中樞神經(jīng)系統(tǒng)結(jié)構(gòu)設(shè)計(jì),骨干

StructuredBackboneDesignofCNs

HabibYoussef,Ph.DDepartmentofComputerEngineeringKingFahdUniversityofPetroleum&MineralsDhahran,SaudiArabiaComputerNetworks第一頁(yè)，共一百五十一頁(yè)。Outline1.EnterpriseBackboneBasics2.StructuredCabling3.TypesofBackbones4.BackboneExamples5.TheNetworkDevelopmentLifeCycle(NDLC)第二頁(yè)，共一百五十一頁(yè)。EnterpriseBackboneBasicsModernorganizationshaveLargenetworksComplexcommunicationrequirementsAccesstomainframedataInternetworkingofseveralLANsConnectivitytoaWAN(theInternet)Transmissionofdataandnon-data第三頁(yè)，共一百五十一頁(yè)。BackboneBasics(Cont.)Complexrequirementsmandatedthestructuringofenterprise-wideinformationdistribution.SuchstructuringiseffectivelyachievedthroughasystemcalledBackbone.StructuredwiringcombinedwithBackbonesolutionprovideapowerfulandefficientnetworkingsolutiontocompany-widecommunicationneeds.第四頁(yè)，共一百五十一頁(yè)。BackboneBasics(Cont.)KeyFactorsinassessingnetworktopologies:PerformanceHighestnetworkavailability.Lowestlatency.Mostappropriateconnectivityforusers.ScalabilityAbilitytoexpandthenetworkintermsofend-pointsandaggregatebandwidthwithoutaffectingexistingusers.第五頁(yè)，共一百五十一頁(yè)。BackboneBasics(Cont.)Costofadministration:Theinherenteaseofmoves,adds,andchanges,plusthecapabilitytoefficientlydiagnose,remedy,orpreventnetworkoutages.StructuredBackbonesolutionsofferFlexibilityScalabilityTroubleshooting&ManageabilityPerformance第六頁(yè)，共一百五十一頁(yè)。StructuredCablingCablingplanshouldbeeasyto:implement,andaccommodatesfuturegrowth.Twostandardshavebeenissuedthatspecifycablingtypesandlayoutforstructuredcommercialbuildingswiring.Anetworkshouldfollowacablingplan:SelectionofcabletypesCablelayouttopology第七頁(yè)，共一百五十一頁(yè)。StructuredCablingStandardsEIA/TIA-568:IssuedjointlybytheElectronicIndustriesAssociationandtheTelecommunicationsIndustryAssoc.ISO11801:IssuedbytheInternationalOrganizationforStandardization.BothStandardsaresimilar.第八頁(yè)，共一百五十一頁(yè)。StructuredCabling(Cont.)Itisagenericwiringschemewiththefollowingcharacteristics:Wiringwithinacommercialbuilding.Cablingtosupportallformsofinformationtransfer.Cableselectionandlayoutisindependentofvendorandend-userequipment.Cablelayoutdesignedtoencompassdistributiontoallworkareaswithinthebuilding(relocationwouldn’tneedrewiring).第九頁(yè)，共一百五十一頁(yè)。StructuredCabling(Cont.)Basedontheuseofahierarchicalstar-wiredcablelayout.ExternalcablesterminateatEquipmentRoom(ER).Patchpanelandcross-connecthardwareconnectERtoInternalDistributionCable.Typically,firstlevelofdistributionconsistsofBackbonecables.Backbonecable(s)runfromERtoTelecomClosets(WiringClosets)oneachfloor.第十頁(yè)，共一百五十一頁(yè)。StructuredCabling(Cont.)WiringClosetcontainscross-connectequipmentforinterconnectingcableonasinglefloortotheBackbone.CabledistributedonasingleflooriscalledHorizontalCabling,andconnectstheBackbonetoWallOutletsthatserviceindividualtelephoneanddataequipment.第十一頁(yè)，共一百五十一頁(yè)。StructuredCabling(Cont.)Basedontheuseofahierarchicalstar-wiredcablelayout.ExternalCableTelecom.ClosetEquipmentRoomBackboneHorizontalCableWorkArea第十二頁(yè)，共一百五十一頁(yè)。StructuredCablingTerminologyBackbone Afacilitybetweentelecommunicationsclosetsorfloordistributionterminals,theentrancefacilities,andtheequipmentroomswithinorbetweenbuildingsHorizontalCabling Thewiring/cablingbetweenthetelecom outletandthehorizontalcross-connect第十三頁(yè)，共一百五十一頁(yè)。Terminology(Cont.)Cross-Connect Afacilityenablingtheterminationofcableelements&theirinterconnection,and/orcross-connection,primarilybymeansofapatchcordorjumperEquipmentRoom Acentralizedspacefortelecomequiptthatservestheoccupantsofthebuilding(Bldg/CampusdistributorinISO11801)第十四頁(yè)，共一百五十一頁(yè)。Terminology(Cont.)TelecommunicationsCloset: Anenclosedspaceforhousingtelecomeqpt,cableterminations,andcross-connectcabling;thelocationforcross-connectionbetweenthebackboneandhorizontalfacilitiesWorkArea Abuildingspacewheretheoccupantsinteractwiththetelecomterminaleqpt第十五頁(yè)，共一百五十一頁(yè)。Terminology(Cont.)MainCross-Connect Across-connectbetween1stand2ndlevelbackbonecables,entrancecables,andequipmentcables(noISOname)IntermediateCross-Connect Across-connectbetween1stand2ndlevelbackbonecabling(noISOname)第十六頁(yè)，共一百五十一頁(yè)。Terminology(Cont.)HorizontalCross-Connect: Across-connectofhorizontalcablingtoothercabling,e.g.horizontal,backbone,orequipment(noISOname)TelecommunicationsOutlet Aconnectingdeviceintheworkareaonwhichhorizontalcableterminates第十七頁(yè)，共一百五十一頁(yè)。MediaRecommendedTelecomm.OutletHorizontalCross-connectMainCrossconnectIntermediateCross-connectTelecomm.OutletHorizontalCross-connectACBDD第十八頁(yè)，共一百五十一頁(yè)。CableDistancesUTP(VoiceTransmission)

