Chapter FourChapter FourTransmission Basics and Transmission Basics and
Networking MediaNetworking Media
ObjectivesObjectives
Explain data transmission concepts including full-Explain data transmission concepts including full-duplexing, attenuation, and noiseduplexing, attenuation, and noiseDescribe the physical characteristics of coaxial Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic mediacable, STP, UTP, and fiber-optic mediaExplain the benefits and limitations of different Explain the benefits and limitations of different networking medianetworking mediaIdentify the best practices for cabling buildings and Identify the best practices for cabling buildings and work areaswork areasDescribe the methods of transmitting data through Describe the methods of transmitting data through the atmospherethe atmosphere
Transmission BasicsTransmission Basics
Transmission has two meanings:Transmission has two meanings: Refers to process of issuing data signals on a Refers to process of issuing data signals on a
mediummedium Refers to progress of data signals over a Refers to progress of data signals over a
mediummedium
On a data network, information can be On a data network, information can be transmitted via one of two methods:transmitted via one of two methods: AnalogAnalog DigitalDigital
Transmission BasicsTransmission Basics
Both analog and digital signals are generated Both analog and digital signals are generated by electrical current, pressure of which is by electrical current, pressure of which is measured in measured in voltsvolts
In analog signals, voltage varies continuouslyIn analog signals, voltage varies continuously
In digital signals, voltage turns off and on In digital signals, voltage turns off and on repeatedlyrepeatedly
Transmission BasicsTransmission Basics
Figure 4-1: Example of an analog signal
Transmission BasicsTransmission Basics
AmplitudeAmplitude Measure of a signal’s strengthMeasure of a signal’s strength
FrequencyFrequency Number of times a signal’s amplitude changes Number of times a signal’s amplitude changes
over a period of timeover a period of time Expressed in Expressed in hhertz (Hz)ertz (Hz)
WavelengthWavelength Distances between corresponding points on a Distances between corresponding points on a
wave’s cyclewave’s cycle
Transmission BasicsTransmission Basics
PhasePhase Refers to progress of a wave over time in relationship to a fixed pointRefers to progress of a wave over time in relationship to a fixed point
Figure 4-2: Phase differences
Transmission BasicsTransmission Basics
Figure 4-3: A complex analog signal representing human speech
Transmission BasicsTransmission Basics
BinaryBinary system encodes using 1s and 0s system encodes using 1s and 0s
BitsBits can only have a value of either 1 or 0 can only have a value of either 1 or 0
Eight bits together form a Eight bits together form a bytebyte
NoiseNoise or any interference that may degrade or any interference that may degrade signals affects digital signals less than analog signals affects digital signals less than analog signalssignals
Transmission BasicsTransmission Basics
Figure 4-4: Example of a digital signal
Data ModulationData Modulation
ModemModem Name reflects function as modulator/demodulatorName reflects function as modulator/demodulator
ModulationModulation Technique for formatting signalsTechnique for formatting signals
Frequency modulation (FM)Frequency modulation (FM) Method of data modulation in which frequency of Method of data modulation in which frequency of
carrier signal is modified by application of a data signalcarrier signal is modified by application of a data signal
Amplitude modulation (AM)Amplitude modulation (AM) Modulation technique in which amplitude of carrier Modulation technique in which amplitude of carrier
signal is modified by application of a data signalsignal is modified by application of a data signal
Data ModulationData Modulation
Figure 4-5: A carrier wave modified by frequency modulation
Transmission DirectionTransmission Direction
SimplexSimplex Signals travel in only one directionSignals travel in only one direction
Half-duplexHalf-duplex Signals may travel in both directions over a Signals may travel in both directions over a
medium but in only one direction at a timemedium but in only one direction at a time
Full-duplexFull-duplex Signals are free to travel in both directions Signals are free to travel in both directions
over a medium simultaneouslyover a medium simultaneously Also referred to just as Also referred to just as duplexduplex
Transmission DirectionTransmission Direction
ChannelChannel Distinct communication path between two or more nodesDistinct communication path between two or more nodes
Figure 4-6: Simplex, half-duplex, and full-duplex transmission
Transmission DirectionTransmission Direction
MultiplexingMultiplexing Allows multiple signals to travel simultaneously Allows multiple signals to travel simultaneously
over one mediumover one medium To accommodate multiple signals, single medium To accommodate multiple signals, single medium
