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Business Data Communications, Fourth Edition

Business Data Communications, Fourth Edition. Chapter 3: Communications Media, Servers, and Clients. Learning Objectives. Describe the difference between guided media and unguided media Define twisted pair wire, coaxial cable, and fiber optic cable

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Business Data Communications, Fourth Edition

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  1. Business Data Communications, Fourth Edition Chapter 3: Communications Media, Servers, and Clients

  2. Learning Objectives • Describe the difference between guided media and unguided media • Define twisted pair wire, coaxial cable, and fiber optic cable • Describe how different types of cables are used in networks • List five forms of transmission that use unguided media • Describe the difference between microwave and broadcast radio Chapter 5: Communications Media, Servers, and Clients 2

  3. Learning Objectives • Identify the advantages of one medium over another in terms of cost, speed, and data reliability • Describe the use of various types of computers in a communications system • Explain the differences among servers and various types of clients • Describe the line configurations used to connect terminals in a network Chapter 5: Communications Media, Servers, and Clients 3

  4. Learning Objectives • Explain how computers and modems communicate using RS-232 connectors • List applications of the RS-449, Universal Serial Bus, and FireWire standards Chapter 5: Communications Media, Servers, and Clients 4

  5. Introduction • Devices on a network are connected using a medium • Physical wire – guided medium • Wireless – unguided medium • Cost and performance differ among the types of media Chapter 5: Communications Media, Servers, and Clients 5

  6. Guided Media • Twisted Pair Wire • Insulated copper wire, twisted to prevent interference • Unshielded twisted pair (UTP) • No extra insulation • Prone to interference • Used for residential telephones • Shielded twisted pair (STP) • Each pair of wires is in a metallic shield • Good insulation qualities • UTP Categories 1 through 6 Chapter 5: Communications Media, Servers, and Clients 6

  7. Chapter 5: Communications Media, Servers, and Clients 7

  8. Guided Media • Coaxial Cable (Coax) • Better insulation than UTP or STP • Broadband • Many channels on one physical cable • Cable TV • Baseband • One channel (or signal) on one cable • Used in computer networks Chapter 5: Communications Media, Servers, and Clients 8

  9. Chapter 5: Communications Media, Servers, and Clients 9

  10. Chapter 5: Communications Media, Servers, and Clients 10

  11. Guided Media • Fiber Optic Cable • Construction of fiber • Very pure glass or plastic • Outer sheathing to bundle the fibers • How data is transmitted • Uses a light source • Light-emitting diode (LED) • Laser Chapter 5: Communications Media, Servers, and Clients 11

  12. Chapter 5: Communications Media, Servers, and Clients 12

  13. Guided Media • Fiber Optic Cable • Multimode step index • Light bounces off the walls of the sheathing • Multimode graded index • Cable core varies in density, light bent at more shallow angles • Single-mode cable • Light travels in a straight line, due to very thin core Chapter 5: Communications Media, Servers, and Clients 13

  14. Chapter 5: Communications Media, Servers, and Clients 14

  15. Guided Media • Fiber Optic Cable • Problems with transmission of light • Attenuation – loss of signal • Dispersion – spreading of signal • Interference • Better protection than copper wires • No crosstalk occurs Chapter 5: Communications Media, Servers, and Clients 15

  16. Unguided Media • Wireless media • Broadcast radio • Omnidirectional transmission • Signals send over range of frequencies • Radio broadcast • Shortwave, citizen band • Ultrahigh frequency, very high frequency • High definition television (HDTV) • Digital Television Technology (DTV) • Digital Radio Chapter 5: Communications Media, Servers, and Clients 16

  17. Chapter 5: Communications Media, Servers, and Clients 17

  18. Unguided Media • Microwave • Unidirectional transmission • Terrestrial microwave • Satellite microwave • Geosynchronous Earth orbiting satellite (GEOS) • Satellite footprint • Transponder (uplinks, downlinks) • Propagation delay • Low Earth orbiting satellite (LEOS) • Medium Earth orbiting satellite (MEOS) Chapter 5: Communications Media, Servers, and Clients 18

  19. Chapter 5: Communications Media, Servers, and Clients 19

  20. Chapter 5: Communications Media, Servers, and Clients 20

  21. Chapter 5: Communications Media, Servers, and Clients 21

  22. Radiated Media • Microwave • Satellite microwave • Mobile satellite service (MSS) • Two-way voice and data communication • Global Mobile Personal Communications by Satellite (GMPCS) • Early warning for emergencies • Direct broadcast satellites • DirectTV • Global positioning system (GPS) • Triangulation method to determine spot on earth • Used in autos, boats, planes, golf carts Chapter 5: Communications Media, Servers, and Clients 22

  23. Chapter 5: Communications Media, Servers, and Clients 23

  24. Unguided Media • Cellular Radio • Cellular telephones • Broadcast area • Cells • Antenna in each cell • Used for voice and data • Transmissions can be picked up by scanners • Cloning occurs less frequently now Chapter 5: Communications Media, Servers, and Clients 24

  25. Chapter 5: Communications Media, Servers, and Clients 25

  26. Unguided Media • Spread Spectrum Radio • Spreads radio transmission over a range rather over a narrow frequency • Any device in the area can pick up the signal • Frequency-hopping spread spectrum • Signal hops over a series of frequencies • Devices must be synchronized • Direct sequence spread spectrum • Signal is broadcast on several frequencies simultaneously • Chip is added to identify the transmission to devices • Several users can use the same frequency • LANs use DSSS Chapter 5: Communications Media, Servers, and Clients 26