MC-HC HC-IC MC-IC TO-HC

A B C D

800m 500m 300m 90mCat3or5UTP(up-to16or100MHz),andSTP(up-to300MHz)A B C D

90m 90m 90m 90m第十九頁(yè)，共一百五十一頁(yè)。CableDistances(Cont.)62.5micronsFiber MC-HC HC-IC MC-IC TO-HC A B C D

2000m 500m1500m 90mSingle-ModeFiber A B C D

3000m 500m2500m 90m第二十頁(yè)，共一百五十一頁(yè)。UnstructuredBackbone--MainframeTerminalsMainframe.........Clutteredandnoisycablerisers...第二十一頁(yè)，共一百五十一頁(yè)。UnstructuredBackbone--LAN

EachstationmustbephysicallyconnectedbyathickcoaxtappedtotheLANcoax,runningbyallstations.第二十二頁(yè)，共一百五十一頁(yè)。StructuredBackboneByusingaMUXorsimilardevice,abackbonecanbestructured.Asinglefiberpairreplacesmoundsofcoaxcable,andfloor-to-floortrafficissystematicallyorganized.WithStructurecomesenhancednetworkcontrolreliability,andefficiency.第二十三頁(yè)，共一百五十一頁(yè)。StructuredBackbone(Cont.)Structuredbackbone=structured,hierarchicalphysicalstarwiringscheme.MainframeMUXMUXMUX第二十四頁(yè)，共一百五十一頁(yè)。StructuredBackbone(Cont.)Thefirstinformationbackboneemergedinthemid1980’s.Anenterprisebackboneisanaggregatedatapath(acentralcommunicationhighway)forthetransportofallsignalsto/fromusersdistributedthroughouttheenterprise.Earlybackbonesweremainlymuxes.第二十五頁(yè)，共一百五十一頁(yè)。StructuredBackbone(Cont.)Theenterprisenetworkisusuallycomprisedofthreemainparts:Thehorizontalaccessportion:ConnectingindividualworkstationstowiringclosetsandmostoftenaccomplishedviaanintelligentcablingHub.TheBackboneportion:Facilitatingfloor-to-floororbuilding-to-buildingconnectivity.第二十六頁(yè)，共一百五十一頁(yè)。StructuredBackbone(Cont.)TheWideAreaNetworklinkHorizontalaccessBackboneWANInterface第二十七頁(yè)，共一百五十一頁(yè)。WhenareBackbonesneeded?CompaniesutilizingBackbonetechno-logyhavetypicallyoneormoreofthefollowingcommunicationneeds:Multipledataprotocolsandsignals.Heavynetworktraffictobesupportedsimultaneously.Multipleworkgroups,networks,andfacilitiesthatneedtobeinternetworked.Missioncriticalapplicationswherehighreliabilityandsecurityaremandatory.第二十八頁(yè)，共一百五十一頁(yè)。WhenareBackbonesneeded?(Cont.)Needtosupportvaryingmediaanddevicetypes.Ahighdegreeofupgradeability,sothatexistingequipmentcanbepreservedandhigherperformancehardwareandsoftwaresolutionscanbeimplementedseamlessly.Ahighdegreeofnetworkmoves,adds,andchanges,requiringthattheenterprisenetworkbehighlymanageable.第二十九頁(yè)，共一百五十一頁(yè)。Typesof(private)BackbonesThreebroadcategories: (1)Multiplexers-based. (2)LANBackbones.

