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 Clients2

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 Clients3

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 Clients4

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 Clients5

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 Clients6

7. Chapter 5: Communications Media, Servers, and Clients7

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 Clients8

9. Chapter 5: Communications Media, Servers, and Clients9

10. Chapter 5: Communications Media, Servers, and Clients10

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 Clients11

12. Chapter 5: Communications Media, Servers, and Clients12

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 Clients13

14. Chapter 5: Communications Media, Servers, and Clients14

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 Clients15

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 Clients16

17. Chapter 5: Communications Media, Servers, and Clients17

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 Clients18

19. Chapter 5: Communications Media, Servers, and Clients19

20. Chapter 5: Communications Media, Servers, and Clients20

21. Chapter 5: Communications Media, Servers, and Clients21

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 Clients22

23. Chapter 5: Communications Media, Servers, and Clients23

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 Clients24

25. Chapter 5: Communications Media, Servers, and Clients25

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 Clients26

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 Clients27

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 Clients28

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 Clients29

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 Clients30

31. Chapter 5: Communications Media, Servers, and Clients31

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 Clients32

33. Chapter 5: Communications Media, Servers, and Clients33

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 Clients34

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 Clients35

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 Clients36

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 Clients37

38. Chapter 5: Communications Media, Servers, and Clients38

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 Clients39

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 Clients40

41. Chapter 5: Communications Media, Servers, and Clients41

42. Chapter 5: Communications Media, Servers, and Clients42

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 Clients43

44. Chapter 5: Communications Media, Servers, and Clients44

45. Chapter 5: Communications Media, Servers, and Clients45

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 Clients46

47. Chapter 5: Communications Media, Servers, and Clients47

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 Clients48

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 Clients49

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 Clients50

51. Chapter 3 Complete