is logically separated into is logically separated into subchannelssubchannels For each type of multiplexing:For each type of multiplexing:
Multiplexer (mux)Multiplexer (mux) is required at sending end of is required at sending end of channelchannel
Demultiplexer (demux)Demultiplexer (demux) separates the combined separates the combined signals and regenerates them in original formsignals and regenerates them in original form
Transmission DirectionTransmission Direction
Time division multiplexing (TDM)Time division multiplexing (TDM) Divides channel into multiple intervals of timeDivides channel into multiple intervals of time
Figure 4-7: Time division multiplexing
Transmission DirectionTransmission Direction
Wavelength division multiplexing (WDM)Wavelength division multiplexing (WDM) Used only with fiber-optic cableUsed only with fiber-optic cable Data is transmitted as pulses of lightData is transmitted as pulses of light Fiber-optic modem (FOM)Fiber-optic modem (FOM) is a demultiplexer used on fiber is a demultiplexer used on fiber
networks that employ WDMnetworks that employ WDM
Figure 4-9: Wavelength division multiplexing
Relationships Between NodesRelationships Between Nodes
Point-to-pointPoint-to-point Transmission involving one transmitter and Transmission involving one transmitter and
one receiverone receiver
BroadcastBroadcast Transmission involving one transmitter and Transmission involving one transmitter and
multiple receiversmultiple receivers
WebcastingWebcasting Broadcast transmission used over the WebBroadcast transmission used over the Web
Relationships Between NodesRelationships Between Nodes
Figure 4-10: Point-to-point versus broadcast transmission
Throughput and BandwidthThroughput and Bandwidth
ThroughputThroughput is amount of data the medium is amount of data the medium can transmit during a given period of timecan transmit during a given period of time Also called Also called capacitycapacity
BandwidthBandwidth measures difference between measures difference between highest and lowest frequencies a media can highest and lowest frequencies a media can transmittransmit Range of frequencies is directly related to Range of frequencies is directly related to
throughputthroughput
Transmission FlawsTransmission Flaws
Electromagnetic interference (EMI)Electromagnetic interference (EMI) Interference that may be caused by motors, Interference that may be caused by motors,
power lines, television, copiers, fluorescent lights, power lines, television, copiers, fluorescent lights, or other sources of electrical activityor other sources of electrical activity
Radiofrequency interference (RFI)Radiofrequency interference (RFI) Interference that may be generated by motors, Interference that may be generated by motors,
power lines, televisions, copiers, fluorescent power lines, televisions, copiers, fluorescent lights, or broadcast signals from radio or TV lights, or broadcast signals from radio or TV towerstowers
Transmission FlawsTransmission Flaws
Figure 4-11: An analog signal distorted by noise
Transmission FlawsTransmission Flaws
Figure 4-12: A digital signal distorted by noise
Transmission FlawsTransmission Flaws
AttenuationAttenuation Loss of signal strength as transmission travels away from sourceLoss of signal strength as transmission travels away from source Analog signals pass through an Analog signals pass through an amplifieramplifier, which increases not , which increases not
only voltage of a signal but also noise accumulatedonly voltage of a signal but also noise accumulated
Figure 4-13: An analog signal distorted by noise, and then amplified
Transmission FlawsTransmission Flaws
RegenerationRegeneration Process of retransmitting a digital signalProcess of retransmitting a digital signal
RepeaterRepeater Device used to regenerate a signalDevice used to regenerate a signal
Figure 4-14: A digital signal distorted by noise, and then repeated
Coaxial CableCoaxial Cable
Consists of Consists of central central copper core copper core surrounded surrounded by an by an insulator, insulator, braidingbraiding, , and outer and outer cover called cover called a a sheathsheath
Figure 4-15: Coaxial cable
Coaxial CableCoaxial Cable
Table 4-2: Some types of coaxial cable
Thicknet (10Base5)Thicknet (10Base5)
Also called Also called thickwire Ethernetthickwire EthernetRigid coaxial cable used on original Ethernet Rigid coaxial cable used on original Ethernet networksnetworks
IEEE designates Thicknet as IEEE designates Thicknet as 10Base510Base5 EthernetEthernetAlmost never used on new networks but you Almost never used on new networks but you may find it on older networksmay find it on older networks Used to connect one data closet to another as Used to connect one data closet to another as
part of network part of network backbonebackbone
Thicknet CharacteristicsThicknet Characteristics
ThroughputThroughput According to IEEE 802.3, Thicknet transmits According to IEEE 802.3, Thicknet transmits
data at maximum rate of 10 Mbpsdata at maximum rate of 10 Mbps
CostCost Less expensive than fiber-optic but more Less expensive than fiber-optic but more