FDDI,Ethernet,TokenRing,etc (3)CollapsedBackbones.

High-speedRouter,ATM.

第三十頁(yè)，共一百五十一頁(yè)。PublicBackbonesPublictelephone/datanetwork第三十一頁(yè)，共一百五十一頁(yè)。BackboneTopologiesStarCollapsedBackbonePBXsystemSwitch-basednetworks第三十二頁(yè)，共一百五十一頁(yè)。BackboneTopologies(Cont.)Ring.

Ex:FDDI.第三十三頁(yè)，共一百五十一頁(yè)。BackboneTopologies(Cont.)Hierarchical/InverseTree.Higherpowerathigherlevels.第三十四頁(yè)，共一百五十一頁(yè)。BackboneTopologies(Cont.)Mesh.Multipledatapathsbetweenpeerstations.TopologyreliesontheuseofRouters.第三十五頁(yè)，共一百五十一頁(yè)。BackboneBenefits+Makescomplexdistributedcomputingenvironmenteasiertomanage.+AllowsOrganizationstoeasilyupgradethesystem.+Createsanintegratedcommunicationpathcapableofaccommodatingtheenterprise’sdatatransferrequirementssafelyandcosteffectively.第三十六頁(yè)，共一百五十一頁(yè)。FiberOpticsManyoftheBackboneadvantagesareenabledbytheimplementationoffiber.Advantagesoffiber:+Abilitytocombinedata,voice&videosignalsoverasinglefiberpair.+Verylargebandwidth:(allowslargenumberofusers,iscosteffectiveandspace-conservative).+Increaseddatasecurity&reliability.第三十七頁(yè)，共一百五十一頁(yè)。Application/BandwidthHighcapacityBackboneisamusttosupportincreasingneedforbandwidth.

Application

Bandwidth

Digitalaudio 1.4Mbps

Compressedvideo(JPEG) 2-10MbpsDocumentReprographics 20-100MbpsCompressedbroadcast-qualityTV 20-100MbpsHigh-definitionfullmotionvideo 1-2GbpsChestX-Ray 4-40MbpsRemotequeryburst 1Mbps第三十八頁(yè)，共一百五十一頁(yè)。Multiplexer-BasedBackbonesThefirstBackboneswereMux-based.Designedforandcontinuedtobeusedpredominantlyinthemainframeenvironment.SuitableforsituationswhenamixtureofLANandhost-to-terminaltrafficneedstobesupportedviaacommonBackbone.AMuxisadevicethatsimultaneouslytransmitsseveralmessagesorsignalsacrossasinglechannelordatapath.第三十九頁(yè)，共一百五十一頁(yè)。Multiplexer-BasedBackbonesTwoprimarytypesofBackboneMuxesinusetoday:TimeDivisionMux(TDM).StatisticalorStatMux.第四十頁(yè)，共一百五十一頁(yè)。TimeDivisionMuxesATDMcombinessignalsontoahighspeedlink,andthensendsthosesignalssequentiallyatfixedtimeintervals.Eachuserinterfaceisallocatedatimeslotwithinwhichitsdataistransmitted.DataisusuallysentonecharatatimeCombinedsignalrates>100Mbps.第四十一頁(yè)，共一百五十一頁(yè)。TimeDivisionMuxesEthernetTokenRingMainframeEthernetTokenRingMainframeMTEMTEMTEMTE...AggregatepathwayMuxingDe-Muxing第四十二頁(yè)，共一百五十一頁(yè)。TDMStrengths+Dedicatedbandwidthpartitions

