the hub using a cache. When a message is received through the cable from one computer, the hub transmits ( broadcast ) it to all of the other computers. Hubs are “dumb” and cannot learn the addresses of the different devices on a network. Hubs only allow one device at a time to transmit messages.

18. Demo

19. Switches A network switch handles messages more intelligently than a hub by inspecting the MAC address of the device to which they should be sent. The switch knows the addresses of the different devices on the network and only sends the message to the correct device. A switch stores the MAC addresses of all devices on the network in a look-up table. Using the look-up table, a switch matches the MAC address of an incoming data packet arriving at one its ports, and directs it to the correct device.

20. Demo

21. Switches vs Hubs Both a hub and a switch are used to connect devices in a LAN. Both hubs and switches use data packets. Hubs send data packets to every device on the network; whereas switches send data packets to a specific device only. Security is lower with hubs than with switches. A switch uses a look-up table to determine the destination device. Switches use MAC addresses to locate the destination device.

22. Bridge Bridges are devices that connect one LAN to another LAN that uses the same protocol (communication rules). They are often used to connect together different parts of a LAN so that they can function as a single LAN.

23. Wi-Fi and Bluetooth

24. Wireless Fidelity (Wi-Fi) It is a technology that allows devices to connect to the internet or communicate wirelessly within a local area network (LAN). It uses radio frequency (RF) waves to transmit data between devices. It is used in home for connecting mobile phones, smart speakers, tablets, laptops and gaming consoles to the internet. There is no need for network cables all around the house.

25. Bluetooth It is a method of communication based upon radio waves, but it is for devices to exchange information and data. Bluetooth connectivity enables two nearby devices to pair with each other and share packets of data without the need for wires. Bluetooth technology includes: h ands -free phone calls whilst driving wireless headphones remote speakers

26. Similarities Wireless Use radio waves Creates local connection Frequency of signal are similar

27. Differences Wi-Fi Bluetooth Has a range of up to 100 meters Has a range of 10 meters Devices cannot communicate directly Devices can communicate directly Many users can be supported (depends on the router being used) Fewer users can be supported (usually 7) A high level of security (wireless equivalent privacy) and (Wi-Fi protected access) A lower level of security (key matching encryption) Fast data transfer Low data transfer

28. Cloud Computing It is the delivery of computer services over the internet. It is a method of data storage where data is stored on remote servers. They are called servers because they serve these services to the users.

29. There may be thousands of servers in many different locations. Files, data, documents, images, music and videos are stored on these servers in a remote location. A user can purchase space on an external server located somewhere in the world, and access it via the world wide web. The server is connected to the internet and can be downloaded from and uploaded to as the user requiress. The same data is stored on more than one server in case of maintenance or repair, allowing clients to access data at any time. This is known as data redundancy. Cloud computing allows users to access and use applications, such as word processors and spreadsheets, stored on remote servers.

30. Advantages Lower maintenance costs. Data will be secure if there is a fire or other problem at the site. Software does not have to be “bought” and businesses only have to pay for those parts that they need to use (software as a service (SaaS)). As long as they have internet access, employees can work from anywhere in the world and even from home, reducing the need for office space. Many users can access the data and collaborate with each other from anywhere in the world.

31. Disa dvantages Internet access is required. Download and upload speeds can be affected by the internet connection. The organisation has less control and is reliant on the providers to maintain access and update the software but some organisations are building their own ‘private’ clouds. The providers’ servers may be targeted by hackers.

32. Common Network Environments The largest network environment is the internet. There are also smaller network environments, called: intranets extranets

33. Internet It is a global of interconnected computer networks that spans the globe. Any computing device can access this network, making use of an ISP that act as a gateway to the internet. It uses a set of rules or protocols called TCP/IP to send data packets across the internet . The internet provides a number of different services, with the main one being the world wide web (WWW). Websites uses hypertext transfer protocol (HTTP) Other services provided by the internet includes: Data transfer, email, music and video streaming

34. Intranet It is a private computer network within an organisation such as school or a company which uses internet technology. It is separate from the global internet and cannot be accessed by outside users. Users of an intranet sign into the system with a username and password. An intranet contains web pages about the organisation containing newsletters, health and safety policies, etc.

35. Ex tranet It is a network connection that establish a remote connection to a secure server on a LAN or WAN. It allows users from other organisation to use it for specific purposes. E.g: hospital intranets that allow access to community doctors to book appointments for patients or a manufacturing company that allows access to distributors for ordering and pricing information. A virtual private network (VPN) enables a computer and the server to exchange a secret encryption key, which scrambles the data transfer.

36. Similarities: Internet, Intranet and Extranet They provide services that use different protocols or rules, such as web page access and emails. They require connections to servers. They are either WANs or LANs.

37. Differences : Internet, Intranet and Extranet The internet simply needs a connection through an internet service provider, whereas an intranet or extranet also require a username and password. The internet is publicly available to a range of devices, whereas an intranet and extranet are private and for authorized users only. Extranets often require encrypted access to servers due to the distance between the user and the network, whereas an intranet tends to be accessible within or nearby a building.

38. Network Issues and Communication All networks must be kept secure so that data is not corrupted or stolen. All online systems can be hacked and data can be stolen when it is stored or transmitted. Networks should be protected against data interception and theft. Data traffic in LANs and WANs can be intercepted. Hackers analysers or ‘packet sniffers’ to intercept the packet, which are then analysed and their data is decoded.