1. CEG 2400 FALL 2012 Chapter 3 Transmission Basics and Networking Media 1

2. Transmission Basics Transmit –Issue signals along network medium Transmission –Process of transmitting –Signal progress after transmitting Transceiver –Transmits and receives signals 2

3. Analog and Digital Signaling Important data transmission characteristic –Signaling type: analog or digital Volt –Measure of electrical current pressure Voltage = Electrical signal strength Signal Types –Current, light pulses, electromagnetic waves 3

4. Analog and Digital Signaling (cont’d.) Analog data signals –Voltage varies continuously Fundamental properties of analog signals –Amplitude Measure of strength at given point in time –Frequency Number of times amplitude cycles over fixed time –Wavelength Distance between one peak and the next –Phase Progress of wave over time compared to a fixed point 4

5. 5 An example of an analog signal Wavelength Frequency

6. 6 Waves with a 90 degree phase difference Phase

7. Analog and Digital Signaling (cont’d.) Analog signal benefit over digital –Conveys greater subtleties with less energy Drawback of analog signals –Susceptible to transmission flaws Digital signals –Pulses of voltages Positive voltage represents a 1 Zero voltage represents a 0 7

8. 8 An example of a digital signal Components of a byte

9. Analog and Digital Signaling (cont’d.) Convert byte to decimal number –Determine value represented by each bit –Add values = Decimal number Convert decimal number to a byte –Reverse the process Convert between binary and decimal –Can be done by hand or calculator –For class learn by hand 9

10. Analog and Digital Signaling (cont’d.) Digital signal benefits over analog signal –More reliable –Less severe noise interference Digital signal drawback –Many pulses required to transmit same amount of information –More overhead than analog Nondata information Required for proper signal routing and interpretation 10

11. Data Modulation Data modulation –Technology modifying analog signals –Make data suitable for carrying over communication path Used if data relies on digital transmission and network connection may handle only analog signals Device - Modem –Accomplishes translation –Modulator/demodulator 11

12. Data Modulation (cont’d.) Carrier wave –Combined with another analog signal to produce a unique signal Transmitted from one node to another Information wave (data wave) –Added to carrier wave –Modifies one carrier wave property Result – Blended wave 12

13. Data Modulation (cont’d.) Frequency modulation (FM) –Carrier frequency modified by application of data signal Amplitude modulation (AM) –Carrier signal amplitude modified by application of data signal EX. Digital subscriber line (DSL) –Makes use of modulation 13

14. 14 A carrier wave modified through frequency modulation

15. Kinds of Transmission Simplex, Half-Duplex, and Duplex Simplex –Signals travel in one direction Half-duplex transmission –Signals travel in both directions one way at a time –Shared communication channel Full-duplex –Signals travel in both directions simultaneously –Used on data networks –Increases speed of data travel 15

16. 16 Simplex, half-duplex, and full-duplex transmission

17. Multiplexing –Multiple signals travel simultaneously over one medium –Subchannels - Logical multiple smaller channels Multiplexer (mux) –Combines many channel signals Demultiplexer (demux) –Separates combined signals and regenerates them 17

18. Types of Multiplexing Time division multiplexing (TDM) –Divides channel into multiple time intervals – not efficient 18 Time division multiplexing

19. Types of Multiplexing (cont’d.) Statistical multiplexing –Transmitter assigns slots to nodes According to priority, need –More efficient than Time division multiplexing 19 Statistical multiplexing

20. Types of Multiplexing (cont’d.) Frequency division multiplexing (FDM) –Unique frequency band for each communications subchannel –Cellular telephone transmission –DSL Internet access 20 Frequency division multiplexing

21. Types of Multiplexing (cont’d.) Wavelength division multiplexing (WDM) –One fiber-optic connection –Carries multiple light signals simultaneously 21 Wavelength division multiplexing

22. Types of Multiplexing (cont’d.) Dense wavelength division multiplexing (DWDM) –Similar to Wavelength division multiplexing (WDM) –Used on most modern fiber-optic networks –Extraordinary capacity –WDM – up to 40 channels –DWDM – up to160 channels 22

23. Relationships Between Nodes Point-to-Point transmission –One transmitter and one receiver Point-to-Multipoint transmission –One transmitter and multiple receivers –Two Types Broadcast transmission –One transmitter and multiple, undefined receivers Nonbroadcast –One transmitter and multiple, defined recipients 23

24. 24 Point-to-point versus broadcast transmission

25. Throughput and Bandwidth Throughput –Amount of data transmitted during given time period –Also called capacity or bandwidth –Expressed as bits transmitted per second Bandwidth (strict definition) –Difference between highest and lowest frequencies medium can transmit measured in hertz (Hz) 25

