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Networking:MediaAccessControl
MestradoemEngenhariaInformáDcaedeComputadoresMasterDegree(MSc)inInformaDonSystemsandComputerEngineering
Administração e Gestão de Infra-estruturas de IT IT Infrastructure Management and Administration
TODAY
PhysicalLayer
Transmission
Media
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3
Let’sgoPhysical
ThePurposeofthePhysicalLayer:
Deliverthebits!
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TransmissionmodesatthePhysicalLayer:
Basebandtransmission:DigitalsignalssentasDirectCurrent(DC)Electricalpulses(copper) orLightpulses(fiber)
Broadbandtransmission:DigitalsignalsmodulatedinRadio-frequency(RF)analogwaves
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Digitalsignals:Pulsesofvoltages
High/PosiDvevoltagerepresentsalogical1
Low/Zerovoltagerepresentsalogical0
Digitalsignals:PulsesofLight
Lightrepresentsalogical1
Nolightrepresentsalogical0
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Transmission: Digital
Binarysystem:1sand0srepresentinformaDon
Modem:
AccomplishestranslaDon
Modulator/demodulator
Datamodula;on:
Technologymodifyinganalogsignals
MakedatasuitableforcarryingoveracommunicaDonpath
Carrierwave(HF-HighFrequency):
CombinedwithanotheranalogsignalproducesuniquesignaltransmiZedfromonenodetoanother
Purpose:ConveyinformaDon
Informa;onwave(LF-LowFrequency):
Addedtocarrierwave
Modifiesonecarrierwaveproperty
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Transmission: Modulation
Digitalmodula;on:
Carrierfrequencymodified
ByapplicaDonofdatasignal:
InAmplitude(AM)
InFrequency(FM)
InPhase(PM)
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Transmission: Modulation
TheelectricfieldofanelectromagneDcwavewithtwopolarisaDoncomponentsExandEy
ThecomplexmodulaDonschemeaddstotheamplitudeE,thephaseФofthewave(𝜙)modulatedfordefiningtheinformaDonsymbols
TheelectricfieldofthemodulatedwavecanbedescribedinthecomplexplanewithanI/Qdiagram,where,Iisthein-phase(realpart)andQthequadrature(imaginarypart)
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Transmission: Modulation
Simplex:
Signaltransmission:onedirecDon
Half-duplextransmission:
Signaltransmission:bothdirecDons,oneataDme
OnecommunicaDonchannel,sharedformulDplenodestoexchangeinformaDon
Full-duplex:
Signalstransmission:bothdirecDonssimultaneously
Usedondatanetworks
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Transmission: Simplex, Half-Duplex, DuplexChannel:DisDnctcommunicaDonpathbetweennodes,separatedphysicallyorlogically
MulDplesignals
Travelsimultaneouslyoveronemedium
Sub-channels:
LogicalmulDplesmallerchannels
Mul;plexer(mux):
Combinesmanychannelsignals
Demul;plexer(demux):
Separatescombinedsignals
Regeneratesthem
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Transmission: Multiplexing
TDM(DmedivisionmulDplexing):
DivideschannelintomulDpleDmeintervals
FDM(frequencydivisionmulDplexing)
UniquefrequencybandforeachcommunicaDonssubchannel
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Transmission: Multiplexing
Sta;s;calmul;plexing
TransmiZerassignsslotstonodes,accordingtopriorityorneed
WDM(wavelengthdivisionmulDplexing)
Onefiber-opDcconnecDoncarriesmulDplelightsignalssimultaneously
DWDM(densewavelengthdivisionmulDplexing)
Usedonmostmodernfiber-opDcnetworks
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Transmission: Multiplexing
Point-to-pointtransmission:
OnetransmiZerandonereceiver
Point-to-mul;pointtransmission:
OnetransmiZerandmulDplereceivers
Broadcasttransmission:
OnetransmiZerandmulDple,undefinedreceivers
Usedonwiredandwirelessnetworks
Non-broadcast
OnetransmiZerandmulDple,definedreceivers
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Transmission: Relationships Between Nodes
Noise:AnyundesirableinfluencedegradingordistorDngsignal
Typesofnoise:
EMF/EMR(electromagneDcField/RadiaDon)
EMI/RFI(radio-frequencyInterference)
Crosstalk:
NEXT(nearendcrosstalk)
PotenDalcause:improperterminaDon
Environmentalinfluences:Heat
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Transmission Flaws
EMFandEMR:
Electro-MagneDcFieldandElectro-MagneDcRadiaDon,generallydescribesthestrengthofamagneDcfieldanditsabilitytoinducecurrent.
