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Networks

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  • 1. Network Hardwareand Software
  • 2. What is a network? A network consists of two or more computers that are linked in order to:  share resources (such as printers and CD-ROMs),  exchange files, or  allow electronic communications
  • 3. How are they linked? Computers on a network may be linked through:  cables,  telephone lines,  radio waves, satellites or  wireless technologies
  • 4. The two basic types of networks include:Local Area Networks LAN(LAN)Wide Area Networks(WAN) WAN
  • 5. Local area networksLANs are confined to a relatively smallarea such as a school or a buildingLANs usually have one computerdesignated as the file serverOther computers are connected to thenetwork by cables connecting networkinterface cards in each computer
  • 6. Wide Area Networks WANs connect larger areas, such as whole states, or even the world. Transoceanic cables and satellites are used to connect WANs
  • 7. ProtocolA protocol is a set of PROTOCOL =rules that governs the SET OF RULES ABOUTcommunications COMMUNICATIONbetween computers S BETWEEN NETWORKS!on a networkThese rules includeguidelines thatregulate the method ofaccess, types ofcabling and speed ofdata transfer
  • 8. The most common protocols are: Ethernet Local Talk Protocol = a formal Token Ring description of a set of rules and conventions FDDI that govern how ATM devices on a network exchange informationDid you ever wonder what HTTP in web addresses wasabout? It stands for HyperText Transfer Protocol
  • 9. Ethernet Most widely used Uses an access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection
  • 10. What does that mean?Each computer in thenetwork ‘listens’ to the A bit like waiting forcable before sending your younger sister toanything through the get off the telephonenetwork. If the network perhaps?is clear, the computerwill transmit.If another computer isalready transmitting onthe cable, the computerwill wait and try againwhen the line is clear
  • 11. Ethernet (continued)Sometimes, two computersattempt to transmit at thesame instant. When thishappens, a collision occurs.Each computer then backs offand waits a random amount oftime before attempting toretransmit.It is normal to havecollisions using this method, CSMA/CD =Carrierbut the delays caused by Sense Multiplecollisions and transmissions is Access /Collisionsmall, and does not effect Detectionspeed of transmission on thenetwork
  • 12. Ethernet (continued)Ethernet protocolallows for data to betransmitted overtwisted pair, coaxialor fiber optic cableat a speed of 10Mbps(more on that later)
  • 13. Fast EthernetTo allow for fastertransmission, theEthernet protocol hasdeveloped a newstandard thatsupports 100 MbpsFast Ethernetrequires the use ofmore expensiveequipment andnetwork cards
  • 14. Gigabit EthernetThe Ethernetprotocol has alsodeveloped a new One gigabit perstandard that allows second = onetransmission of 1 thousandGbps (gigabit per megabits persecond) second
  • 15. Local TalkLocal Talk is a networkprotocol that wasdeveloped by Apple forMacintosh computersLocal Talk uses theCSMA/CA method(Carrier Sense MultipleAccess with CollisionAvoidance) which works ina similar way toCSMA/CDIt is a lot slower thanEthernet (only 230 Kbps)
  • 16. Token RingToken ringprotocol involves‘token-passing’.It is not as A single electronic ‘token’popular as moves around the ring from one computer to the next. If aEthernet protocol computer wishes to transit and receives an empty token, it attaches data to the token which then proceeds around the ring until it comes to the computer the data is meant for.
  • 17. FDDIStands for FiberDistributed DataInterfaceIs used mainly toconnect two or moreLANs, often overlarge distancesCan operate overfiber optic cable at100 Mbps
  • 18. ATMStands for AsynchronousTransfer ModeTransmit data at a speedof 155 Mbps and higherWorks by transmitting alldata in small packets offixed size (other protocolstransfer variable sizepackets)Like FDDI , is most oftenused to connect two ormore LANs
  • 19. Where does TCP/IP fit into all this???TCP/IP is the protocol that is used for thetransmission of information over the InternetIP (Internet Protocol) - the main delivery systemfor information over the InternetTCP (Transport Control Protocol) - used tobreak apart and rebuild information that travelsover the Internet
  • 20. Network HardwareNetwork hardwareincludes: Computers Peripherals Interface cards and Other equipment needed to perform data processing and communications within the network
  • 21. File serversA very fast computerwith a large amountof RAM and storagespace along with afast networkinterface cardThe networkoperating systemsoftware resides onthis computer
  • 22. WorkstationsAll computersconnected to the fileserver on a networkare calledworkstations
  • 23. Network interface cardsThe network interface card(NIC) provides the physicalconnection between thenetwork and the computerworkstation.Most NICs are internal withthe card fitting into anexpansion slot in thecomputer.Three common networkinterface connections areEthernet cards, Local Talkconnectors and TokenRing cards
  • 24. Ethernet cardsThe most commonNetwork Interface Co-axialCards are Ethernet cablecardsThey containconnections foreither coaxial ortwisted pair cables, Twisted pair cableor both
  • 25. Concentrators / Hubs A concentrator is a device that provides a central connection point for cables from workstations, servers and peripherals Hubs are multi-slot concentrators
  • 26. SwitchesWhile hubs provide an easyway to scale up andshorten the distance thatthe packets must travel toget from one node toanother, they do not breakup the actual network intodiscrete segments. That iswhere switches come in.
