6 th Edition Chapter 3 Transmission Basics and Networking Media Objectives Explain basic data transmission concepts including full duplexing attenuation latency and noise Describe the physical characteristics of coaxial cable STP UTP and fiberoptic media ID: 739868
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Network+ Guide to Networks6th Edition
Chapter 3
Transmission Basics and Networking MediaSlide2
ObjectivesExplain basic data transmission concepts, including full duplexing, attenuation, latency, and noise
Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media
Compare the benefits and limitations of different networking media
Explain the principles behind and uses for serial cablesIdentify wiring standards and the best practices for cabling buildings and work areas
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Transmission BasicsTransmit
Issue signals along network medium
Transmission
Process of transmittingSignal progress after transmittingTransceiverTransmits and receives signals
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Analog and Digital SignalingImportant data transmission characteristic
Signaling type: analog or digital
Volt
Electrical current pressureElectrical signal strengthDirectly proportional to voltage
Signal voltageSignalsCurrent, light pulses, electromagnetic waves
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Analog and Digital Signaling (cont’d.)
Analog data signals
Voltage varies continuously
Fundamental properties of analog signalsAmplitudeMeasure of strength at given point in timeFrequency
Number of times amplitude cycles over fixed timeWavelengthDistance between one peak and the nextPhaseProgress of wave over time compared to a fixed point
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Figure
3-1 An example of an analog signal
Courtesy Course Technology/Cengage LearningSlide7
Analog and Digital Signaling (cont’d.)Analog signal benefit over digital
More variable
Convey greater subtleties with less energy
Drawback of analog signalsVaried and imprecise voltageSusceptible to transmission flaws
Digital signalsPulses of voltagesPositive voltage represents a 1Zero voltage represents a 0
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Analog and Digital Signaling (cont’d.)Digital signal benefit over analog signal
More reliable
Less severe noise interference
Digital signal drawbackMany pulses required to transmit same informationOverhead
Nondata information Required for proper signal routing and interpretationExample: network layer addressing information
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Data ModulationData relies on digital transmission
Network connection may handle only analog signals
Modem
Accomplishes translationModulator (analog to digital)Demodulator (digital to analog)
Data modulationTechnology modifying analog signalsMake data suitable for carrying over communication path
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Simplex, Half-Duplex, and Duplex
Simplex
Signals travel in one direction
Half-duplex transmissionSignals travel in both directionsOne at a timeShared communication channel
Full-duplexSignals travel in both directions simultaneouslyUsed on data networks
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MultiplexingMultiplexing
Multiple signals
Travel simultaneously over one medium
SubchannelsLogical multiple smaller channels
Multiplexer (mux)Combines many channel signalsDemultiplexer (demux)Separates combined signalsRegenerates them
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Multiplexing (cont’d.)
T
ime
division multiplexing (TDM) - telephonyDivides channel into multiple time intervals
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Courtesy Course Technology/Cengage Learning
Figure
3-7 Time division multiplexingSlide14
Multiplexing (cont’d.)
Frequency division multiplexing (FDM
) – cable TV
Unique frequency band for each communications subchannelCellular telephone transmission
DSL Internet accessNetwork+ Guide to Networks, 6
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Courtesy Course Technology/Cengage Learning
Figure
3-9 Frequency division multiplexingSlide15
Multiplexing (cont’d.)
Wavelength division multiplexing (WDM)
One
fiber-optic connectionCarries multiple light signals simultaneously
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Courtesy Course Technology/Cengage Learning
Figure
3-10 Wavelength division multiplexingSlide16
Relationships Between NodesPoint-to-point transmission
One transmitter and one receiver
Point-to-multipoint transmission
One transmitter and multiple receiversBroadcast transmissionOne transmitter and multiple, undefined receivers
Used on wired and wireless networksSimple and quickNonbroadcastOne transmitter and multiple, defined recipients
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Courtesy Course Technology/Cengage Learning
Figure
3-11 Point-to-point versus broadcast transmissionSlide18
Throughput and BandwidthThroughput
Amount of data transmitted during given time period
Also called capacity or bandwidth
Expressed as bits transmitted per secondBandwidth (strict definition)Difference between highest and lowest frequencies medium can transmit
Range of frequenciesMeasured in hertz (Hz)
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Courtesy Course Technology/Cengage Learning
Table 3-1 Throughput measuresSlide20
Baseband and Broadband
Baseband transmission
Digital signals sent through direct current (DC) pulses applied to wire
Requires exclusive use of wire’s capacityTransmit one signal (channel) at a time
Example: EthernetBroadband transmissionSignals modulated as radio frequency (RF) analog wavesUses different frequency rangesDoes not encode information as digital pulses
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Transmission Flaws
Noise
Any undesirable influence degrading or distorting signal
Types of noiseEMI (electromagnetic interference)Example: radio frequency interference
Cross talkSignal on one wire infringes on adjacent wire signalNear end cross talk (NEXT) occurs near source
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Courtesy Course Technology/Cengage Learning
Figure 3-12 Cross talk between wires in a cableSlide23
Transmission Flaws (cont’d.)