EMIandRFI:
Electro-MagneDcInterferenceandRadioFrequencyInterferencedescribeundesired,inducedelectricalcurrent.RFIappliedtohigherfrequencies.
EMP:
Electro-MoDvePulsewhichisasuddenbutshort-livedincreaseinEMIorRFI.ObendestrucDve.EMPsourcesincludeelectricalstorms,solarstormsandweapons.
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Transmission Flaws
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Ananalogsignaldistortedbynoiseandthenamplified
Adigitalsignaldistortedbynoiseandthenrepeated
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Transmission Flaws
AYenua;on:
Lossofsignal’sstrengthasittravelsawayfromsource
Signalboos;ngtechnology:
Analogsignalspassthroughamplifier; noiseisalsoamplified
RegeneraDon:
DigitalsignalsretransmiZedinoriginalform
Repeater:deviceregeneraDngdigitalsignals
Latency:
DelaybetweensignaltransmissionandrecepDon
Causes:Cablelength,InterveningconnecDvitydevice
RTT(roundtripDme)
Timeforpackettogofromsendertoreceiver,thenbackfromreceivertosender
Measuredinmilliseconds
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Transmission Flaws
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NetworkMedia
PhysicalLayerStandards
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Standard Organization Networking Standards
ISO • ISO 8877: Officially adopted the RJ connectors (e.g., RJ-11, RJ-45) • ISO 11801: Network cabling standard similar to EIA/TIA 568.
EIA/TIA
• TIA-568-C: Telecommunications cabling standards, used by nearly all voice, video and data networks.
• TIA-569-B: Commercial Building Standards for Telecommunications Pathways and Spaces
• TIA-598-C: Fiber optic color coding • TIA-942: Telecommunications Infrastructure Standard for Data Centers
ANSI • 568-C: RJ-45 pinouts. Co-developed with EIA/TIA
ITU-T • G.992: ADSL
IEEE• 802.3: Ethernet • 802.11: Wireless LAN (WLAN) & Mesh (Wi-Fi certification) • 802.15: Bluetooth
PhysicalLayerFundamentalPrinciples
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Media Physical Components Frame Encoding Technique Signalling Method
Copper Cable
• UTP • Coaxial • Connectors • NICs • Ports • Interfaces
• Manchester Encoding • Non-Return to Zero (NRZ) techniques • 4B/5B codes are used with Multi-Level
Transition Level 3 (MLT-3) signaling • 8B/10B • PAM5
• Changes in the electromagnetic field
• Intensity of the electromagnetic field
• Phase of the electromagnetic wave
Fiber Optic Cable
• Single-mode Fiber • Multimode Fiber • Connectors • NICs • Interfaces • Lasers and LEDs • Photoreceptors
• Pulses of light • Wavelength multiplexing using different
colors
• A pulse equals 1. • No pulse is 0.
