信息通信与网络技术基础总结解析.docx
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信息通信与网络技术基础总结解析.docx
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信息通信与网络技术基础总结解析
1.Datacommunicationistheexchangeofdatabetweendevicesviasomeformoftransmission
medium.
2.Datacommunicationsystemcomponentsaremessage,sender,receiver,mediumandprotocol.Protocolisasetofrulesthatgoverndatacommunication
Messageistheinformation(datatobecommunicated.
Senderisthedevicethatsendsthedatamessage.
Receiveristhedevicethatreceivesthemessage
Mediumisthephysicalpathbywhichamessagetravelsfromsendertoreceiver
3.Anetworkisasetofdevices(oftenreferredtoasnodesconnectedbymedialinks
4.Reliability:
frequencyoffailure
recoverytimeafterafailure
catastrophe
5.Aprotocolisasetofrulesthatgoverndatacommunication.
thekeyelementsofaprotocolare:
syntax
semantics
timing
6.Standards:
Defacto/byfact
Dejure/bylaw
7.ISO:
TheInternationalStandardsOrganization
ITU-T:
TheInternationalTelecommunicationUnion-TelecommunicationStandardsSector
ANSI:
TheAmericanNationalStandardsInstitute
IEEE:
TheInstituteofElectricalandElectronicsEngineers
EIA:
TheElectronicsIndustriesAssociation
8.Lineconfiguration:
Point-to-point:
wiredorwireless
Multipoint
9.Topology:
MeshStarBusTreeRing
Peer-to-peer:
Thedevicessharethelinkequally
Primary-Secondary:
Whereonedevicecontrolstrafficandtheothermusttransmitthrough
it
Peer-to-peer:
MeshRingBus
Primary-Secondary:
StarTreeBus
10.TransmissionMode:
SimplexHalf-duplexFull-duplex
Simplexmode:
onestationcantransmit,theothercanonlyreceive
Half-duplexmode:
Eachstationcanbothtransmitandreceive,butnotatthesametime.
Full-duplexmode:
Bothstationscantransmitandreceivesimultaneously
11.TheOpenSystemInterconnection(OSImodelisalayeredframeworkforthedesignofnetwork
systemthatallowsforcommunicationacrossalltypesofcomputersystems.
OSImodelhas7layers:
PhysicalDatalinkNetworkTransportationSessionPresentationApplication
12.Peertopeerprocesses:
Theprocessesoneachmachinethatcommunicateatagivenlayerare
calledpeer-to-peerprocesses.
Thiscommunicationisgovernedbyanagree-uponseriesofrulesandconventionscallprotocols
The7layersaredividedinto3groups:
thenetworksupportlayers(1,2,3
usersupportlayers(5,6,7
linktheabovesubgroups(4
13.fig.3.3
Theprocessstartsfromlayer7,thenmovefromlayertolayerindescendingsequentialorder,
ateachlayer(except7and1aheaderisadded.Atlayer2atrailerisaddedaswell.
14.Physicallayers:
Lineconfiguration
Datatransmissionmode
Topology
Signals
Encoding
Interface
Medium
15.ThePhysicallayercoordinatesthehardwareandsoftwarefunctionsrequiredtotransmitabit
streamoveraPhysicalmedium.
Itdealswithamechanicalandelectricalspecificationsoftheprimaryconnections
Thedatalinklayerisresponsiblefordeliveringframesfromonestationtothenextwithout
errors.
Itprovideserrorhandlingandflowcontrolbetweenonestationandthenext.
Thenetworklayerisresponsibleforthesource-to-destinationdeliveryofadatapacket.
Ithandlesswitchingandrouting
Thetransportlayerisresponsibleforthesource-to-destination(end-to-enddeliveryofthe
entiremessagefromoneapplicationtoanother.
Thesessionlayeristhenetworkdialogcontroller.
Itestablishes,maintains,andsynchronizestheinteractionbetweencommunicatingdevices.
Thepresentationlayerensuresinteroperabilityamongcommunicatingdevices.
Totransact,encrypt,andcompressdata
Theapplicationlayerenablestheuser,whetherhumanorsoftware,toaccessthenetwork.16.
HzkHz(10^3HzMHz(10^6HzGHz(10^9HzTHz(10^12Hz
sms(10^-3sus(10^-6sns(10^-9sps(10^-12s
17.ThefrequencySpectrumofasignalisthecombinationofallsinewavesignalsthatmakethat
signal.
Bandwidthofasignalisthewidthofthefrequencyspectrum.
18.Ifwesendonlythosecomponentswhoseamplitudesaresignificant(aboveanacceptable
threshold,wecanstillrecreatethedigitalsignalwithreasonableaccuracyatthe
receiver(minimumdistortion.Wecallthispartoftheinfinitespectrumthesignificantspectrum,anditsbandwidththesignificantbandwidth.
19.Channelcapacityisthemaximumbitrateatransmissionmediumcantransfer.
Itdependson:
thetypeofencodingtechnique,andthesignal-to-noiseratioofthesystem.
20.Encode:
Analog/DigitalD/DD/AA/A4kinds
D/Dencoding:
UnipolarBipolarPolar
Polar:
Non-ReturntoZero,levelNRZ-L:
0"-"1"+"
Non-ReturntoZero,InverseNRZ-I:
0"notchanged"1"convert"
ReturntoZeroRZ:
0"-to0"1"+to0"
Manchester0"+to-"1"-to+"
DifferentManchester0"transmission"1"notransmission"
Bipolar:
AMIB8ZSHDB3
21.PCMfourprocesses:
PAMquantizationbinaryencodingdigitalencoding
22.A/D
PAM:
PulseAmplitudeModulation
PCM:
PulsecodeModulatio
23.Nyquist采样定理:
f>=2f_max
24.D/Aencoding:
ASKFSKPSKQAM
25.Bitrate(比特率isthenumberofbitspersecond(bps
Baudrate(波特率isthenumberofsignalunitspersecond.