=>Guaranteedthroughput&noloss.+Versatile&scaleable.+LowcostcomparedtoStat.TDM.+ProvenReliabledatatransport.第四十三頁(yè)，共一百五十一頁(yè)。TDMWeaknesses--Bandwidthofidlesourcesislost.--Minimalinternetworkingcapability.第四十四頁(yè)，共一百五十一頁(yè)。StatisticalTDMBasedonthepremisethatstationsrarelyneedtotransmitdataconstantlyatfullavailablespeed.Attemptstomoveasmuchdataaspossibleacrossthecommonchannel.Combinedbandwidthofallsourcesexceedstheavailablebandwidth.Allocatestimeslotson-demand,constantlyevaluatingtrafficneedingtobesent(basedonpriority).第四十五頁(yè)，共一百五十一頁(yè)。Stat-Mux(Cont.)Incasedemandexceedscapacity,lower-prioritytrafficisoff-loadedintoabufferanddelayedforretransmissionduringanon-peakperiod=>Morecomplexfront-endmanagement. Greaterdegreeofintelligence. Greatercomputerpower.第四十六頁(yè)，共一百五十一頁(yè)。Stat-MuxStrengths+Supportsmoredatathanavailablebandwidth

=>betterbandwidthutilization.+Criticaldatacanbegivenhigherpriority.第四十七頁(yè)，共一百五十一頁(yè)。Stat-MuxWeaknesses--Requiresmoremanagementandmoreexpensivetooperate.--Lowprioritydatacansufferexcessivedelays.--Datamaygetlost. (Noguaranteedbandwidth)第四十八頁(yè)，共一百五十一頁(yè)。EmergingBackboneTechnologiesThreeofthemostpromisingBackbonetechnologiesare:AsynchronousTransferMode(ATM).SynchronousOpticalNetwork(SONET).FibreChannel.第四十九頁(yè)，共一百五十一頁(yè)。ATMToday’scollapsedBackbonesarebasedonRoutertechnology.Tomorrow’scollapsedBackboneswillbebasedonswitchingtechnology.ATMispredictedtobeatthecoreoftheswitchingtechnology.ATMishailedasthefirstsolutionthatwillerasethebarriersbetweenLANsandWANs.第五十頁(yè)，共一百五十一頁(yè)。ATM(Cont.)ATMATMServerWANInterfaceRouterBackbone第五十一頁(yè)，共一百五十一頁(yè)。ATMBenefits+CombinesbestfeaturesofMuxesandLANBackbones.+ATMridesontopofahighlyscaleablephysicallayerprotocolsuchasFiberchannelandSONET.+Short&fixed-lengthcells=>Relativelylowcosthardwareimplementation.+Canaccommodatebothreal-timeandnon-real-timedata.第五十二頁(yè)，共一百五十一頁(yè)。ATMBenefits(Cont.)+Provideshighthroughput.+ATMisnotprotocol-dependent.AnypacketformatcanbemappedintoATMcellsandtransported.

