L6_ Computer Networks.pdf

UNIT 2: Computer NETWORKS Types of networks; ❏ local area network (LAN) ❏ wireless local area network(WLAN) ❏ wide area network (WAN). - Difference between LANs and WANs, their main characteristics; - intranets and the Internet - discuss the problems of confidentiality and security of data, includ...

UNIT 2: Computer NETWORKS Types of networks; ❏ local area network (LAN) ❏ wireless local area network(WLAN) ❏ wide area network (WAN). - Difference between LANs and WANs, their main characteristics; - intranets and the Internet - discuss the problems of confidentiality and security of data, including problems surrounding common network environments; - identify the need for encryption, authentication techniques, including the use of user identification and passwords, when using common network environments such as the Internet. Setting up a Network ISP (Internet Service Provider) Set up an account with an Internet Service Provider (ISP) to receive an internet connection to your location Web Browser: Router: To browse the internet. To connect your LAN to the Internet (WAN) Switch/Hub: Email: To connect Network Devices together using cables. To send email messages including attachments to other users. Network Cables: To create physical connections. Security: Firewall: To keep network secure from external threats. Anti Virus/Spyware software to protect your computer from external threats Servers: (Viruses/Hackers) To manage network functions such as network security, network file storage, share resources etc. Describe what an ISP is and, apart from security measures, describe what it offers its customers. Exam Question Internet Service Provider (ISP) provides Internet access. ISPs often offers web space and domain name to create own website. Also the ISP provides users with an email address. The ISP also provides a router to connect to the internet. In addition they may also offer storage space to save data in the cloud.  T YPES OF N ETWORK - LAN (L OCAL A REA N ETWORK ) A Local Area Network is a network confined to one building or site. Often a LAN is a private network belonging to an organisation or business. Because LANs are geographically small, they usually use cables or low-power radio (wireless) for the connections.  T YPES OF N ETWORK - W IRELESS L OCAL A REA N ETWORK (WLAN) A wireless LAN (WLAN) is a LAN that uses radio signals (WiFi) to connect computers instead of cables. At the centre of the WLAN is a wireless switch or router - a small box with one or two antennas sticking out the back - used for sending and receiving data to the computers. (Most laptops have a wireless antenna built into the case.)  T YPES OF N ETWORK - W IDE A REA N ETWORK (WAN) A Wide Area Network is a network that extends over a large area. A WAN is often created by joining several LANs together, such as when a business that has offices in different countries links the office LANs together. Because WANs are often geographically spread over large areas and links between computers are over long distances, they often use quite exotic connections technologies: optical fibre (glass) cables, satellite radio links, microwave radio links, etc.  B LUETOOTH (P ERSONAL A REA N ETWORK ) Bluetooth is a wireless networking technology designed for very short-range connections (typically just a few metres). The idea of Bluetooth is to get rid of the need for all of those cables (e.g. USB cables) that connect our computer to peripheral devices such as printers, mice, keyboards, etc. Bluetooth devices contain small, low-power radio transmitters and receivers. When devices are in range of other Bluetooth devices, they detect each other and can be 'paired' (connected)  ICT IGCSE Theory – Revision Presentation 4.1 Networks Describe the differences between the common network environments (LAN, WAN, WLAN)? Exam Question LAN (Local Area Network) WAN (Wide Area Network) WLAN (Wireless Local Area Network) ∙ Smaller geographical area ∙ Larger geographical area ∙ Uses wireless signals to connect devices ∙ Confined to one building ∙ LANs connected together form ∙ Access Points are connected to the a WAN wired networks. Local Area Networks (LANs) normally cover a smaller geographical area confined normally to one building. Wide Area Networks are LANs which have been connected together with a router. They normally cover a larger geographic area. The connection between the LANs could either be with cables or satellite signals. Wireless Local Area Networks use wireless signals to connect devices. Access Points are connected to the wired networks. LAN T OPOLOGIES ( ARRANGEMENT ) BUS network, a long, central cable, the ‘bus’ is used to connect all of the computers together. Each computer has a short cable linking it to the ‘bus’. Is cheap to install (just one long cable) Can be quite slow since all computers share the same cable when communicating Will stop working if there is a break in the central bus cable. LAN T OPOLOGIES ( ARRANGEMENT ) Ring Network - each computer is connected to a loop of cable, the ‘ring’. (If you took a bus network and connected the ends of the bus cable together, you would have a ring network.) A ring network… Can cope with a break in the ring cable since all computers are still joined together (it is now a bus network) LAN T OPOLOGIES ( ARRANGEMENT ) Star Network - every computer is connected to a central device. The device passes messages between computers. At the centre of a star network you might use a hub (cheap, but slower) or a switch (more expensive, but faster). Is quite expensive to install (you have to buy lots of cable and the central device) Is very fast since each computer has its own cable which it doesn’t need to share Can cope with a broken cable (only one computer will be affected) Will stop working if the central device breaks Is the most common network topology LAN T OPOLOGIES ( ARRANGEMENT ) Hybrid Network A hybrid network is simply one that combines two or more of the above basic topologies. E.g. A network that has several star networks linked together is a hybrid network  N ETWORKING H ARDWARE Any computer that is to be connected to a network, needs to have a network interface card (NIC). Network Cable - To connect together different devices to make up a network, you need cables. A hub - device that connects a number of computers A together hub is a ‘dumb’ device: to make if it receives a message, it sends a it toLAN. every computer on the network. This means that hub-based networks are not very secure - everyone can listen in to communications.  