Attenuation
Loss of signal’s strength as it travels away from source
Signal boosting technologyAnalog signals pass through amplifierNoise also amplified
RegenerationDigital signals retransmitted in original formRepeater: device regenerating digital signalsAmplifiers and repeatersOSI model Physical layer
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Transmission Flaws (cont’d.)LatencyDelay between signal transmission and receipt
May cause network transmission
errors
Latency causesCable lengthIntervening connectivity deviceRound trip time (RTT)Time for packet to go from sender to receiver, then back from receiver to sender
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Common Media CharacteristicsSelecting transmission media
Match networking needs with media characteristics
Physical media characteristics
ThroughputCostNoise immunitySize and scalabilityConnectors and media converters
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ThroughputMost significant factor
in choosing transmission
method
Causes of throughput limitationsLaws of physicsSignaling and multiplexing techniquesNoiseDevices connected to transmission medium
Fiber-optic cables allow faster throughput Compared to copper or wireless connections
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CostPrecise costs difficult to pinpointMedia cost dependencies
Existing hardware, network size, labor costs
Variables influencing final cost
Installation costNew infrastructure cost versus reuseMaintenance and support costsCost of lower transmission rate affecting productivity
Cost of downtimeCost of obsolescenceNetwork+ Guide to Networks, 6th Edition
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Noise ImmunityNoise distorts data signals
Distortion rate dependent upon transmission media
Fiber-optic: least susceptible to noise
Limit noise impact on networkCable installationFar away from powerful electromagnetic forces
Select media protecting signal from noiseAntinoise algorithms
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Size and ScalabilityThree specifications
Maximum nodes per segment
Maximum segment length
Maximum network lengthMaximum nodes per segment dependencyAttenuation and latencyMaximum segment length dependency
Attenuation and latency plus segment typeNetwork+ Guide to Networks, 6
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Size and Scalability (cont’d.)Segment types
Populated: contains end nodes
Unpopulated: no end nodes
Also called link segmentSegment length limitationAfter certain distance, signal loses strength
Cannot be accurately interpretedNetwork+ Guide to Networks, 6th
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Connectors and Media ConvertersConnectors
Hardware connecting wire to network device
Specific to particular media type
Affect costsInstalling and maintaining networkEase of adding new segments or nodes
Technical expertise required to maintain networkMedia converterHardware enabling networks or segments running on different media to interconnect and exchange signals
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Courtesy of Omnitron Systems Technology
Figure
3-15 Copper wire-to-fiber media converterSlide34
Coaxial CableCentral metal core (often copper) surrounded by:
I
nsulator
Braided metal shielding (braiding or shield)Outer cover (sheath or jacket)
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Figure
3-16 Coaxial cable
Courtesy Course Technology/Cengage LearningSlide35
Coaxial Cable (cont’d.)High noise resistanceAdvantage over twisted pair cabling
Carry signals farther before amplifier required
Disadvantage over twisted pair cabling
More expensiveHundreds of specificationsRG specification numberDifferences: shielding and conducting cores
Transmission characteristicsNetwork+ Guide to Networks, 6th Edition
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Courtesy of MCM Electronics, Inc.
