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Chapter Four Transmission Basics and Networking Media.

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Presentation on theme: "Chapter Four Transmission Basics and Networking Media."— Presentation transcript:

1 Chapter Four Transmission Basics and Networking Media

2 Objectives Explain data transmission concepts including full- duplexing, attenuation, and noise Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media Explain the benefits and limitations of different networking media Identify the best practices for cabling buildings and work areas Describe the methods of transmitting data through the atmosphere

3 Transmission Basics Transmission has two meanings: Refers to process of issuing data signals on a medium Refers to process of issuing data signals on a medium Refers to progress of data signals over a medium Refers to progress of data signals over a medium On a data network, information can be transmitted via one of two methods: Analog Analog Digital Digital

4 Transmission Basics Both analog and digital signals are generated by electrical current, pressure of which is measured in volts In analog signals, voltage varies continuously In digital signals, voltage turns off and on repeatedly

5 Transmission Basics Figure 4-1: Example of an analog signal

6 Transmission Basics Amplitude Measure of a signals strength Measure of a signals strengthFrequency Number of times a signals amplitude changes over a period of time Number of times a signals amplitude changes over a period of time Expressed in hertz (Hz) Expressed in hertz (Hz)Wavelength Distances between corresponding points on a waves cycle Distances between corresponding points on a waves cycle

7 Transmission Basics Phase Refers to progress of a wave over time in relationship to a fixed point Refers to progress of a wave over time in relationship to a fixed point Figure 4-2: Phase differences

8 Transmission Basics Figure 4-3: A complex analog signal representing human speech

9 Transmission Basics Binary system encodes using 1s and 0s Bits can only have a value of either 1 or 0 Eight bits together form a byte Noise or any interference that may degrade signals affects digital signals less than analog signals

10 Transmission Basics Figure 4-4: Example of a digital signal

11 Data Modulation Modem Name reflects function as modulator/demodulator Name reflects function as modulator/demodulatorModulation Technique for formatting signals Technique for formatting signals Frequency modulation (FM) Method of data modulation in which frequency of carrier signal is modified by application of a data signal Method of data modulation in which frequency of carrier signal is modified by application of a data signal Amplitude modulation (AM) Modulation technique in which amplitude of carrier signal is modified by application of a data signal Modulation technique in which amplitude of carrier signal is modified by application of a data signal

12 Data Modulation Figure 4-5: A carrier wave modified by frequency modulation

13 Transmission Direction Simplex Signals travel in only one direction Signals travel in only one directionHalf-duplex Signals may travel in both directions over a medium but in only one direction at a time Signals may travel in both directions over a medium but in only one direction at a timeFull-duplex Signals are free to travel in both directions over a medium simultaneously Signals are free to travel in both directions over a medium simultaneously Also referred to just as duplex Also referred to just as duplex

14 Transmission Direction Channel Distinct communication path between two or more nodes Distinct communication path between two or more nodes Figure 4-6: Simplex, half-duplex, and full-duplex transmission

15 Transmission Direction Multiplexing Allows multiple signals to travel simultaneously over one medium Allows multiple signals to travel simultaneously over one medium To accommodate multiple signals, single medium is logically separated into subchannels To accommodate multiple signals, single medium is logically separated into subchannels For each type of multiplexing: For each type of multiplexing: Multiplexer (mux) is required at sending end of channel Demultiplexer (demux) separates the combined signals and regenerates them in original form

16 Transmission Direction Time division multiplexing (TDM) Divides channel into multiple intervals of time Divides channel into multiple intervals of time Figure 4-7: Time division multiplexing

17 Transmission Direction Wavelength division multiplexing (WDM) Used only with fiber-optic cable Used only with fiber-optic cable Data is transmitted as pulses of light Data is transmitted as pulses of light Fiber-optic modem (FOM) is a demultiplexer used on fiber networks that employ WDM Fiber-optic modem (FOM) is a demultiplexer used on fiber networks that employ WDM Figure 4-9: Wavelength division multiplexing

18 Relationships Between Nodes Point-to-point Transmission involving one transmitter and one receiver Transmission involving one transmitter and one receiverBroadcast Transmission involving one transmitter and multiple receivers Transmission involving one transmitter and multiple receiversWebcasting Broadcast transmission used over the Web Broadcast transmission used over the Web

19 Relationships Between Nodes Figure 4-10: Point-to-point versus broadcast transmission

20 Throughput and Bandwidth Throughput is amount of data the medium can transmit during a given period of time Also called capacity Also called capacity Bandwidth measures difference between highest and lowest frequencies a media can transmit Range of frequencies is directly related to throughput Range of frequencies is directly related to throughput