N ETWORKING H ARDWARE A switch, like a hub, is a device that connects a number of computers together to make a LAN. It is a more ‘intelligent’ device than a hub: if it receives a message, it checks who it is addressed to, and only sends it to that specific computer. A router is a network device that connects together two or more networks. (common use of a router is to join a home or business network (LAN) to the Internet (WAN).  N ETWORKING H ARDWARE proxy server is a computer setup to share a resource, usually an Internet connection. (often used instead of router since additional software can be easily installed on the computer such as anti-virus, web filtering etc.) A bridge is a network device that typically links together two different parts of a LAN.  F IREWALL A firewall is a device, or a piece of software that is placed between your computer and the rest of the network (where the hackers are!) If you wish to protect your whole LAN from hackers out on the Internet, you would place a firewall between the LAN and the Internet connection. A firewall blocks unauthorised connections being made to your computer or LAN. Normal data is allowed through the firewall (e.g. e-mails or web pages) but all other data is blocked.  M ODEM Before the days of broadband Internet connections, most computers connected to the Internet via telephone lines (dial-up connections). The problem with using telephone lines is that they are designed to carry voices, which are analogue signals. They are not designed for digital data. The solution was to use a special device to join the digital computer to the analogue telephone line. This device is known as a modem. A modem contains a DAC and an ADC.  ICT IGCSEand Intranets Theory the –Internet Revision Presentation Internet Internet is Public (available to all Typical uses of an internet would be: users) Internet is network of networks Viewing web pages Internet is global Sending and receiving e-mail messages Internet has more information than an Sharing files intranet Communicating using voice (VOIP) and video (video-conferencing) Playing multi-player games Streaming Video/audio Content Online Shopping/Banking Intranet Intranet is within one organisation Typical uses of an intranet would be: (Private) Intranets tend to be Viewing internal web pages (e.g. company policed/managed schools, university's etc.) Intranet has an extra layer of security Internal e-mail and instant- Data found in an intranet is likely to be messaging between workers Sharing of internal documents more reliable/relevant than that found on the Internet  I NTRANET An intranet is the name given to a private network that provides similar services to The Internet: e-mail, messaging, web pages, etc. However, these services are only for the users of the intranet – they are private, not public (unlike Internet services which are generally public). Businesses and other organisations often have intranets for use by their employees.  S ETTING U P A S MALL N ETWORK 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 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 network security, network file storage, shared resources (such as printers) 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  P REVENTING U NAUTHORISED A CCESS Physical Security Use a Username and Have a Good Password Always Install and Use a Firewall Securing Your Data: ○ Data Encryption- process of converting information into a form that is meaningless to anyone except holders of a ‘key’.  ICT IGCSE Theory – Revision Presentation Describe the differences between the internet and intranet? Exam Question Internet is global network of networks. It is open to the public domain whereas the intranet is private and normally within on organisation. The intranet requires authentication to log on which provides an extra layer of security. Information found on the intranet will more reliable and relevant then the internet because the intranet tends to be policed/managed. However more information is available on the internet. Give three reasons why some companies have intranets? It is possible to prevent employees accessing undesirable websites. The company can ensure that available information is specific to their needs. Also it will make it is easier to make sure confidential messages stay within the company. Furthermore there is less chance of company computers being hacked.  ICT IGCSE Theory – Revision Presentation 4.1 Networks In order to make reliable information available to all students, schools often put the information on their intranet. Describe what is meant by an intranet? Exam Question An intranet is a computer network which normally exists usually within one organisation. The intranet meets the internal needs of an organization. Intranet is private and tends to be policed or managed. Intranet has an extra layer of security and data found in an intranet is likely to be more relevant to the users’ needs.  ICT IGCSE Accessing the Theory Internet – Revision Presentation Device Advantages Disadvantages More portable and smaller in size compared Touch pad may be difficult to laptop computers to desktop computers. use to navigate webpages. Bigger screens compared to tablets and phones. Processors are not as fast as desktop computers. Stable internet connection since the Has to be connected to a power Desktop connection is normally wired. supply at all times. Use of input devices including pointing devices Not portable. to make navigation easier. Tablet: More portable than desktops/laptops Signal strength dependant on Tablets however less than phones. location. Smaller display screen. Mobile: Portable: Easy to carry around and use Not all websites designed to be whilst on the move. used by mobiles/tablets. Touch screen may be difficult Smart Phones Mobile: Always likely to have a mobile phone to use. at all times. Limited battery Life. Mobile: Can access internet via phone networks (4G)  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