26. 26 Throughput measures

27. Baseband and Broadband Baseband transmission –Digital signals sent through direct current (DC) pulses applied to wire –Requires exclusive use of wire’s capacity –Transmit one signal (channel) at a time –Example: Ethernet Broadband transmission –Signals modulated as radio frequency (RF) analog waves –Uses different frequency ranges –Does not encode information as digital pulses –Example: Cable TV –Broadband can have different meanings! 27

28. Transmission Flaws Transmission Flaws – transmission degrades between sender and receiver 1. Noise –Any undesirable influence degrading or distorting signal –Types of noise EMI (electromagnetic interference) –Example: Motors, power lines, magnets Cross talk –Signal on one wire infringes on adjacent wire signal 28

29. 29 Cross talk between wires in a cable

30. Transmission Flaws (cont’d.) 2. Attenuation –Loss of signal’s strength as it travels away from source –Signal boosting technology Analog signals pass through amplifier –Noise also amplified Regeneration –Digital signals retransmitted in original form –Repeater: device regenerating digital signals 30

31. 31 A digital signal distorted by noise and then repeated An analog signal distorted by noise and then amplified

32. Transmission Flaws (cont’d.) 3. Latency –Delay between signal transmission and receipt –May cause network transmission errors –Latency causes Cable length Intervening connectivity device 32

33. Common Media Characteristics Physical media characteristics 1.Throughput 2.Cost 3.Noise immunity 4.Size and scalability 5.Connectors and media converters 33

34. Throughput Causes of throughput limitations –Laws of physics –Signaling and multiplexing techniques used –Noise –Devices connected to transmission medium Most significant factor in choosing transmission method 34

35. Cost Precise costs difficult to pinpoint Media cost dependencies –Existing hardware, network size, labor costs Some variables influencing final cost –Installation cost –New infrastructure cost versus reuse –Maintenance and support costs –Cost of lower transmission rate affecting productivity –Cost of downtime –Cost of obsolescence 35

36. Noise Immunity Noise distorts data signals –Distortion rate dependent upon transmission media Limit noise impact on network –Cable installation Far away from powerful electromagnetic forces –Select media protecting signal from noise Fiber-optic: least susceptible to noise 36

37. Size and Scalability Three specifications 1.Maximum nodes per segment 2.Maximum segment length 3.Maximum network length Maximum nodes per segment –Each device adds attenuation and latency 37

38. Size and Scalability (cont’d.) Maximum segment length –Attenuation and latency plus segment type Segment types –Populated: contains end nodes –Unpopulated: no end nodes Segment length limitation –After certain distance, signal loses strength Maximum network length –Same as segment length except it is the sum of the network’s segments lengths 38

39. Connectors and Media Converters Connectors –Hardware connecting wire to network device Piece on end of wire Media converter –Hardware enabling networks or segments running on different media to interconnect and exchange signals 39

40. 40 Copper wire-to-fiber media converter

41. Types of Cables Coaxial STP (Shielded Twisted Pairs) UTP (Unshielded Twisted Pairs) Fiber-Optic 41

42. Coaxial Cable Central metal core (often copper) surrounded by: –Insulator –Braided metal shielding (braiding or shield) –Outer cover (sheath or jacket) 42 Coaxial cable

43. Coaxial Cable (cont’d.) High noise resistance Advantage over twisted pair –Carry signals farther before amplifier required Disadvantage over twisted pair cabling –More expensive 43

44. Coaxial Cable (cont’d.) Hundreds of specifications –RG specification number Data networks –RG-6 (Cable TV) –RG-8 (Thicknet) –RG-58 (Thinnet) –RG-59 (used for short distant) Differences: shielding and conducting cores –Conducting core American Wire Gauge (AWG) size –Larger AWG size, smaller wire diameter 44

45. Twisted Pair Cable Color-coded insulated copper wire pairs –0.4 to 0.8 mm diameter –Encased in a plastic sheath 45 Twisted pair cable

46. Twisted Pair Cable (cont’d.) More wire pair twists per foot –More resistance to cross talk –Higher-quality –More expensive Twist ratio –Twists per meter or foot 46

47. Twisted Pair Cable (cont’d.) Hundreds of different designs –Twist ratio, number of wire pairs, copper grade, shielding type, shielding materials –1 to 4200 wire pairs possible Most common twisted pair types –Category (cat) 3, 5, 5e, 6, 6a, 7 –CAT 5 or higher used in modern LANs 47

48. Twisted Pair Cable (cont’d.) Advantages –Relatively inexpensive –Flexible –Easy installation Two categories –Shielded twisted pair (STP) –Unshielded twisted pair (UTP) 48

