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Wireless network

Wireless network. Usually use Radio Frequency (RF) technology transmit and receive data over the air Adv : providing all the features of wired LAN without the limitations of a cable Disadv : lower transmission speed higher cost (when c.f. wired network). Wireless LAN

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Wireless network

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  1. Wireless network • Usually use Radio Frequency (RF) technology • transmit and receive data over the air • Adv : • providing all the features of wired LAN • without the limitations of a cable • Disadv : • lower transmission speed • higher cost (when c.f. wired network)

  2. Wireless LAN • usually used in complement with a wired LAN • becoming an alternative for wired LAN • by means of an access point (AP) • a device that transports data between a wireless LAN and a wired LAN • with wireless LAN Card • wireless network interface card • wireless node • with area of coverage

  3. One of the advantage of Wireless LAN • provide mobility • suitable for • school campus • taking inventory in a warehouse • making order for a restaurant • hospitals • construction site • temporarily office • health care ; retail ; manufacturing ; warehousing ; education

  4. Network Topology • Network Topology = logical layout or the way in which the computers and other network devices are connected • Each computer / device = node • Common Topologies • Bus topology • Star topology • Ring topology

  5. Bus Topology • all computers and other network devices are connect to a single central cable

  6. Adv : • Easy to set up • failure of one device does not affect the rest of the bus network • Disadv : • failure of any point on the central bus may lead to the failure of the whole network • only one PC can send data on a bus network • therefore number of computer attached to the bus will affect the performance of network • more PC, more waiting, slower the network

  7. 3 concepts about Bus Topology • sending the signal • signal bounce (CSMA / CD) • terminator

  8. Sending the signal • in form of electronic signals • sent to all computers on the network • only the computer whose address matches the address encoded in the original signal accepts the information • all other PC reject the data

  9. Signal Bounce • as data is sent to the entire network • travels from one end of the cable to the other • if signal is allowed to continue uninterrupted • signal will keep bouncing back and forth • other PC cannot send signals • therefore signal must be stopped after it has a chance to reach the proper destination address

  10. Terminator • to stop the signal from bouncing • a component called a terminator • placed at each end of the cable • to absorb free signals • to clear the cable so that other PCs can send data • both end should plug with terminator

  11. Star Topology • all the devices on the network • connect to a central device (hub / switch / router) • thus forming a star • if one device / computer fail • not affecting the others. • If the connecting cable between an device and the central device fail / has problem • not affecting the others

  12. If the central device fails • power / networking problem • the entire network is not working • Star topology is the most common type of network topology

  13. Advantage : • centralized resources • centralized management • Disadvantage : • great deal of cable in a large network installation • if central point fail, the entire network goes down

  14. One PC fail • if one PC, or one of the cable that connects it to the hub fails (on a star network) • only the failed computer will not be able the • send, or • receive network data • no bouncing and terminator

  15. Ring Topology • all the devices are connected on a circular path • data flows in only one direction • For sending data • data travels to each computer on the ring until it reaches its destination • control data transmission by using • token-passing scheme

  16. Token • control signal passes from one device to the next • indicating which device is allow (has the right) to transmit signal • thus ensure the only one computer at a time can transmit data • therefore, no data collision • Disadv : • if a device on a ring network fail / cable fail • whole network fail

  17. Topologies : • usually more than 1 topology is used in a network • For example : school network • bus + star

  18. Network Operating System • Desktop Operating System • e.g. Windows 98 / ME • good to use • with necessary software for establishing communication with a network server • But if want to • manage network resources • control the flow of data • maintain security …………….. !!!!!!!!

  19. Thus need a Network Operating System (NOS) • NOS : • has 2 components : • Network Server Software • Network Client Software

  20. Network Server Software • e.g. Mac OS X Server / Windows .NET Server • control file access from the server’s hard disk • manage print queue • tracks user data such as user Ids and passwords • Network Client Software • Mac OS X, Windows XP Professional • gather login information • handles drive mapping • directs printouts to the network printers

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