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22 Transmission Flaws Electromagnetic interference (EMI) Interference that may be caused by motors, power lines, television, copiers, fluorescent lights, or other sources of electrical activity Interference that may be caused by motors, power lines, television, copiers, fluorescent lights, or other sources of electrical activity Radiofrequency interference (RFI) Interference that may be generated by motors, power lines, televisions, copiers, fluorescent lights, or broadcast signals from radio or TV towers Interference that may be generated by motors, power lines, televisions, copiers, fluorescent lights, or broadcast signals from radio or TV towers

23 Transmission Flaws Figure 4-11: An analog signal distorted by noise

24 Transmission Flaws Figure 4-12: A digital signal distorted by noise

25 Transmission Flaws Attenuation Loss of signal strength as transmission travels away from source Loss of signal strength as transmission travels away from source Analog signals pass through an amplifier, which increases not only voltage of a signal but also noise accumulated Analog signals pass through an amplifier, which increases not only voltage of a signal but also noise accumulated Figure 4-13: An analog signal distorted by noise, and then amplified

26 Transmission Flaws Regeneration Process of retransmitting a digital signal Process of retransmitting a digital signalRepeater Device used to regenerate a signal Device used to regenerate a signal Figure 4-14: A digital signal distorted by noise, and then repeated

27 Coaxial Cable Consists of central copper core surrounded by an insulator, braiding, and outer cover called a sheath Figure 4-15: Coaxial cable

28 Coaxial Cable Table 4-2: Some types of coaxial cable

29 Thicknet (10Base5) Also called thickwire Ethernet Rigid coaxial cable used on original Ethernet networks IEEE designates Thicknet as 10Base5 Ethernet Almost never used on new networks but you may find it on older networks Used to connect one data closet to another as part of network backbone Used to connect one data closet to another as part of network backbone

30 Thicknet Characteristics Throughput According to IEEE 802.3, Thicknet transmits data at maximum rate of 10 Mbps According to IEEE 802.3, Thicknet transmits data at maximum rate of 10 MbpsCost Less expensive than fiber-optic but more expensive than some other types of coaxial cable Less expensive than fiber-optic but more expensive than some other types of coaxial cableConnector Can include a few different types of connectors, which are very different from those used on modern networks Can include a few different types of connectors, which are very different from those used on modern networks

31 Thicknet Characteristics Attachment Unit Interface (AUI) Ethernet standard establishing physical specifications for connecting coaxial cables with transceivers and networked nodes Ethernet standard establishing physical specifications for connecting coaxial cables with transceivers and networked nodes An AUI connector may also be called a DIX or DB-15 connector An AUI connector may also be called a DIX or DB-15 connector Figure 4-17: AUI connectors

32 Thicknet Characteristics N-series connector (or n connector) Screw-and-barrel arrangement securely connects coaxial cable segments and devices Screw-and-barrel arrangement securely connects coaxial cable segments and devices Figure 4-18: N-Series connector

33 Thicknet Characteristics Noise immunity Because of its wide diameter and excellent shielding, has the highest resistance to noise of any commonly used types of network wiring Because of its wide diameter and excellent shielding, has the highest resistance to noise of any commonly used types of network wiring Size and scalability Because of its high noise resistance, it allows data to travel longer than other types of cabling Because of its high noise resistance, it allows data to travel longer than other types of cabling

34 Thinnet (10Base2) Also known as thin Ethernet Characteristics: Throughput Throughput Can transmit at maximum rate of 10 Mbps Cost Cost Less expensive than Thicknet and fiber-optic cable More expensive than twisted-pair wiring Connectors Connectors Connects wire to network devices with BNC T-connectors A seen in Figure 4-19, BNC barrel connectors are used to join two Thinnet cable segments together

35 Thinnet (10Base2) Characteristics (cont.): Size and scalability Size and scalability Allows a maximum of 185 m per network segment (see Figure 4-20) Noise immunity Noise immunity More resistant than twisted-pair wiring Less resistant than twisted-pair wiring Figure 4-19: Thinnet BNC connectors

36 Thinnet (10Base2) Signal bounce Caused by improper termination on a bus network Caused by improper termination on a bus network Travels endlessly between two ends of network Travels endlessly between two ends of network Prevents new signals from getting through Prevents new signals from getting through Figure 4-20: A 10Base2 Ethernet network