expensive than some other types of coaxial expensive than some other types of coaxial cablecable
ConnectorConnector Can include a few different types of Can include a few different types of
connectors, which are very different from connectors, which are very different from those used on modern networksthose used on modern networks
Thicknet CharacteristicsThicknet Characteristics
N-series connector (or n connector)N-series connector (or n connector) Screw-and-barrel arrangement securely connects coaxial Screw-and-barrel arrangement securely connects coaxial
cable segments and devicescable segments and devices
Figure 4-18: N-Series connector
Thicknet CharacteristicsThicknet Characteristics
Noise immunityNoise immunity Because of its wide diameter and excellent Because of its wide diameter and excellent
shielding, has the highest resistance to noise shielding, has the highest resistance to noise of any commonly used types of network wiringof any commonly used types of network wiring
Size and scalabilitySize and scalability Because of its high noise resistance, it allows Because of its high noise resistance, it allows
data to travel longer than other types of data to travel longer than other types of cablingcabling
Thinnet (10Base2)Thinnet (10Base2)
Also known as Also known as thin Ethernetthin Ethernet
Characteristics:Characteristics: ThroughputThroughput
Can transmit at maximum rate of 10 MbpsCan transmit at maximum rate of 10 Mbps CostCost
Less expensive than Thicknet and fiber-optic cableLess expensive than Thicknet and fiber-optic cable
More expensive than twisted-pair wiringMore expensive than twisted-pair wiring ConnectorsConnectors
Connects wire to network devices with Connects wire to network devices with BNC T-connectorsBNC T-connectors
A seen in Figure 4-19, A seen in Figure 4-19, BNC barrel connectorsBNC barrel connectors are used are used to join two Thinnet cable segments togetherto join two Thinnet cable segments together
Thinnet (10Base2)Thinnet (10Base2)
Characteristics Characteristics (cont.):(cont.): Size and scalabilitySize and scalability
Allows a maximum Allows a maximum of 185 m per of 185 m per network segment network segment (see Figure 4-20)(see Figure 4-20)
Noise immunityNoise immunityMore resistant than More resistant than twisted-pair wiringtwisted-pair wiring
Less resistant than Less resistant than twisted-pair wiringtwisted-pair wiring Figure 4-19: Thinnet BNC connectors
Thinnet (10Base2)Thinnet (10Base2)
Signal bounceSignal bounce Caused by Caused by
improper improper termination on termination on a bus networka bus network
Travels Travels endlessly endlessly between two between two ends of ends of networknetwork
Prevents new Prevents new signals from signals from getting throughgetting through
Figure 4-20: A 10Base2 Ethernet network
Twisted-Pair (TP) CableTwisted-Pair (TP) CableColor-coded pairs of Color-coded pairs of insulated copper wires insulated copper wires twisted around each twisted around each other and encased in other and encased in plastic coatingplastic coating
Twists in wire help Twists in wire help reduce effects ofreduce effects of crosstalkcrosstalk
Number of twists per Number of twists per meter or foot known as meter or foot known as twist ratiotwist ratio
Alien CrosstalkAlien Crosstalk When signals from When signals from
adjacent cables interfere adjacent cables interfere with another cable’s with another cable’s transmissiontransmission
Figure 21: Twisted-pair cable
Shielded Twisted-Pair (STP)Shielded Twisted-Pair (STP)
STP cable consists of twisted wire pairs that are STP cable consists of twisted wire pairs that are individually insulated and surrounded by shielding individually insulated and surrounded by shielding made of metallic substancemade of metallic substance
Figure 4-22: STP cable
Unshielded Twisted-PairUnshielded Twisted-Pair
Consists of one or more insulated wire pairs Consists of one or more insulated wire pairs encased in a plastic sheathencased in a plastic sheathDoes not contain additional shieldingDoes not contain additional shielding
Figure 4-23: UTP cable
Unshielded Twisted-PairUnshielded Twisted-Pair
To manage To manage network cabling, it network cabling, it is necessary to be is necessary to be familiar with familiar with standards used on standards used on modern networks, modern networks, particularly particularly Category 3 (CAT3) Category 3 (CAT3) and Category 5 and Category 5 (CAT5)(CAT5)
Figure 4-24: A CAT5 UTP cable
Comparing STP and UTPComparing STP and UTP
ThroughputThroughput Both can transmit up to 100 MbpsBoth can transmit up to 100 Mbps
CostCost Typically, STP is more expensiveTypically, STP is more expensive
ConnectorConnector Both use Both use RJ-45RJ-45 connectors (see Figure 4-27) and data connectors (see Figure 4-27) and data
jacksjacks
Noise immunityNoise immunity STP is more noise-resistantSTP is more noise-resistant
Size and scalabilitySize and scalability Maximum segment length for both is 100 metersMaximum segment length for both is 100 meters
RJ-45 ConnectorRJ-45 Connector
Figure 4-27: An RJ-45 connector