49. STP (Shielded Twisted Pair) Individually insulated Surrounded by metallic substance shielding (foil) –Barrier to external electromagnetic forces –Contains electrical energy of signals inside 49 STP cable

50. UTP (Unshielded Twisted Pair) One or more insulated wire pairs –Encased in plastic sheath –No additional shielding Less expensive, less noise resistance 50 UTP cable

51. Terminating Twisted Pair Cable Patch cable –Relatively short cable –Connectors at both ends TIA/EIA standards –TIA/EIA 568A –TIA/EIA 568B 51

52. 52 TIA/EIA 568A standard terminationsTIA/EIA 568B standard terminations

53. Terminating Twisted Pair Cable (cont’d.) Straight-through cable (ex. Patch cable) –Terminate RJ-45 plugs at both ends identically Crossover cable –Transmit and receive wires on one end reversed 53 RJ-45 terminations on a crossover cable

54. Fiber-Optic Cable Fiber-optic cable (fiber) –One or more glass or plastic fibers at its center (core) Data transmission –Pulsing light sent from laser or light-emitting diode (LED) through central fibers Cladding (surrounds fiber) –Layer of glass or plastic surrounding fibers –Different density from glass or plastic in strands –Reflects light back to core –Allows fiber to bend 54

55. Fiber-Optic Cable (cont’d.) Plastic buffer outside cladding –Protects cladding and core –Opaque to absorb escaping light –Surrounded by Kevlar (polymeric fiber) strands Plastic sheath covers Kevlar strands 55 A fiber-optic cable

56. Fiber-Optic Cable (cont’d.) Benefits over copper cabling –Extremely high throughput –Very high noise resistance –Excellent security –Able to carry signals for longer distances Drawbacks –More expensive than twisted pair cable –Requires special equipment to splice Two Types –Single-mode and Multimode 56

57. SMF (Single-Mode Fiber) Consists of narrow core (8-10 microns in diameter) –Laser-generated light travels over one path Little reflection –Light does not disperse as signal travels Can carry signals many miles before repeating required Rarely used for shorter connections due to cost 57

58. MMF (Multimode Fiber) Larger diameter core than single-mode fiber –Common sizes: 50 or 62.5 microns Laser or LED generated light pulses travel at different angles Common uses –Cables connecting router to a switch –Cables connecting server on network backbone 58

59. Serial Cables Used to connect to a device such as router or switch Data transmission style –Pulses issued sequentially, not simultaneously Serial transmission method –RS-232 standard Uses DB-9, DB-25, and RJ-45 connectors 59

60. Structured Cabling Cable plant –Hardware that makes up the entire enterprise cabling system Cabling standard –TIA/EIA’s joint 568 Commercial Building Wiring Standard Also known as structured cabling 60

61. Structured Cabling (cont’d.) Components 1.Entrance facilities 2.MDF (main distribution frame) 3.Cross-connect facilities (Punch-down, Patch panel) 4.IDF (intermediate distribution frame) 5.Backbone wiring 6.Telecommunications closet 7.Horizontal wiring 8.Work area 61

62. TIA/EIA structured cabling in an enterprise Horizontal wiring

63. Summary Information transmission methods –Analog –Digital Multiplexing allows multiple signals to travel simultaneously over one medium Full and half-duplex specifies whether signals can travel in both directions or one direction at a time Noise distorts both analog and digital signals Attenuation –Loss of signal as it travels 63

64. Summary (cont’d.) Coaxial cable composed of core, insulator, shielding, sheath Types of twisted pair cable –Shielded and unshielded Fiber-optic cable transmits data through light passing through the central fibers 64

65. Summary (cont’d.) Fiber-optic cable categories –Single and multimode fiber Serial communication often used for short connections between devices Structured cabling standard provides wiring guidelines 65

66. Testing Internet Bandwidth http://www.speedtest.net http://www.speakeasy.net/speedtest/ http://www.att.com/speedtest/ http://www.bandwidthplace.com/ Wideband is the next generation of Internet and is considered to be faster than broadband. 66

67. WideBand Most people have become familiar with the term broadband internet but not as many are familiar with the term wideband internet. Wideband was a term that has previously been used in conjunction with radio and television frequencies, not the internet. That has changed in the last couple of years and you will begin hearing it more and more in the future. Just as broadband has come to mean faster, smoother internet connections that took the consumer to the next level beyond dial-up, wideband is a term that refers to the next step beyond broadband. It provides more than just a higher speed connection, but a whole new level of interaction. 67

68. End of Chapter 3 Questions 68