37 Twisted-Pair (TP) Cable Color-coded pairs of insulated copper wires twisted around each other and encased in plastic coating Twists in wire help reduce effects of crosstalk Number of twists per meter or foot known as twist ratio Number of twists per meter or foot known as twist ratio Alien Crosstalk When signals from adjacent cables interfere with another cables transmission When signals from adjacent cables interfere with another cables transmission Figure 21: Twisted-pair cable

38 Shielded Twisted-Pair (STP) STP cable consists of twisted wire pairs that are individually insulated and surrounded by shielding made of metallic substance Figure 4-22: STP cable

39 Unshielded Twisted-Pair Consists of one or more insulated wire pairs encased in a plastic sheath Does not contain additional shielding Figure 4-23: UTP cable

40 Unshielded Twisted-Pair To manage network cabling, it is necessary to be familiar with standards used on modern networks, particularly Category 3 (CAT3) and Category 5 (CAT5) Figure 4-24: A CAT5 UTP cable

41 Comparing STP and UTP Throughput Both can transmit up to 100 Mbps Both can transmit up to 100 MbpsCost Typically, STP is more expensive Typically, STP is more expensiveConnector Both use RJ-45 connectors (see Figure 4-27) and data jacks Both use RJ-45 connectors (see Figure 4-27) and data jacks Noise immunity STP is more noise-resistant STP is more noise-resistant Size and scalability Maximum segment length for both is 100 meters Maximum segment length for both is 100 meters

42 RJ-45 Connector Figure 4-27: An RJ-45 connector

43 Fiber-Optic Cable Contains one or several glass fibers at its core Surrounding the fibers is a layer of glass called cladding Surrounding the fibers is a layer of glass called cladding Figure 4-28: A fiber-optic cable

44 Fiber-Optic Cable Single-mode fiber Carries light pulses along single path Carries light pulses along single path Multimode fiber Many pulses of light generated by LED travel at different angles Many pulses of light generated by LED travel at different angles Figure 4-29: Single-mode and multimode fiber-optic cables

45 Fiber-Optic Cable Throughput Reliable in transmitting up to 1 gigabit per second Reliable in transmitting up to 1 gigabit per secondCost Most expensive type of cable Most expensive type of cable

46 Fiber-Optic Cable Noise immunity Unaffected by either EMI or RFI Unaffected by either EMI or RFI Size and scalability Network segments made from fiber can span 100 meters Network segments made from fiber can span 100 meters Signals transmitted over fiber can experience optical loss Signals transmitted over fiber can experience optical loss

47 Fiber-Optic Cable Two popular connectors used with fiber-optic cable: ST connectors ST connectors SC connectors SC connectors Figure 4-30: ST and SC fiber connectors

48 Atmospheric Transmission Media Infrared transmission Infrared networks use infrared light signals to transmit data through space Infrared networks use infrared light signals to transmit data through space Direct infrared transmission depends on transmitter and receiver remaining within line of sight Direct infrared transmission depends on transmitter and receiver remaining within line of sight In indirect infrared transmission, signals can bounce off of walls, ceilings, and any other objects in their path In indirect infrared transmission, signals can bounce off of walls, ceilings, and any other objects in their path

49 Atmospheric Transmission Media RF transmission Radio frequency (RF) transmission relies on signals broadcast over specific frequencies Radio frequency (RF) transmission relies on signals broadcast over specific frequencies Two most common RF technologies: Two most common RF technologies:Narrowband Spread spectrum

50 Choosing the Right Transmission Media Areas of high EMI or RFI Corners and small spaces DistanceSecurity Existing infrastructure Growth

51 Chapter Summary Information can be transmitted via analog or digital methodology Throughput is the amount of data a medium can transmit during a given period of time Noise is interference that distorts an analog or digital signal Costs depend on many factors There are three specifications that dictate size and scalability of networking media Connectors connect wire to the network device

52 Chapter Summary Coaxial cable consists of central copper core surrounded by an insulator and a sheath Thicknet cabling is a rigid coaxial cable used for original Ethernet networks Both Thicknet and Thinnet coaxial cable rely on bus topology and must be terminated at both ends with a resistor Twisted-pair cable consists of color-coded pairs of insulated copper wires, twisted around each other and encased in plastic coating

53 Chapter Summary STP cable consists of twisted pair wires individually insulated and surrounded by a shielding made of metallic substance UTP cabling consists of one or more insulated wire pairs encased in a plastic sheath Fiber-optic cable contains one or several glass fibers in its core On todays networks, fiber is used primarily as backbone cable


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