Fiber-Optic CableFiber-Optic Cable
Contains one or Contains one or several glass several glass fibers at its fibers at its corecore Surrounding Surrounding
the fibers is a the fibers is a layer of glass layer of glass called called claddingcladding
Figure 4-28: A fiber-optic cable
Fiber-Optic CableFiber-Optic Cable
Single-mode Single-mode fiberfiber Carries light Carries light
pulses along pulses along single pathsingle path
Multimode fiberMultimode fiber Many pulses of Many pulses of
light generated light generated by LED travel at by LED travel at different anglesdifferent angles Figure 4-29: Single-mode and
multimode fiber-optic cables
Fiber-Optic CableFiber-Optic Cable
ThroughputThroughput Reliable in transmitting up to 1 gigabit per Reliable in transmitting up to 1 gigabit per
secondsecond
CostCost Most expensive type of cableMost expensive type of cable
Fiber-Optic CableFiber-Optic Cable
Noise immunityNoise immunity Unaffected by either EMI or RFIUnaffected by either EMI or RFI
Size and scalabilitySize and scalability Network segments made from fiber can span Network segments made from fiber can span
100 meters100 meters Signals transmitted over fiber can experience Signals transmitted over fiber can experience
optical lossoptical loss
Fiber-Optic CableFiber-Optic Cable
Two popular connectors used with fiber-optic cable:Two popular connectors used with fiber-optic cable: ST connectorsST connectors SC connectorsSC connectors
Figure 4-30: ST and SC fiber connectors
Atmospheric Transmission MediaAtmospheric Transmission Media
Infrared transmissionInfrared transmission InfraredInfrared networks use infrared light networks use infrared light
signals to transmit data through spacesignals to transmit data through space Direct infrared transmissionDirect infrared transmission depends depends
on transmitter and receiver remaining on transmitter and receiver remaining within line of sightwithin line of sight
In In indirect infrared transmissionindirect infrared transmission, , signals can bounce off of walls, ceilings, signals can bounce off of walls, ceilings, and any other objects in their pathand any other objects in their path
Atmospheric Transmission MediaAtmospheric Transmission Media
RF transmissionRF transmission Radio frequency (RF)Radio frequency (RF) transmission relies transmission relies
on signals broadcast over specific frequencieson signals broadcast over specific frequencies Two most common RF technologies:Two most common RF technologies:
NarrowbandNarrowband
Spread spectrumSpread spectrum
Choosing the Right Transmission Choosing the Right Transmission MediaMedia
Areas of high EMI or RFIAreas of high EMI or RFI
Corners and small spacesCorners and small spaces
DistanceDistance
SecuritySecurity
Existing infrastructureExisting infrastructure
GrowthGrowth
Chapter SummaryChapter Summary
Information can be transmitted via analog or digital Information can be transmitted via analog or digital methodologymethodology
Throughput is the amount of data a medium can Throughput is the amount of data a medium can transmit during a given period of timetransmit during a given period of time
Noise is interference that distorts an analog or Noise is interference that distorts an analog or digital signaldigital signal
Costs depend on many factorsCosts depend on many factors
There are three specifications that dictate size and There are three specifications that dictate size and scalability of networking mediascalability of networking media
Connectors connect wire to the network deviceConnectors connect wire to the network device
Chapter SummaryChapter Summary
Coaxial cable consists of central copper core Coaxial cable consists of central copper core surrounded by an insulator and a sheathsurrounded by an insulator and a sheathThicknet cabling is a rigid coaxial cable used Thicknet cabling is a rigid coaxial cable used for original Ethernet networksfor original Ethernet networksBoth Thicknet and Thinnet coaxial cable rely Both Thicknet and Thinnet coaxial cable rely on bus topology and must be terminated at on bus topology and must be terminated at both ends with a resistorboth ends with a resistorTwisted-pair cable consists of color-coded Twisted-pair cable consists of color-coded pairs of insulated copper wires, twisted around pairs of insulated copper wires, twisted around each other and encased in plastic coatingeach other and encased in plastic coating
Chapter SummaryChapter Summary
STP cable consists of twisted pair wires STP cable consists of twisted pair wires individually insulated and surrounded by a individually insulated and surrounded by a shielding made of metallic substanceshielding made of metallic substance
UTP cabling consists of one or more insulated UTP cabling consists of one or more insulated wire pairs encased in a plastic sheathwire pairs encased in a plastic sheath
Fiber-optic cable contains one or several Fiber-optic cable contains one or several glass fibers in its coreglass fibers in its core
On today’s networks, fiber is used primarily as On today’s networks, fiber is used primarily as backbone cablebackbone cable