  27. Unguided Media • Infrared Transmission • Light signals sent at a frequency that cannot be seen • Used in remote controls • IrDA ports used with printers, keyboards, mouse • LANs use this for wireless transmission Chapter 5: Communications Media, Servers, and Clients 27

  28. Selection of Media • Cost • UTP is least expensive • Fiber optic cable most expensive • Speed • UTP slowest • Fiber Optic cable is fastest • Rate of Errors • Security Chapter 5: Communications Media, Servers, and Clients 28

  29. Computers and Terminals in a Communications Network • Computers in a Network • Wide Area Network (WAN) • Covers large geographic area • Local Area Network (LAN) • Limited geographic area • Computers are nodes on a network • Server – controlling computer • Client – many types of devices that use information on the server Chapter 5: Communications Media, Servers, and Clients 29

  30. Computers and Terminals in a Communications Network • Mainframe Computers and Supercomputers • Host Computers • Accessed by many terminals • Acts as a server in a network • Used in WANs and LANs • Supercomputers • Weather forecasting, space travel • Universities and the government generally own them Chapter 5: Communications Media, Servers, and Clients 30

  31. Chapter 5: Communications Media, Servers, and Clients 31

  32. Computers and Terminals in a Communications Network • Midrange computers • Smaller and slower than mainframe • May be used as a server • Used in WANs and LANs • Departmental computing • Personal Computers • May be a server or a client • Extremely versatile Chapter 5: Communications Media, Servers, and Clients 32

  33. Chapter 5: Communications Media, Servers, and Clients 33

  34. Computers and Terminals in a Communications Network • Clients (Terminals) • Device for input/output • Dumb terminals • No processing or storage capability • No buffers • Operates in uncontrolled mode • Asynchronous transmission • Smart terminals • Has memory and buffer • Operates in controlled mode • Synchronous transmission Chapter 5: Communications Media, Servers, and Clients 34

  35. Computers and Terminals in a Communications Network • Clients (Terminals) • Intelligent Terminals • Memory • Contains firmware • Operate in controlled mode • Programmable Terminals • Limited memory and processing capability • Can act as stand-alone devices • Less flexible than a PC • Popular before PCs Chapter 5: Communications Media, Servers, and Clients 35

  36. Computers and Terminals in a Communications Network • Clients (Terminals) • X Terminal • Uses X Windows • Graphical client used with TCP/IP or UNIX • Can access many servers simultaneously • Terminal Emulation • Thin-Client (Network) Computer • Used only to connect to a network • Network Personal Computer • Has some memory and storage Chapter 5: Communications Media, Servers, and Clients 36

  37. Computers and Terminals in a Network • Special-Purpose Terminals • Point-of-Sale Terminals • Uses bar code reader to read UPC • Credit Card Authorization Devices • Smart Card • Automated Teller Machines • Airline Reservation Systems Chapter 5: Communications Media, Servers, and Clients 37

  38. Chapter 5: Communications Media, Servers, and Clients 38

  39. Computers and Terminals in a Communications Network • Special-Purpose Terminals • Network Printers • Facsimile Machines • Telephone • Remote Input Clients • Utility use • Rental car agencies • Engineering Industry Clients • CAD/CAM Chapter 5: Communications Media, Servers, and Clients 39

  40. Network Configurations • Configuration is the way servers and clients are connected in a network • Point-to-Point • Direct line between sending and receiving device • Point-to-Point Protocol • Multipoint • Many clients on a shared circuit • Response time is how long a client waits for a response from the server Chapter 5: Communications Media, Servers, and Clients 40

  41. Chapter 5: Communications Media, Servers, and Clients 41

  42. Chapter 5: Communications Media, Servers, and Clients 42

  43. Terminal Interfaces • Interface • How devices are connected to a network • Data Communication Equipment (DCE) • Modems, media, switching equipment • Data Terminal Equipment (DTE) • Clients, servers, concentrators, multiplexers • EIA RS-232F • Interface that connects DCE to DTE • 25-pin electrical connection • Used on a serial port • Compare to parallel port Chapter 5: Communications Media, Servers, and Clients 43

  44. Chapter 5: Communications Media, Servers, and Clients 44

  45. Chapter 5: Communications Media, Servers, and Clients 45

  46. Terminal Interfaces • RS-449 • 37-pin connector • Allows expanded functions • Universal Serial Bus (USB) • Used for low-volume I/O devices • FireWire • High-speed video and audio connections • Handshaking Chapter 5: Communications Media, Servers, and Clients 46

  47. Chapter 5: Communications Media, Servers, and Clients 47

  48. Summary • Three types of guided media • Twisted pair • Coaxial cable • Fiber optic cable • Unguided media use no wires • Radio • Microwave • Infrared Chapter 5: Communications Media, Servers, and Clients 48

  49. Summary • Least expensive is twisted pair • Most expensive is fiber optic cable • Fiber optic transmits at fastest speed • Error rate is lowest on fiber optic cable • Fiber optic cable is the most secure medium Chapter 5: Communications Media, Servers, and Clients 49

  50. Summary • Mainframes, supercomputers, minicomputers, personal computers can be part of a network • Terminals are general-purpose or special-purpose • Point-to-point configurations • Multipoint configurations • Terminals connections - RS-232F or RS-449 • USB and FireWire are new interface standards Chapter 5: Communications Media, Servers, and Clients 50

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