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NETWORKS

NETWORKS. LANs & WANs Requirements and Advantages & Disadvantages of the Internet. Learning Objectives. Discuss the hardware and software requirements for LANs and WANs to function. Identify the advantages and disadvantages of using the Internet. ROM. COMMUNICATIONS. MAIN MEMORY.

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NETWORKS

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  1. NETWORKS LANs & WANs Requirements and Advantages & Disadvantages of the Internet

  2. Learning Objectives • Discuss the hardware and software requirements for LANs and WANs to function. • Identify the advantages and disadvantages of using the Internet.

  3. ROM COMMUNICATIONS MAIN MEMORY INPUTDEVICES PROCESSOR OUTPUTDEVICES AUXILIARY STORAGE Structure Diagram

  4. Communications • Sending and receiving data to and from other computers.

  5. Communications software • Necessary to allow computers to communicate.

  6. Network Components for a LAN

  7. Network Cards & Cables • Network Interface Cards (NICs) • Allows communication between computers in a LAN. • Cable • Connects the computers together.

  8. LAN 1 Repeater LAN 2 Repeater • Amplifies the signals between two LANs that are too far apart. • Is not intelligent and simply amplifies all signals whether they are intended for computers on the other segment or not.

  9. Hubs Hub

  10. Hubs • Is not intelligent as all signals received by a hub are retransmitted down every other cable connected to it enabling a physical star network. • Multi-port repeaters.

  11. LAN 1 Bridge LAN 2 Bridges • Amplifies the signals between two LANs that are too far apart. • Is intelligent as it only amplifies signals which are intended for computers on another LAN. • Intelligent Repeater

  12. Note: Networks with combined typologies (like the one below) are called Tree or Hybrid networks. Stations Stations Server Server Switch Switch Switch Switch Stations Stations Server Server Backbone

  13. Switch • A switch is intelligent as signals received by a switch are only sent to the intended recipient computer (not down all cables). • Intelligent hub • Like a bridge but can link many LANs. • It allows many terminals all to use the same communications line (backbone – fast medium e.g. optical fibre) between network segments at different times. • If all stations want to access the main network, the switch has no affect on the speed of this link and it may be necessary to upgrade the link to the main network.

  14. WANs (Wide Area Networks) • Networks with computers that cover a large geographical area. • e.g. large companies with offices or factories in widely separated areas, like Microsoft, IBM, Ford, AT&T, etc. • The internet is also an example of a WAN. • Will usually use some form of long range telecommunication e.g. telephone wires, satellite links etc…

  15. Network Components for a WAN

  16. Public network Router Router LAN LAN Routers

  17. Routers • Connect LANs & WANs together. • e.g. connect a LAN to the internet using one IP address. • Directs signals down different routes according to their desired destinations.

  18. Analogue Data • Analogue devices such as: • Clocks • Thermometers • Phones • Speakers • Represent variables by an analogous quantity or variations (modulations) : • Time is represented by the angle of the hands. • Temperature is represented by the height of a column. • Sound waves on a normal phone line or from speakers.

  19. Digital Data • Computers work with data in a digital form. • Streams of 0's and 1's

  20. Need for conversion • If computers are to receive or send analogue data (sensors, speakers, phone lines, etc…). • There must be conversion between analogue and the digital data computers use. • Devices which do this are called: • ADCs (Analogue to Digital Converters)

  21. Modem • Modem: • A hardware device that allows computers or other digital devices e.g. faxes to communicate using telephone lines. • Converts analogue phone signals to digital data which the computer can understand. • Converts digital data to analogue phone signals so they can be transmitted through the phone line

  22. Firewalls & Proxy servers • Firewall • Software to protect LAN from unwanted access. • Proxy server to allow one Internet connection for whole network. • This allows more control over the internet access of the workstations on the LAN as it acts as an intermediary server.

  23. Internet • The Internet is worldwide and intended to be accessed by anybody. • A global network connecting millions of computers. • More than 100 countries are linked into exchanges of data, news and opinions.

  24. Advantages • Convenience: • accessible at home, work, or through a wireless device • Easy to contact other people no matter where they are. • Access to other cultures • Access to a vast amount of information • Can be used Night or Day - it never stops • Can be used to learn (or teach) • Makes it possible to Telework • Possible to buy and sell things online

  25. Advantages • Can present their work more neatly • Pupils can share ideas • Less waste of paper

  26. Disadvantages • Must have a home computer • Transmission of viruses • Must have Internet / Modem • Must remember passwords / usernames • Pupils can copy off others

  27. Disadvantages • Undesirable sites may be accessed • Have to pay for internet access • May receive unsolicited e-mails from undesirable characters • Health reasons • Demand on equipment • Can waste time exploring unreliable sites • Can get distracted playing games

  28. Plenary • What are the hardware and software requirements for LANs and WANs? • LANs & WANS • Communications Software • Cable • Server • Network Card • WANs • Communications Software • Server • Modem

  29. Plenary • What are the advantages and disadvantages of using the Internet?

  30. Advantages • Allows communication. • Pupils can share ideas. • Large amounts of educational material. • Allows students to access information to help with studies and to enjoy their learning. • Allows student to learn at own speed / at own times.

  31. Disadvantages • Many sites do not give accurate information. • Many sites give access to inappropriate material (downloading music / ordering drugs / watching pornography). • Health and Safety problems. • Sites available to buy coursework / helps to cheat in examinations. • May allow hacker into your system / viruses prevalent.

  32. Disadvantages • Undesirable sites may be accessed • Have to pay for internet access • May receive unsolicited e-mails from undesirable characters • Health reasons • Demand on equipment • Can waste time exploring unreliable sites • Can get distracted playing games

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