ASKbaudrate=bitrate=bandwidth(带宽
FSKbandwidth=fc1-fc0+Nbaud(波特率
26.Adiagramcalledconstellationorphase-statediagramisusedtoshowtherelationship
betweenphaseinPSK
27.Datatransmission:
ParallelSerial(AsynchronousSynchronous
28.Paralleltransmission:
usenwirestosendnbitsatonetime.
InSerialtransmission:
onebitfollowsanother,soweneedonlyonecommunicationchannelratherthannInAsynchronoustransmissionmode:
startbit(0stopbit(1gaps
InSynchronoustransmissionmode:
wesendbitsoneafteranotherwithoutstart/stopbitorgaps.
Itisresponsibilityofthereceivertogroupthebitsintomeaningfulframes.
29.ADTEisanydevicethatisasourceofordestinationforbinarydigitaldata.
ADCEisanydevicethattransmitsorreceivesdataintheformofananalogordigitalthrougha
network.
DTE-DCEstandardstrytodefinethemechanical,electricalandfunctionalcharacteristicsofconnectionbetweentheDTEandDCE.
30.EIA-530standardisaversionofEIA-449thatusesDB-25Pins.
31.ModemisthemostfamiliartypeofDCE.
Modemstandsformodulator/demodulator.
Amodulatorconvertsadigitalsignaltoananalogsignal.
Ademodulatorconvertsananalogsignaltoadigitalsignal.
32.Intelligentmodemcontainsoftwaretosupportanumberofadditionalfunctions,suchas
automaticansweringanddialing.
33.Transmissionmedia:
GuidedmediaUnguidedmedia
Guidedmedia:
twisted-paircable,coaxialcablefiber-opticcable
UTP:
UnshieldedTwisted-pair
STP:
ShieldedTwisted-pair
34.Propagationmode:
MultimodeSinglemode
Multimode:
Step-indexGraded-index
35.光纤优点:
noiseresistance,lesssignalattenuation,higherbandwidth
缺点:
costmuch,hardtoinstallate/maintain,fragilityeasybrokenthanwire
36.Multiplexingisthesetoftechniquesthatallowsthesimultaneoustransmissionofmultiple
signalsacrossasingledatalink
APathreferstoaphysicallink.
Channelreferstoaportionofapaththatcarriesatransmissionbetweenagivenpairofdevices.
Multiplexing:
Frequency-divisionmultiplexing(FDM
Time-divisionmultiplexing(TDM
TDM:
overlapping.Definition:
SynchronousAsynchronous37.InFDM,channelsmustbeseparatedbytripsofunusedbandwidthtopreventsignalsfromFDMisananalogtechniquethatcanbeappliedwhenthebandwidthofalinkisgreaterthanthecombinedbandwidthofthesignal.TDMisadigitalprocessthatcanbeappliedwhenthedataratecapacityofthetransmissionmediumisgreaterthanthedataraterequiredbythesendingandreceivingdevices.38.Errors:
Single-bit-error,Multiple-biterror,burst-errorErrordetectionandcorrectionisdonebythedatalinklayerortransportlayer.Single-biterrorsiswhenonlyonebitinthedataunithaschanged.Multiple-biterroriswhentwoormorenonconsecutivebitsinthedataunithavechanged.Bursterrormeansthattwoormoreconsecutivebitsinthedataunithavechanged.39.Redundancymeansaddingextrabitsfordetectingerrorsatthedestination.Redundancycheck(冗余校验:
VRC,VRC:
LRC:
CRC:
LRC,CRC,checksumVerticalRedundancyCheck(垂直冗余校验LongitudinalRedundancyCheck(纵向冗余校验CyclicalRedundancyCheck(循环冗余校验usedindatalinklayerVRC,LRC,CRCisimplementedinphysicallayer,transportlayer.1.Checksumisprimarilyusedbynetworks,includingtheinternet,andisimplementedintheInVRCaparitybitisaddedtoeverydataunitsothatthetotalnumberof1s(includingParitybitbecomesevenforeven-paritycheckoroddforodd-paritycheck.VRCcandetectallsingle-biterrors.Itcandetectmultiplebitorbursterrorsonlyifthetotalnumberoferrorsisodd.2.InLRC,aredundantunitisaddedafteranumberofdataunits.3.InCRCasequenceofbits,calledtheCRCortheCRCremainderisappendedtotheendofadataunit,sothattheresultingdataunitbecomesexactlydivisiblebyasecond,predeterminedbinarynumber.40.ApplicationPresentationSessionTransportNetworkDatalink:
PhysicalLinediscipline:
Whoshouldsendnow?
Flowcontrol:
Howmuchdatamaybesent?
LinedisciplineFlowcontrolErrorcontrol
Errorcontrol:
41.Linediscipline:
Howcanerrorsbecorrected?
ENQ/ACKPoll/SelectEnquiry/acknowledgement:
ENQ/ACK.isusedinpeertopeercommunication,wheretherearededicatedlinkbetweentwodevicesPoll/Selectlinedisciplineisusedinprimary-secondarycommunicationiftheprimarywantstoreceivedata,itasksthesecondariesIftheyhaveanythingtosend;thisfunctioniscalledpolling.Iftheprimarywantstoreceive,thisfunctioniscalledselecting.43.Flowcontrol:
stop-and-waitARQgo-back-nSlidingwindowARQselective-rejectslidingwindowARQ:
Ingo-back-nARQ,retrainsmissionbeginswiththelastunacknowledgedframeevenifsubseque
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