L5 Computer Networks PDF

UNIT 2: Computer NETWORKS  Common network terms Common network devices Wi-Fi and Bluetooth Cloud computing (storage) - understanding the need to set up the use of a browser, email and an ISP; - describe other common network devices (including hubs, bridges, switches and proxy servers); ...

UNIT 2: Computer NETWORKS  Common network terms Common network devices Wi-Fi and Bluetooth Cloud computing (storage) - understanding the need to set up the use of a browser, email and an ISP; - describe other common network devices (including hubs, bridges, switches and proxy servers);  WHAT IS A NETWORK? A network is two or more computers, or other electronic devices, connected together so that they can exchange data. For example a network allows computers to share files, users to message each other, a whole room of computers to share a single printer, etc. Network connections between computers are typically created using cables (wires). However, connections can be created using radio signals (wireless / wi-fi), telephone lines (and modems) or even, for very long distances, via satellite links.  WHY USE NETWORKS? Using a computer connected to a network allows us to… Easily share files and data Share resources such as printers and Internet connections Communicate with other network users (e-mail, instant messaging, video-conferencing, etc.) Store data centrally (using a file server) for ease of access and back-up 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 (e-commerce) 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. MySpace, Facebook, Instagram etc.)  WHY NOT USE NETWORKS? Using a computer connected to a network means that… The computer is vulnerable to hackers If the network breaks, many tasks become very difficult Your computer can more easily be attacked by a virus It is costly In particular, if we use a computer connected to The Internet… We have to be careful about revealing personal information We have to be careful to avoid suspect websites that might contain malware We have to be aware that information found on The Internet is not always accurate or reliable CLIENT? SERVER?  COMPUTERS IN A NETWORK Computers connected together to create a network fall into two categories: servers and clients (workstations).~ Clients Client computers, or workstations, are the normal computers that people sit at to get their work done. Servers Servers are special, powerful computers that provide ‘services’ to the client computers on the network. These services might include: Providing a central, common file storage area Sharing hardware such as printers Controlling who can or can’t have access the network Sharing Internet connections Servers are built to be very reliable. This means that they are much more expensive that normal computers. Servers Client The job of a server is to provide services to The job of the client is to provide a the clients on the network. workstation for networks users to use. The services that a server might provide When a user logs in to a client they are include: usually provided with access to: User Authentication a private files storage area File Storage a shared file storage Internet Access the internet and the organisation’s Hardware sharing ( printers, intranet. scanners,etc) Network hardware resources, such as printers and scanners. Network Hardware  Understand how a router works and its purpose Data Packets contain the following information: Header to identify Data Packet. Sender and Receiver's IP address. Number of data packets making up the whole message. Connects network/computers to the internet Connects LANs/networks together Transfers data between networks (Receives and Sends Data Packets) Router can connect to devices using cables or wireless signals. It stores information about which computer is connected to which network  Web Server Web Pages are stored on Web Servers. Webpages have unique IP address & domain names to find/communicate with each other. R Router S R R R Outgoing Data Incoming Data Internet S R Routers direct packets of data across the internet to its destination. R R Everything connected to the internet has an IP Address.  A Hub and a Switch both connect a number of computers together to make a LAN. Hub Switch Smart Device Dumb Device Sends specific packets of data to specific computers Sends data packets to all the workstations on the on the LAN using workstations unique MAC addresses. network which causes network traffic. More secure however more expensive Poor Security Normally used in larger networks found in Only would be suitable for a small home schools, offices etc. networks.  Workstation connect to switch ports. Each Network Card Switch Ports has a unique address (MAC ADDRESS) which switches can 1 2 3 4 use to identify a workstation. 2 2 You always start with Switch Table S S an empty switch table. 1 3 1 3 Work station Mac The switch will learn Address each workstations MAC address when it 1 AA-AA-AA 4 4 sends a packet of 2 BB-BB-BB data across the Sending Packets of Data from Sending Packets of Data from network. 3 Workstation 1 – 2 Workstation 2 – 1 4 The switch will send data packets to all Now the switch table has the MAC address computers because it does not know the for workstation 1 it is possible for MAC address for Workstation 2. workstation 2 to send a direct pack of data. ICT IGCSE Theory – Revision Presentation 4.1 Networks Compare and contrast the use of a Router and a Switch? Exam Question  ICT IGCSE Common Theory Network – Revision Devices Presentation Modems Analogue > Digital analogue for transmission over telephone lines. Network Interface Card Network Interface Card (NIC) allows you to connect a device to the network. The NIC will contain the MAC address which will be used to identify the computer to the network. Bridges A bridge is used to connect two parts of a LAN network together so they function as a single LAN. Two Switches can be connected using a the Bridge Device. Switch Bridge Switch Understand the use of WiFi and Bluetooth in networks Limited area of network Strength of signal is weaker Possible slow data transfer speeds Easier to hack into/less secure Physical obstacles can interfere with signal/can cause disconnection WiFi is a wireless networking technology makes it possible to connect devices with a wireless connection to a network or to a single computer. Reduced cost of cabling/Safer – won’t trip over wires Easier to connect other devices to the network Makes the computer portable as long as it’s within range of the wireless access point Very slow data transfer speeds Short distance of coverage/limited signal strength Greater risk of interception of data/less secure Supports a limited number of devices in a network Bluetooth is a wireless networking technology designed for very short-range connections. Connecting wireless devices such as mouse, phone, headset to a computer which are close in proximity. Transferring files between devices. Printing Wirelessly from a Tablet or Mobile Phone.  ICT IGCSE Theory – Revision Presentation Bluetooth and WiFi can connect devices together. Discuss the advantages and disadvantages of using Bluetooth or WiFi. Exam Question Bluetooth is more useful when transferring data between two devices whereas WiFi is more suited to full scale networks. The devices connected via Bluetooth should be near to each other whereas WiFi has a larger range. Less data tends to be transferred with Bluetooth. Bluetooth uses a lower bandwidth which means data transfer speeds are slower compare to WiFI. WiFi has better security than Bluetooth however the cost of Bluetooth is cheaper than WiFi. Bluetooth and Wifi both use wireless technology which means there is no need for cables. This reduces costs and trip hazards. Bluetooth is more energy efficient than wifi  ICT IGCSE Methods Theory which can–be Revision used toPresentation connect computers to networks. WiFi: Using WIFI can allow you to connect to the internet from any room in a house without the use of cables. In addition multiple devices can be connected at the same time. Satellite: Satellite can be used almost anywhere in the world. Since it connects via satellites it has better coverage. Its general use is for the internet. 3G / 4G: 3G and 4G are used in smartphones to connect wirelessly to Internet. Allows for access on the move even within areas with no WiFi. 3G and 4G is not affected by rain or snow as it as a form of satellite communication.  ICT IGCSE Theory – Revision Presentation Many computer networks are connected using cables for some are now connected using wireless technology. Discuss the advantages and disadvantages of using wireless networks compared to using cabled networks. Exam Question The advantage of using wireless networks is that it can increase the range of the network making it easier to add additional devices and computers. With a cabled network you would be restricted to the amount of networks ports. Furthermore it could potentially be a cheaper alternative as you would not have to buy cables and modify the building. In contrast the wireless signal could be limited and therefore weaker in some parts of the network due to physical obstacles. The cabled network would provide a more stable and quicker connection. LABEL IT  Cambridge ICT IGCSE Unit 4 - Computer Networks | 275 plays | Quizizz 4. Computer Networks | IGCSE ICT The bus network - Types of network - GCSE ICT Revision - WJEC - BBC Bitesize 1 - Network Architecture - Network+ Study Guide