=>Itisanidealdatatransfersystemfor changingLANenvironments.第五十三頁(yè)，共一百五十一頁(yè)。HowATMWorks?DataUnits:Fixed-lengthcellsofsize53byteseach(5Header+48payload).OperatesattheequivalentofMACsublayer.OperatesabovephysicallayerwhichcouldbeSONET,Fibrechannel,...Connection-oriented.UniversaltransfermodeforallB-ISDNservices.Layeredarchitecture.第五十四頁(yè)，共一百五十一頁(yè)。ATMLayeredArchitectureHigherLayersUserServices&applicationsATMAdaptationLayerATMLayerPhysicalMediumDependentLayerFragmentationandde-fragmentationofframesCellheaderinsertion/removalCellrelaying&multiplexingConnectionestablishmentTransmission&receiptofbitsSynchronization第五十五頁(yè)，共一百五十一頁(yè)。HowATMWorks?DatapacketAALATMPhysicalLayer第五十六頁(yè)，共一百五十一頁(yè)。HowATMWorks(Cont.)?PhysicalLayerATMEntireprocessisreversedOverheadEnvelopeCell第五十七頁(yè)，共一百五十一頁(yè)。ExamplesofATMSwitchesFORESystemsASX-200BX(2.5Gbpsbackplane)ASX-1000(10Gbpsbackplane)CISCOSystemsNWAYS8260(5Gbpsbackplane)BayNetworksCentillian-100:campusATMswitch(3.2Gbpsbackplane)第五十八頁(yè)，共一百五十一頁(yè)。ExamplesofATMSwitches(Cont.)IBMNWAYS8260(5Gbpsbackplane)MADGENetworksCollage740:CampusATMswitch(5Gbpsbackplane)ALCATEL1100LSSSeries550A第五十九頁(yè)，共一百五十一頁(yè)。SynchronousOpticalNetworkSONETisANSI&ITUStandard.Firststandardopticalinterface.UsedinthepublicnetworkandisbeingadoptedasaprivateBackbonesolution.AmericanSONETStandard:RatesstartatOC-1 : 51.84MbpsScalinguptoOC-48 : 2.48Gbps第六十頁(yè)，共一百五十一頁(yè)。SONET(Cont.)EuropeanSDH:InitialRate:SDH-1=OC-3:155.52MbpsSONETprovidesatransportpayloadenvelopeandframingformat.Anytypeofdataistransparentlytransmittedwithlowdelays.SONETiscurrentlydefinedforusewithsinglemodefiber.第六十一頁(yè)，共一百五十一頁(yè)。FibreChannelANSIX3T9.3Standard.Developedashighspeedinterfaceforlinkingmainframesandtheirperipherals.BettersuitedasaprivateBackbonebecauselessoverheadlowestimplementationmulti-modefiber第六十二頁(yè)，共一百五十一頁(yè)。FibreChannel(Cont.)IsalsohighlyexpandableInitialRate :100MbpsScalesupto :1.6GbpsHasatransportpayloadenvelope第六十三頁(yè)，共一百五十一頁(yè)。LANBackbonesUnlikeMuxeswhicharecapableoftransmittinganarrayofdata,host-to-host,voiceandvideosignals,LANBackbonesarededicatedexclusivelyforLANcommunication.Actually,anylegacyLANsuchasEthernetorTokenRingcanbecalledabackboneLANsconstitutetheprimarydatapaths.第六十四頁(yè)，共一百五十一頁(yè)。LANBackbones(Cont.)InthebroadercontextofBackbones,thekeyLANstandardthathasfar-reachingBackbone-basedapplicationsistheFiberDistributedDataInterface(FDDI).FDDIis(still?)thedominantLANBackboneinuse.Itprovidesstandards-basedconnectivityforlegacyLANs(Ethernet&TokenRing).第六十五頁(yè)，共一百五十一頁(yè)。LANBackbones(Cont.)TokenRingEthernetTokenRingEthernetEthernetTokenRingAlloftheprotocolsareconvertedtotheFDDItransportprotocolDataisBridged/Routedfromthehigh-speedBackbonetodestinationLAN第六十六頁(yè)，共一百五十一頁(yè)。LANBackbones(Cont.)FDDIcomplementsexistingLANsbyprovidingahigh-speedpathuponwhichallLANprotocolscanbetransported.TypicalFDDIapplications:BackboneconnectivitybetweenLANsinabuildingorcampus.LANforhigh-endgraphics&CAD/CAMworkstationsConnectiondeviceforhost-to-hostorBackbone-to-Backboneapplications.第六十七頁(yè)，共一百五十一頁(yè)。FDDIStrengths+FDDIistailor-madeandveryeffectiveasahigh-speedLANforworkstationtrafficandasaBackboneforLANs.+Providesaframeworkforinter-networkingbetweenvariousLANprotocols.第六十八頁(yè)，共一百五十一頁(yè)。FDDIStrengths(Cont.)+ComparedtolegacyLANs,FDDIprovidesgreaterdatacapacityandperformance,transmittingat100Mbps.