Wireless Media
• Access Points • NICs • Radio • Antennae
• DSSS (direct-sequence spread-spectrum) • OFDM (orthogonal frequency division
multiplexing)
• Radio waves
NetworkMedia:Copper
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ShieldedTwistedPair(STP)Cable
UnshieldedTwistedPair(UTP)
Cable
CoaxialCable
Color-codedinsulatedcopperwirepairs
0.4to0.8mmdiameter
EncasedinaplasDcsheath
Morewirepairtwistsperunitlength:
Moreresistancetocross-talk
Higher-quality
Moreexpensive
TwistraDo:Twistspermeterorfoot
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Network Media: Twisted-Pair Cable
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Network Media: Twisted-Pair Cable
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Network Media: Twisted-Pair Cable
UnshieldedTwistedPair(UTP) ScreenedTwistedPair(ScTP)
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Network Media: Twisted-Pair Cable
UnshieldedTwistedPair(UTP) ScreenedTwistedPair(ScTP)
Jacket
FoilShield
DrainWire
Filler
RipCord(notshown)
InsulatedTwistedPairConductors
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Network Media: Shielded Twisted-Pair (STP)
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Network Media: Shielded Twisted-Pair (STP)
Jacket
BraidedShield
FoilShield(IndividuallyShieldedPair)
ConductorPairs
UTP/STPCategoriesUTP/STPcableisclassifiedintoperformance-basedcategories.
ThespecificaDonsforthecategoriesaredefinedintheTIA/EIA568C,ISO11801andIEC61156standards.
Categoriesareaddedtoandremovedfromthestandardsastechnologychangesandimproves.
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Category Data Rate (Mbps) Comments
1 0.02 Telephone and Signal Wire2 4 Early Token Ring networks
3 10 10Mbps Ethernet, still frequently used for telephone-only installations (residential)
4 20 Latter Token Ring networks. Short-lived Category.5 100 100Mbps (fast) Ethernet, ATM. Not recommended.
5e 100 Improved performance over Cat 5. Recommended.
6 1000 Gigabit Ethernet. Recommended.
6a 10,000 Recommended for new installations but expensive and thicker.
7 ? In discussion and lab testing. Likely ScTP with individually shielded pairs or conductors.
UTPCablingStandards
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TypesofUTP/STPCablingTerminaDons
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TwistedPair:Connectors
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Future-TwistedPairCategory7:
1GHz(Cat6=250MHz,Cat6a=500MHz)Currentlyindiscussion.Requiresafundamentalcablestructuralchange(UTPhasachieveditslimitwithCat6/6a).Willneedanewconnector.Class‘F’inEurope.
Category8
Notdetermined.Likelyindividualshieldedtwistedpairwithanoverallshield
Changesthatmaytakeplace:
Shielding:Overall,individualpairsorindividualconductors;Mayhaveaseparatedrainwire
Distance:Maydecreasethemax.distances
Increasedwiregauge:Reducedresistance
Increasedsize:BeZerandthickerinsulaDon(dielectric);separatorbetweenpairs?
Differentconnectorstyle(TERA,GG45inEurope)
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Future-TwistedPair:Connectors
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TERA and GG45 connectors The TERA connector may be used for broadcast applications
The GG45 is backward compatible with the 8 position modular plug
Centralmetalcore(obencopper)surroundedbyinsulator
Braidedmetalshielding(braidingorshield)
Outercover(sheathorjacket)
Highnoiseresistance:carrysignalsfartherbeforeamplifierrequired
HundredsofspecificaDons:
RGspecificaDonnumber
Differences:shieldingandconducDngcores
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Network Media: Coaxial Cable
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Network Media: Coaxial Cable
F-typeconnector
BNCConnector
IBM3270:RG62Coax&BNCconnector(star)
IBMSystem3X:TwinaxCabling(daisy-chain)
