Chapter 4


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Chapter 4

  1. 1. Computer Network<br />Chapter 4<br />
  2. 2. “I think there is a world of market for maybe five computers”<br />Thomas J. Watson<br /> Chairman IBM, 1943<br />
  3. 3. Why Use Networks?<br />Network<br />Group of computers and devices<br />Connected by transmission media<br />Stand-alone computer<br />Not connected to other computers<br />Uses local software and data<br />Advantages of networks over standalone computers<br />Device sharing by multiple users<br />Saves money and time<br />Central network management<br />
  4. 4. Types of Networks<br />Network models<br />Peer-to-Peer<br />Client/server<br />
  5. 5. Peer-to-Peer Network<br />Figure 1-1 Resource sharing on a simple peer-to-peer network<br />
  6. 6. Client/Server Networks<br />Figure 1-2 Resource sharing on a client/server network<br />
  7. 7. Computers<br />Printer<br />Copier<br />Fax<br />Scanner<br />Personal Digital Assistants<br />Cell Phones<br />Radios<br />RFID (Radio Frequency ID)<br />Networks are everywhere<br />
  8. 8. Introduction<br /><ul><li>Today people are often linked by wires or air (wireless) carrying voice and computer signals via the telephone system.
  9. 9. Data communications dominate the world.
  10. 10. Computer Network: The linkage of computer systems by means of communication lines or channels (e.g., fiber optic, microwave, satellite, telephone line, 802.11)</li></li></ul><li>Computer Network<br />At least two computers need to be connected<br /><ul><li>Copper
  11. 11. Fiber Optics
  12. 12. Microwaves
  13. 13. Infrared
  14. 14. Satellites</li></li></ul><li>Data Communications<br />Data Processing<br />+<br />Telecommunications<br />= Data Communications<br />
  15. 15. Data Communication<br />Electronic transfer of information from one computer to another.<br />Data<br />Text<br />Pictures<br />Graphics<br />Video<br />Voice<br />
  16. 16. Network Components (Examples)<br /> Introduction<br />1-12<br />Links<br />Interfaces<br />Switches/routers<br />Ethernet card<br />Large router<br />Fibers<br />Wireless card<br />Coaxial Cable<br />Switch<br />
  17. 17. Why network?<br /><ul><li>Resource sharing
  18. 18. Files, Applications, Printer, Fax
  19. 19. Communication Medium
  20. 20. Email, Collaboration, videoconferencing
  21. 21. E-business
  22. 22. Supply-chain, inventory, B2C</li></li></ul><li>Business Applications of Networks<br />A network with two clients and one server.<br />
  23. 23. Business Applications of Networks (2)<br />The client-server model involves requests and replies.<br />
  24. 24. Home Network Applications<br /><ul><li>Access to remote information
  25. 25. Person-to-person communication
  26. 26. Interactive entertainment
  27. 27. Electronic commerce</li></li></ul><li>Communication Lines/Channels<br />Fiber optic<br />Microwave<br />Satellite<br />Telephone Line etc.<br />
  28. 28. Impact of Data Communications<br />It enables information to be accessed and transmitted quickly.<br /><ul><li>Automatic Data Collection or Polling (i.e. Chuck E. Cheese) –menu update, get info from POS</li></ul>It allows the storing of information in a centralized database that may be shared by a few users in a small computer network or by thousands of users in a large computer network.<br />It facilitates centralized management and decentralized operations (e.g., restaurant chain).<br />
  29. 29. Impact of Data Communications<br />It links business processes performed by independent computer systems to improve organizational efficiency and effectiveness<br />It links a business to its customers<br />Communication devices, such as cell phones, personal digital assistants, etc.<br />
  30. 30. Local Area Network<br />LAN is linkage of computers in a specific geographical area (usually within an office or building) such as in hotels, restaurants, or country clubs using transmission medium such as twisted pair wire or coaxial cable.<br />
  31. 31. Why Local Area Network (LAN)?<br />Increased processing and transfer requirements in many graphics-intensive applications now require significantly higher transfer rates (data, audio, image, video)<br />Decreased cost of storage space leads to program and file bloat, increased need for transfer capacity<br />Watch this video<br />
  32. 32. Basic LAN Hardware<br />Computers/Server(s)<br />Resources<br />Cables<br />Connectors (Hubs)<br />Network Interface Cards (Ethernet)<br /> ADVANCED<br />Bridges<br />Routers<br />
  33. 33.
