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Exploring Data Transmission Basics and Networking Media Concepts

Learn data transmission concepts, benefits, and limitations of networking media, cabling best practices, and methods for transmitting data. Understand analog vs. digital signals, modulation techniques, throughput, bandwidth, and transmission flaws.

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Exploring Data Transmission Basics and Networking Media Concepts

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  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 progress of data signals over a medium • On a data network, information can be transmitted via one of two methods: • Analog • 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 signal’s strength • Frequency • Number of times a signal’s amplitude changes over a period of time • Expressed in hertz (Hz) • Wavelength • Distances between corresponding points on a wave’s cycle

  7. Transmission Basics • Phase • 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 • Modulation • 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 • Amplitude modulation (AM) • 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 • Half-duplex • Signals may travel in both directions over a medium but in only one direction at a time • Full-duplex • Signals are free to travel in both directions over a medium simultaneously • Also referred to just as duplex

  14. Transmission Direction • Channel • 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 • To accommodate multiple signals, single medium is logically separated into subchannels • 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 Figure 4-7: Time division multiplexing

  17. Transmission Direction • Statistical multiplexing • Similar to TDM • Assigns slots to nodes according to priority and need instead of in succession Figure 4-8: Statistical multiplexing

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

  19. Relationships Between Nodes • Point-to-point • Transmission involving one transmitter and one receiver • Broadcast • Transmission involving one transmitter and multiple receivers • Webcasting • Broadcast transmission used over the Web

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

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

  22. Throughput Table 4-1: Throughput measures

  23. Baseband and Broadband • Baseband • Transmission form in which (typically) digital signals are sent through direct current (DC) pulses applied to the wire • Broadband • Transmission form in which signals are modulated as radiofrequency (RF) pulses that use different frequency ranges

  24. Transmission Flaws • Electromagnetic interference (EMI) • 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

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

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

  27. Transmission Flaws • Attenuation • 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 Figure 4-13: An analog signal distorted by noise, and then amplified

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

  29. Media Characteristics • Throughput • Perhaps most significant factor in choosing a transmission medium is throughput • Cost • Cost of installation • Cost of new infrastructure versus reusing existing infrastructure • Cost of maintenance and support • Cost of a lower transmission rate affecting productivity • Cost of obsolescence

  30. Media Characteristics • Size and scalability • Specifications determining size and scalability: • Maximum nodes per segment • Maximum segment length • Maximum network length • Latency is the delay between the transmission of a signal and its receipt

  31. Media Characteristics • Connectors • Connects wire to network device • Noise immunity • Thicker cables are generally less susceptible to noise • Possible to use antinoise algorithms to protect data from being corrupted by noise • Conduits can protect cabling from noise

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

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

  34. 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

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

  36. Thicknet Characteristics • In Thicknet networking, the transceiver is a separate device and may also be called a media access unit (MAU) Figure 4-16: Thicknet cable transceiver with detail of a vampire tap

  37. Thicknet Characteristics • Attachment Unit Interface (AUI) • 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 Figure 4-17: AUI connectors

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

  39. 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 • Size and scalability • Because of its high noise resistance, it allows data to travel longer than other types of cabling

  40. Thinnet (10Base2) • Also known as thin Ethernet • Characteristics: • Throughput • Can transmit at maximum rate of 10 Mbps • Cost • Less expensive than Thicknet and fiber-optic cable • More expensive than twisted-pair wiring • 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

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

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

  43. 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 ofcrosstalk • Number of twists per meter or foot known as twist ratio • Alien Crosstalk • When signals from adjacent cables interfere with another cable’s transmission Figure 21: Twisted-pair cable

  44. 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

  45. 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

  46. 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

  47. 10BaseT • Popular Ethernet networking standard that replaced 10Base2 and 10Base5 technologies Figure 4-25: A 10BaseT Ethernet network

  48. 10BaseT • Enterprise-wide network • Spans entire organization • Often services needs of many diverse users Figure 4-26: Interconnected 10BaseT segments

  49. 100BaseT • Enables LANs to run at 100-Mbps data transfer rate • Also known as Fast Ethernet • Two 100BaseT specifications have competed for popularity as organizations move to 100-Mbps technology: • 100BaseTX • 100BaseT4

  50. 100BaseVG • Cousin of Ethernet 100 Mbps technologies • VG stands for voice grade • Also called 100VG-AnyLAN • Originally developed by Hewlett-Packard and AT&T • Now governed by IEEE standard 802.12

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