Thicknet&ThinnetCoax(Ethernet)
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Network Media: Coaxial Cable
One(orseveral)glassorplasDcfibersatitscenter(core)
Datatransmission:
Pulsinglightsentfromlaser
LED(light-emitngdiode)throughcentralfibers
Cladding:
LayerofglassorplasDcsurroundingfibers
DifferentdensityfromglassorplasDcinstrands
Reflectslightbacktocoreandallowsfibertobend
Plas;cbuffer:Protectscladding
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Network Media: Fiber Optic Cable
Cladding:
LayerofglassorplasDcsurroundingfibers
DifferentdensityfromglassorplasDcinstrands
Reflectslightbacktocoreandallowsfibertobend
Plas;cbuffer:Protectscladding
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Network Media: Fiber Optic Cable
SMF(Single-ModeFiber):
Usesnarrowcore(<10micronsindiameter)
Lasergeneratedlighttravelsoveronepath
LiZlereflecDon
Lightdoesnotdisperse
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Network Media: Fiber Optic Cable
MMF(MulDmodeFiber):
Corecommonsize:62.5microns
LaserorLEDgeneratedlightpulsestravelatdifferentangles
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Network Media: Fiber Optic Cable
Throughput:
Reliabletransmissionrates
Canreach100gigabits(or100,000megabits)persecondperchannel
Noiseimmunity:
UnaffectedbyEMI
Sizeandscalability:
550mto70km(1,510nmlaser)
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Network Media: Fiber Optic Cable
Connector:
ST(straightterminus)
SC(subscriberconnector)
LC(lightwaveconnector)
FC(fiberconnector)
MT-RJ(mechanicaltransferregisteredjack)
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Network Media: Fiber Optic Cable
FiberversusCopper
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Implementation Issues Copper Media Fibre OpticBandwidth Supported 10 Mbps – 10 Gbps 10 Mbps – 100 Gbps
Distance Relatively short (1 – 100 meters)
Relatively High (1 – 100,000 meters)
Immunity To EMI And RFI Low High (Completely immune)
Immunity To Electrical Hazards Low High (Completely immune)
Media And Connector Costs Lowest HighestInstallation Skills Required Lowest Highest
Safety Precautions Lowest Highest
CableMarkingsManufacturer
ModelNumber
DescripDon(shortform):#pairsorconductors;ConductorcharacterisDcs;Typeofcable(maybeanindustrynumber)
Manufacturingdate
Meterlengthmarking
Codecompliance
47Presenta;onnamegoeshere
Optical Cable markings for fire ratings. The markings include terms such as OFNR & Riser, OFN & FT-4, and OFNP & Plenum.
WirelessMediaWirelessdoeshavesomeareasofconcern,including:
Coveragearea
Interference
Security
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TypesofWirelessMedia
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• IEEE 802.11 standards, Commonly referred to as Wi-Fi. • Uses CSMA/CA • Variations include: • 802.11a: 54 Mbps, 5 GHz • 802.11b: 11 Mbps, 2.4 GHz • 802.11g: 54 Mbps, 2.4 GHz • 802.11n: 600 Mbps, 2.4 and 5 GHz • 802.11ac: 1 Gbps, 5 GHz • 802.11ad: 7 Gbps, 2.4 GHz, 5 GHz, and 60 GHz
• IEEE 802.15 standard • Supports speeds up to 3 Mb/s • Provides device pairing over distances from 1 to 100 meters.
• IEEE 802.16 standard • Provides speeds up to 1 Gbps • Uses a point-to-multipoint topology to provide wireless
broadband access.
IEEE802.11Wi-FiStandards
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Standard Maximum Speed Frequency Backwards
Compatible
802.11a 54 Mbps 5 GHz No
802.11b 11 Mbps 2.4 GHz No
802.11g 54 Mbps 2.4 GHz 802.11b
802.11n 600 Mbps 2.4 GHz or 5 GHz 802.11b/g
802.11ac 1.3 Gbps (1300 Mbps)
2.4 GHz and 5.5 GHz 802.11b/g/n
802.11ad 7 Gbps (7000 Mbps)
2.4 GHz, 5 GHz and 60 GHz 802.11b/g/n/ac
hZps://www.ted.com/talks/andrew_blum_what_is_the_internet_really
PhysicalLayer
Transmission
Media
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SUMMARY
AnyQuesDons? 53