  34. 34. Full versus half duplex<br />Half duplex: communication can happen in both directions but one at a time (like walkie-talkie)<br />Full duplex: communication can happen in both directions at the same time (like a phone)<br />
  35. 35. Client<br />Is any network entity that can request resources from the network. <br />Workstations can be clients but not all clients are workstations<br />For example, a printer can request resources from the network, it is a client, not a workstation. <br />
  36. 36. Server<br />A computer that provides resources to the clients on the network.<br />Servers are typically powerful computers<br />
  37. 37. Switch<br />
  38. 38. Hub vs. Switch<br />Hub—sends signals to all computers connected<br />Switch– sends signals to intended computer(s)<br />
  39. 39. LANs share<br />Files (databases)<br />Resources (Printers, fax)<br />Programs (Fidelio, MS Office)<br />Working together<br />Communication<br />
  40. 40. WAN (Wide Area Network ) Communications Hardware<br />WAN=Connection of at least two LANs<br />Down-line processor/ Multiplexer<br />Front-end Processor<br />PBX(Private Branch Exchange)<br />Watch Video<br />
  41. 41. WAN Connection Types<br /><ul><li>Private Lines
  42. 42. Frame Relay
  43. 43. Dial-Up
  44. 44. Satellite
  45. 45. Down Line Processor or Multiplexer
  46. 46. Front-end Processor
  47. 47. PBX Switchboard
  48. 48. Shared Lines
  49. 49. DSL
  50. 50. Cable</li></li></ul><li>WAN in Hospitality<br />Global Reservation System<br />Central Reservation System<br />Property Management System<br />
  51. 51. LA<br />Miami<br />NYC<br />Boston<br />
  52. 52. Hotel Marriott Miami<br />Hotel Marriott NYC<br /><ul><li> Dial-up (max 56Kbps)
  53. 53. ISDN (128Kbps)
  54. 54. DSL (1.5Mbps)
  55. 55. Cable (3.5Mbps)</li></ul>Shared Connection<br />
  56. 56. Hotel Marriott Miami<br />Hotel Marriott NYC<br /><ul><li>T-1 (1.5Mbps)
  57. 57. Frame Relay (1.5Mbps)
  58. 58. T-3 (43Mbps)
  59. 59. OC3 (155Mbps)
  60. 60. ATM (622Mbps)</li></ul>Dedicated Connection<br />
  61. 61. Hotel Marriott NYC<br /><ul><li>802.11b (11Mbps)
  62. 62. 802.11g (54Mbps)
  63. 63. 802.11a (54Mbps)
  64. 64. 802.11n (<100Mbps)</li></ul>WLAN -Dedicated / Shared Connection<br />
  65. 65. A Small LAN<br />
  66. 66. Wireless LAN<br /><ul><li>Advantages</li></ul>Wireless LANs are simple to set up. It literally can take 10 minutes for a simple wireless network to be setup.<br />Wireless LANs are cheap to create.<br />When it is not possible to wire, Wireless LANs come into rescue.<br /><ul><li>Disadvantages</li></ul>Security is the biggest down side of wireless LANs.<br />
  67. 67.
