1. Computer Network Chapter 4

2. “I think there is a world of market for maybe five computers” Thomas J. Watson Chairman IBM, 1943

3. Why Use Networks? Network Group of computers and devices Connected by transmission media Stand-alone computer Not connected to other computers Uses local software and data Advantages of networks over standalone computers Device sharing by multiple users Saves money and time Central network management

4. Types of Networks Network models Peer-to-Peer Client/server

5. Peer-to-Peer Network Figure 1-1 Resource sharing on a simple peer-to-peer network

6. Client/Server Networks Figure 1-2 Resource sharing on a client/server network

7. Computers Printer Copier Fax Scanner Personal Digital Assistants Cell Phones Radios RFID (Radio Frequency ID) Networks are everywhere

9. Data communications dominate the world.

11. Fiber Optics

12. Microwaves

13. Infrared

15. Data Communication Electronic transfer of information from one computer to another. Data Text Pictures Graphics Video Voice

16. Network Components (Examples) Introduction 1-12 Links Interfaces Switches/routers Ethernet card Large router Fibers Wireless card Coaxial Cable Switch

18. Files, Applications, Printer, Fax

19. Communication Medium

20. Email, Collaboration, videoconferencing

21. E-business

23. Business Applications of Networks (2) The client-server model involves requests and replies.

25. Person-to-person communication

26. Interactive entertainment

29. Impact of Data Communications It links business processes performed by independent computer systems to improve organizational efficiency and effectiveness It links a business to its customers Communication devices, such as cell phones, personal digital assistants, etc.

30. Local Area Network 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.

31. Why Local Area Network (LAN)? Increased processing and transfer requirements in many graphics-intensive applications now require significantly higher transfer rates (data, audio, image, video) Decreased cost of storage space leads to program and file bloat, increased need for transfer capacity Watch this video

32. Basic LAN Hardware Computers/Server(s) Resources Cables Connectors (Hubs) Network Interface Cards (Ethernet) ADVANCED Bridges Routers

34. Full versus half duplex Half duplex: communication can happen in both directions but one at a time (like walkie-talkie) Full duplex: communication can happen in both directions at the same time (like a phone)

35. Client Is any network entity that can request resources from the network. Workstations can be clients but not all clients are workstations For example, a printer can request resources from the network, it is a client, not a workstation.

36. Server A computer that provides resources to the clients on the network. Servers are typically powerful computers

37. Switch

38. Hub vs. Switch Hub—sends signals to all computers connected Switch– sends signals to intended computer(s)

39. LANs share Files (databases) Resources (Printers, fax) Programs (Fidelio, MS Office) Working together Communication

40. WAN (Wide Area Network ) Communications Hardware WAN=Connection of at least two LANs Down-line processor/ Multiplexer Front-end Processor PBX(Private Branch Exchange) Watch Video

42. Frame Relay

43. Dial-Up

44. Satellite

45. Down Line Processor or Multiplexer

46. Front-end Processor

47. PBX Switchboard

48. Shared Lines

49. DSL

51. LA Miami NYC Boston

53. ISDN (128Kbps)

54. DSL (1.5Mbps)

55. Cable (3.5Mbps)Shared Connection

57. Frame Relay (1.5Mbps)

58. T-3 (43Mbps)

59. OC3 (155Mbps)

60. ATM (622Mbps)Dedicated Connection

62. 802.11g (54Mbps)

63. 802.11a (54Mbps)

64. 802.11n (<100Mbps)WLAN -Dedicated / Shared Connection

65. A Small LAN

68. HP Server IBM Server

69. Network Hardware: Repeaters Extend the length of transmission media

70. Server Types File Server: holds and distributes files Print Server: handles printing jobs from clients Proxy Server: performs a function on behalf of other computers Application Server: hosts a network application (i.e. Marriott’s central reservation system, Marsha) Web Server: handles web pages and other web content (i.e. Marriott.com, Hilton.com, Starwood.com) Mail Server: hosts and delivers electronic mail. Fax Server: sends and receives faxes electronically. Voice over IP Server: Handles calls on Internet Protocol

71. Physical Media Coaxial Cable Thinnet (BNC Connector and RG-58) Twisted Pair Cable Category 1 – Category 6 RJ-11 and RJ-45 Connectors Fiber Optic Cable

72. Coaxial Cable Contains a center conductor, made of copper, surrounded by a plastic jacket Teflon type covering  plenum-rated coating does not burn easily Coax is not used in LANs today but still used widely by TV cable operators

73. Thin Ethernet Thinnet 10Base-2 Thin coaxial cable– smaller than thick coaxial cable

74. A Stripped-back Thinnet

75. Thinnet

76. Connectors With thinnet, you use BNC (BayoNet Connector) connectors to attach stations to the network. BNC Connector locks securely with a quarter-twist motion A T-connector is used to connect backbone devices

77. Male and Female BNC Connectors

79. F type connector Popular with TV Cable and Cable Modems

80. Twisted-pair cable Consists of multiple, individually insulated wires that are twisted together in pairs Sometimes a metallic shield is placed around pairs shielded twisted pair (STP) Unshielded twisted pair (UTP)

81. Why twisted? Electromagnetic signals create interference  crosstalk Twisting the cables in pairs reduce intereference Most common cable

82. Twisted-pair Cheaper Easy to work with Transmission rates are good

83. Fiber Optic Cable 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

85. Greatly increased bandwidth and capacity

86. Lower signal loss

87. Immunity to Electrical Noise

88. Immune to noise (electromagnetic interference [EMI] and radio-frequency interference [RFI]

89. Lower bit error rates

90. Signal Security

91. Difficult to tap

93. Network Topologies The manner in which workstations are connected together physically and logically is referred to as a NETWORK TOPOLOGY. 4 Types: Bus (Video) Ring (Video) Star (Video) Hybrid

95. BUS Topology Information transfer Terminators Setup is simple Expansion Repair Cost

97. STAR Topology Central network connector (switch) Less than 100m. Expansion—switch-uplink Troubleshooting Cost—cable

99. Ring Topology Information flows one way Close together Expansion Troubleshooting Cost

101. Hybrid Topology

102. Why Hybrid (Tiered)? Reliability—less service interruption Capacity- not easily saturated Cost – low cost networks can build up Needs- not every department need the same equipment (accounting vs. graphics)

105. The five basic functions of network management are:Fault management Configuration management Performance management Security Management Accounting Management

106. Chapter 4 The End