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1CHAPTER1IntroductionSolutionstoReviewQuestionsandExercisesReviewQuestions1.Thefivecomponentsofadatacommunicationsystemarethesender,receiver,transmissionmedium,message,andprotocol.2.Theadvantagesofdistributedprocessingaresecurity,accesstodistributeddata-bases,collaborativeprocessing,andfasterproblemsolving.3.Thethreecriteriaareperformance,reliability,andsecurity.4.Advantagesofamultipointoverapoint-to-pointconfiguration(typeofconnec-tion)includeeaseofinstallationandlowcost.5.Lineconfigurations(ortypesofconnections)arepoint-to-pointandmultipoint.6.Wecandividelineconfigurationintwobroadcategories:a.Point-to-point:mesh,star,andring.b.Multipoint:bus7.Inhalf-duplextransmission,onlyoneentitycansendatatime;inafull-duplextransmission,bothentitiescansendatthesametime.8.Wegiveanadvantageforeachoffournetworktopologies:a.Mesh:secureb.Bus:easyinstallationc.Star:robustd.Ring:easyfaultisolation9.Thenumberofcablesforeachtypeofnetworkis:a.Mesh:n(n–1)/2b.Star:nc.Ring:n–1d.Bus:onebackboneandndroplines10.Thegeneralfactorsaresize,distances(coveredbythenetwork),structure,andownership.Page1JUNE_CSE09_JSTU211.Aninternetisaninterconnectionofnetworks.TheInternetisthenameofaspe-cificworldwidenetwork12.Aprotocoldefineswhatiscommunicated,inwhatwayandwhen.Thisprovidesaccurateandtimelytransferofinformationbetweendifferentdevicesonanet-work.13.Standardsareneededtocreateandmaintainanopenandcompetitivemarketformanufacturers,tocoordinateprotocolrules,andthusguaranteecompatibilityofdatacommunicationtechnologies.Exercises14.Unicodeuses32bitstorepresentasymboloracharacter.Wecandefine232differ-entsymbolsorcharacters.15.With16bits,wecanrepresentupto216differentcolors.16.a.Cablelinks:n(n–1)/2=(6×5)/2=15b.Numberofports:(n–1)=5portsneededperdevice17.a.Meshtopology:Ifoneconnectionfails,theotherconnectionswillstillbework-ing.b.Startopology:Theotherdeviceswillstillbeabletosenddatathroughthehub;therewillbenoaccesstothedevicewhichhasthefailedconnectiontothehub.c.BusTopology:Alltransmissionstopsifthefailureisinthebus.Ifthedrop-linefails,onlythecorrespondingdevicecannotoperate.d.RingTopology:Thefailedconnectionmaydisablethewholenetworkunlessitisadualringorthereisaby-passmechanism.18.ThisisaLAN.TheEthernethubcreatesaLANaswewillseeinChapter13.19.Theoretically,inaringtopology,unpluggingonestation,interruptsthering.How-ever,mostringnetworksuseamechanismthatbypassesthestation;theringcancontinueitsoperation.20.Inabustopology,nostationisinthepathofthesignal.Unpluggingastationhasnoeffectontheoperationoftherestofthenetwork.21.SeeFigure1.122.SeeFigure1.2.23.a.E-mailisnotaninteractiveapplication.Evenifitisdeliveredimmediately,itmaystayinthemail-boxofthereceiverforawhile.Itisnotsensitivetodelay.b.Wenormallydonotexpectafiletobecopiedimmediately.Itisnotverysensi-tivetodelay.c.SurfingtheInternetistheanapplicationverysensitivetodelay.Weexcepttogetaccesstothesitewearesearching.24.Inthiscase,thecommunicationisonlybetweenacallerandthecallee.Adedi-catedlineisestablishedbetweenthem.Theconnectionispoint-to-point.Page2JUNE_CSE09_JSTU325.Thetelephonenetworkwasoriginallydesignedforvoicecommunication;theInternetwasoriginallydesignedfordatacommunication.Thetwonetworksaresimilarinthefactthatbotharemadeofinterconnectionsofsmallnetworks.Thetelephonenetwork,aswewillseeinfuturechapters,ismostlyacircuit-switchednetwork;theInternetismostlyapacket-switchednetwork.Figure1.1SolutiontoExercise21Figure1.2SolutiontoExercise22StationStationStationRepeaterStationStationStationRepeaterStationStationStationRepeaterHubStationStationStationStationRepeaterRepeaterPage3JUNE_CSE09_JSTU4Page4JUNE_CSE09_JSTU1CHAPTER2NetworkModelsSolutionstoReviewQuestionsandExercisesReviewQuestions1.TheInternetmodel,asdiscussedinthischapter,includephysical,datalink,net-work,transport,andapplicationlayers.2.Thenetworksupportlayersarethephysical,datalink,andnetworklayers.3.Theapplicationlayersupportstheuser.4.Thetransportlayerisresponsibleforprocess-to-processdeliveryoftheentiremessage,whereasthenetworklayeroverseeshost-to-hostdeliveryofindividualpackets.5.Peer-to-peerprocessesareprocessesontwoormoredevicescommunicatingatasamelayer6.Eachlayercallsupontheservicesofthelayerjustbelowitusinginterfacesbetweeneachpairofadjacentlayers.7.Headersandtrailersarecontroldataaddedatthebeginningandtheendofeachdataunitateachlayerofthesenderandremovedatthecorrespondinglayersofthereceiver.Theyprovidesourceanddestinationaddresses,synchronizationpoints,informationforerrordetection,etc.8.Thephysicallayerisresponsiblefortransmittingabitstreamoveraphysicalmedium.Itisconcernedwitha.physicalcharacteristicsofthemediab.representationofbitsc.typeofencodingd.synchronizationofbitse.transmissionrateandmodef.thewaydevicesareconnectedwitheachotherandtothelinks9.Thedatalinklayerisresponsiblefora.framingdatabitsb.providingthephysicaladdressesofthesender/receiverc.dataratecontrolSol-02.fmPage1Saturday,January21,200610:27AMPage5JUNE_CSE09_JSTU2d.detectionandcorrectionofdamagedandlostframes10.Thenetworklayerisconcernedwithdeliveryofapacketacrossmultiplenet-works;