  68. 68. HP Server<br />IBM Server<br />
  69. 69. Network Hardware: Repeaters<br />Extend the length of transmission media<br />
  70. 70. Server Types<br />File Server: holds and distributes files<br />Print Server: handles printing jobs from clients<br />Proxy Server: performs a function on behalf of other computers<br />Application Server: hosts a network application (i.e. Marriott’s central reservation system, Marsha)<br />Web Server: handles web pages and other web content (i.e.,,<br />Mail Server: hosts and delivers electronic mail.<br />Fax Server: sends and receives faxes electronically.<br />Voice over IP Server: Handles calls on Internet Protocol<br />
  71. 71. Physical Media<br />Coaxial Cable<br />Thinnet (BNC Connector and RG-58)<br />Twisted Pair Cable<br />Category 1 – Category 6<br />RJ-11 and RJ-45 Connectors<br />Fiber Optic Cable<br />
  72. 72. Coaxial Cable<br />Contains a center conductor, made of copper, surrounded by a plastic jacket<br />Teflon type covering  plenum-rated coating does not burn easily<br />Coax is not used in LANs today but still used widely by TV cable operators<br />
  73. 73. Thin Ethernet<br />Thinnet<br />10Base-2<br />Thin coaxial cable– smaller than thick coaxial cable<br />
  74. 74. A Stripped-back Thinnet<br />
  75. 75. Thinnet<br />
  76. 76. Connectors<br />With thinnet, you use BNC (BayoNet Connector) connectors to attach stations to the network. <br />BNC Connector locks securely with a quarter-twist motion<br />A T-connector is used to connect backbone devices<br />
  77. 77. Male and Female BNC Connectors<br />
  78. 78.
  79. 79. F type connector<br />Popular with TV Cable and Cable Modems<br />
  80. 80. Twisted-pair cable<br />Consists of multiple, individually insulated wires that are twisted together in pairs<br />Sometimes a metallic shield is placed around pairs shielded twisted pair (STP)<br />Unshielded twisted pair (UTP)<br />
  81. 81. Why twisted?<br />Electromagnetic signals create interference  crosstalk<br />Twisting the cables in pairs reduce intereference<br />Most common cable<br />
  82. 82. Twisted-pair<br />Cheaper<br />Easy to work with<br />Transmission rates are good<br />
  83. 83. Fiber Optic Cable<br />A glass or plastic fiber that carries light along its length. This cable is the fastest and most expensive transmission medium in the world today<br />
  84. 84. Advantages of Fiber Optic Cable<br /><ul><li>Superior System Performance
  85. 85. Greatly increased bandwidth and capacity
  86. 86. Lower signal loss
  87. 87. Immunity to Electrical Noise
  88. 88. Immune to noise (electromagnetic interference [EMI] and radio-frequency interference [RFI]
  89. 89. Lower bit error rates
  90. 90. Signal Security
  91. 91. Difficult to tap
  92. 92. Light weight</li></li></ul><li>Topology<br />Arrangement of workstations in a shared medium environment<br />Logical arrangement (data flow)<br />Physical arrangement (cabling scheme)<br />
  93. 93. Network Topologies<br />The manner in which workstations are connected together physically and logically is referred to as a NETWORK TOPOLOGY.<br />4 Types: <br />Bus (Video)<br />Ring (Video)<br />Star (Video)<br />Hybrid<br />
  94. 94.
  95. 95. BUS Topology<br />Information transfer<br />Terminators<br />Setup is simple<br />Expansion<br />Repair<br />Cost<br />
  96. 96.
  97. 97. STAR Topology<br />Central network connector (switch)<br />Less than 100m.<br />Expansion—switch-uplink<br />Troubleshooting<br />Cost—cable<br />
  98. 98.
  99. 99. Ring Topology<br />Information flows one way<br />Close together<br />Expansion<br />Troubleshooting<br />Cost<br />
  100. 100.
  101. 101. Hybrid Topology<br />
  102. 102. Why Hybrid (Tiered)?<br />Reliability—less service interruption<br />Capacity- not easily saturated<br />Cost – low cost networks can build up<br />Needs- not every department need the same equipment (accounting vs. graphics)<br />
  103. 103.
  104. 104. Network Management<br /><ul><li>Network management is a systematic approach to planning, organizing, and controlling networks.
  105. 105. The five basic functions of network management are:</li></ul>Fault management<br />Configuration management<br />Performance management<br />Security Management<br />Accounting Management<br />
  106. 106. Chapter 4<br />The End<br />