Figure
3-17 F-Type connector
© Igor Smichkov/Shutterstock.com
Figure
3-18 BNC connectorSlide37
Twisted Pair CableColor-coded insulated copper wire pairs
0.4 to 0.8 mm diameter
Encased in a plastic sheath
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Courtesy Course Technology/Cengage Learning
Figure
3-19 Twisted pair cableSlide38
Twisted Pair Cable (cont’d.)More wire pair twists per foot
More resistance to cross talk
Higher-quality
More expensiveTwist ratioTwists per meter or footHigh twist ratio
Greater attenuationNetwork+ Guide to Networks, 6
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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
Wiring standard specificationTIA/EIA 568Most common twisted pair types
Category (cat) 3, 5, 5e, 6, 6a, 7CAT 5 or higher used in modern LANs
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Twisted Pair Cable (cont’d.)Advantages
Relatively inexpensive
Flexible
Easy installationSpans significant distance before requiring repeaterAccommodates several different topologies
Two categoriesShielded twisted pair (STP)Unshielded twisted pair (UTP)
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STP (Shielded Twisted Pair)Individually insulated
Surrounded by metallic substance shielding (foil)
Barrier to external electromagnetic forces
Contains electrical energy of signals insideMay be grounded
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Figure
3-20 STP cable
Courtesy Course Technology/Cengage LearningSlide42
UTP (Unshielded Twisted Pair)One or more insulated wire pairs
Encased in plastic sheath
No additional shielding
Less expensive, less noise resistance
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Courtesy Course Technology/Cengage Learning
Figure
3-21
U
TP cableSlide43
Comparing STP and UTPThroughputSTP and UTP can transmit the same rates
Cost
STP and UTP vary
ConnectorSTP and UTP use Registered Jack 45Telephone connections use Registered Jack 11
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Comparing STP and UTP (cont’d.)Noise immunity
STP more noise resistant
Size and scalability
Maximum segment length for both: 100 meters
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Terminating Twisted Pair Cable
Patch cable
Relatively short cable
Connectors at both endsProper cable termination techniquesBasic requirement for two nodes to communicate
Poor terminations:Lead to loss or noiseTIA/EIA standardsTIA/EIA 568ATIA/EIA 568B
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Courtesy Course Technology/Cengage Learning
Figure
3-24 TIA/EIA 568A standard terminations
Courtesy Course Technology/Cengage Learning
Figure
3-25 TIA/EIA 568B standard terminationsSlide47
Terminating Twisted Pair Cable (cont’d.)
Straight-through cable
Terminate RJ-45 plugs at both ends identically
Crossover cableTransmit and receive wires on one end reversed
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Figure
3-26 RJ-45 terminations on a crossover cable
Courtesy Course Technology/Cengage LearningSlide48
Fiber-Optic CableFiber-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
CladdingLayer of glass or plastic surrounding fibersDifferent density from glass or plastic in strandsReflects light back to coreAllows fiber to bend
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Fiber-Optic Cable (cont’d.)Plastic buffer outside cladding
Protects cladding and core
Opaque to absorb escaping light
Surrounded by Kevlar (polymeric fiber) strandsPlastic sheath covers Kevlar strands
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Figure
3-30 A fiber-optic cable
Courtesy of Optical Cable CorporationSlide50
Fiber-Optic Cable (cont’d.)Benefits over copper cabling
Extremely high throughput
Very high noise resistance
Excellent securityAble to carry signals for longer distancesIndustry standard for high-speed networkingDrawbacksMore expensive than twisted pair cable
Requires special equipment to spliceNetwork+ Guide to Networks, 6th Edition50Slide51
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 travelsCan carry signals many miles:Before repeating required
Rarely used for shorter connectionsDue to cost
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MMF (Multimode Fiber)Contains core with larger diameter than single-mode fiber
Common sizes: 50 or 62.5 microns
Laser or LED generated light pulses travel at different angles
Greater attenuation than single-mode fiberCommon usesCables connecting router to a switch
Cables connecting server on network backboneNetwork+ Guide to Networks, 6
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Figure
3-42 TIA/EIA structured cabling in an enterprise
Courtesy Course Technology/Cengage LearningSlide54
Structured Cabling (cont’d.)
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Table 3-2 TIA/EIA specifications for backbone cabling
Courtesy Course Technology/Cengage LearningSlide55
SummaryInformation transmission methods
Analog
Digital
Multiplexing allows multiple signals to travel simultaneously over one mediumFull and half-duplex specifies whether signals can travel in both directions or one direction at a timeNoise distorts both analog and digital signals
AttenuationLoss of signal as it travels
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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
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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
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