  • 27. Switches (continued)A vital difference between a hub and a switch is that allthe nodes connected to a hub share the bandwidthamong themselves, while a device connected to a switchport has the full bandwidth all to itself.Think of a switch as a ‘clever’ hub
  • 28. RepeatersA signal loses strength as it passesalong a cable, so it is often necessaryto boost the signal with a device calleda repeaterA repeater might be a separate device,or might be part of a concentrator
  • 29. BridgesA bridge is a device that allows youto segment a large network into twosmaller, more efficient networks
  • 30. RoutersA router translatesinformation from onenetwork to anotherThe router directs traffic toprevent “head-on”collisionsIf you have a LAN that youwant to connect to theInternet, you will need arouter to serve as thetranslator betweeninformation on your LANand the Internet
  • 31. Routers (continued)
  • 32. CablingNetwork cabling is themedium through whichinformation usuallymoves from onenetwork device toanotherThere are severaldifferent types of cablecommonly used inLANSSome networks use avariety of cable typeswithin the one network
  • 33. Unshielded Twisted Pair (UTP) CableTwisted pair cablescome in two varieties:shielded andunshielded.Unshielded (UTP) isthe most popularShielded twisted pair isused only inenvironments wherethere may be electricalinterference
  • 34. UTP (continued)UTP has four pairs of wires inside the jacketEach pair is twisted with a different number oftwists per inch to help eliminate interferencefrom adjacent pairs
  • 35. UTP ConnectorThe standardconnector for UTPcabling is an RJ-45.It looks like atelephone styleconnection
  • 36. Coaxial cableCoaxial cable has a single copper conductor at itscentre with a plastic layer between the centreconductor and the braided metal shieldAlthough coaxial cabling is difficult to install, it ishighly resistant to signal interference
  • 37. Coaxial cable connectors The most common type of connector used with coaxial cables is the BNC connector
  • 38. Fiber Optic CableFiber optic cabling consists of a center glasscore surrounded by several layers of protectivematerialsIt transmits light rather than electronic signalsIt is the standard for connecting networksbetween buildings, due to its immunity to theeffects of moisture and light
  • 39. Fiber Optic (continued)Fiber optic cable has the ability to transmitsignals over much longer distances thancoaxial or twisted pairIt can also carry information at vastly greaterspeedsFiber optic cable is more difficult to install thanother cabling
  • 40. Wireless LANSWireless networks use high frequency radiosignals to communicate between theworkstations and the fileserver or hubs.Disadvantages of wireless networks are: they are expensive (relatively), provide poor security, are susceptible to interference and are slower than cabled networks
  • 41. Network Operating SoftwareNetwork operatingsystems co-ordinate theactivities of multiplecomputers across anetworkThe two major types ofnetwork OS are: Peer-to-peer Client/server
  • 42. Peer to peer network OSIn peer to peer network OS,there is no file server or centralmanagement source; allcomputers are considered equalPeer to peer networks aredesign primarily for small tomedium LANSAppleShare and Windows forWorkgroups are examples ofprograms that can function aspeer to peer
  • 43. Client/Server network OSClient/server network OScentralise functions andapplications in one or morededicated file servers.The file server providesaccess to resources andprovides securityNovelle Netware andWindows NT Server areexamples of client/servernetwork operating systems
  • 44. TopologyThe physical topology of a network refers tothe configuration of cables, computers andother peripherals.The main types of network topologies are: Linear Bus Star Ring Tree or Hybrid
  • 45. Linear BusA linear bus topology consists of a main run ofcable with a terminator at each end. All serversworkstations and peripherals are connected tothe linear cable
  • 46. StarA star network isdesigned with eachnode (file server,workstation,peripheral)connected directly toa central networkhub or server
  • 47. RingA ring network isone where allworkstations andother devices areconnected in acontinuous loop.There is no centralserver
  • 48. Tree or hybridA tree or hybridtopology combinescharacteristics oflinear bus and starand/or ringtopologies.It consists of groupsof star-configuredworkstationsconnected to alinear bus backbonecable