+Canaccommodatelargenetworksofupto500Backbonenodes.第六十九頁(yè)，共一百五十一頁(yè)。FDDIStrengths(Cont.)+Becauseofitsdual-ringarchitecture,FDDIoffersahighdegreeofnetworkavailability/reliability.+UsingTokenpassing,trafficisdealtwithonadeterministicbasis.+Provideslongdistancecommunication (Ringperimetercanbe100Kmwithadistanceofupto2KmbetweenStations)第七十頁(yè)，共一百五十一頁(yè)。FDDIWeaknesses--CanaccommodateLANtrafficonly.Notcapablefortransportingreal-timesignals(voice,host-to-terminal,etc.)--Nonscaleable(fixedat100Mbps).--Highimplementationcost(Processorintensive).第七十一頁(yè)，共一百五十一頁(yè)。HowFDDIWorks?Itisatokenpassingfiberringwithadatarateof100Mbps.Ringcanbeaslargeas100Kmwithadistanceof2Kmbetweenstations.Mostprevalentstandardismulti-modefiber.However,somemanufacturersareproducingmulti-modetosingle-modeFDDIadapter.第七十二頁(yè)，共一百五十一頁(yè)。HowFDDIWorks?(Cont.)OthersproposedamendmentstothestandardtosupportFDDIontwistedpair(CDDI).RoutersareusedtoconvertcompetingLANprotocolstoFDDIandback.第七十三頁(yè)，共一百五十一頁(yè)。HowFDDIWorks?(Cont.)Dual-counterrotatingrings:Primarylinkforcarryingdata.Secondarylinkforfailurerecovery.Intheeventofanodeorcablefailure,thedataontheprimarylinkwrapsontothesecondarylink,makingaU-turn,thusmaintainingringintegrity.第七十四頁(yè)，共一百五十一頁(yè)。HowFDDIWorks?(Cont.)FDDIFDDIFDDIXX第七十五頁(yè)，共一百五十一頁(yè)。FDDISpecificationANSIStandard.Ringaslargeas100Kmwithadistanceof2Kmbetweenstations.62.5mcore/125mcladding.1300nano-meterLEDtransmitterTwotypesofFDDInetworkingdevices:ClassAdeviceshavedualattachment.ClassBaretypicallyworkstations.第七十六頁(yè)，共一百五十一頁(yè)。FDDISpecificationClassADevicesToexploitcounter-rotatingrings.ThefailurewrappingfeatureisimplementedthroughClassAdevices.Canbeanynetworkingdevice,butareusuallyBridges,Routers,Concentrators,Servers,orotherdevicescomprisingthenetworkBackbone.第七十七頁(yè)，共一百五十一頁(yè)。ClassADevices(Cont.)Eachdual-attachedstationconstantlyreceivesHandshakinginformationfromitsneighborsviathesecondarylink.IfstationstopsreceivingHandshakinginformation,itwrapsdatafromtheprimarytothesecondaryringsothatthedisablednodeisavoidedandringintegrityismaintained.第七十八頁(yè)，共一百五十一頁(yè)。FDDISpecification(Cont.)ClassBDevicesTheyaresingle-attachedstations.Theyaretypicallyworkstations,printers,andothernodesthatareattachedonlyindirectlytotheprimarylink.Theyaccesstheringbypluggingintoaconcentratorthatisdual-attachedtothering.AnFDDInetworkcanoperatewithupto500dual-attachedstations.第七十九頁(yè)，共一百五十一頁(yè)。FDDISpecification(Cont.)AABBBBBBBBBBBClassA第八十頁(yè)，共一百五十一頁(yè)。FDDIFramePreamble(Beginning)StartofFrameFrameControlDestination@Source@DataCRCEndofFrameFrameStatus(End)第八十一頁(yè)，共一百五十一頁(yè)。CollapsedBackboneBasedontoday’shigh-speedRouters.SometimescalledBackboneRouters.Thisschemecollapsesvastamountsofenterprisedataontothebackplaneofahigh-throughputRouter.LANconnectionsarestarredbacktothecentralcollapsedbackboneforhigh-speedinternetworking.第八十二頁(yè)，共一百五十一頁(yè)。CollapsedBackbone(Cont.)ThecollapsedBackboneservesastheGate-Keeperfortheentireenterprisenetworkandprovidessophisticatedprotocolconversionandroutingalonganultrahigh-speedGigabitbackplane.Multi-LANHubsareusedtoconnectusersonindividualfloors.第八十三頁(yè)，共一百五十一頁(yè)。CollapsedBackbone(Cont.)Multi-LANHubMulti-LANHubMulti-LANHubMulti-LANHubCollapsedBackboneWANInterface第八十四頁(yè)，共一百五十一頁(yè)。CollapsedBackboneStrengths+IncreasedlevelofLANManagement,downtothesegmentlevel,sinceallLANsaredirectedbacktothecentralBackboneforrouting.+SupportsinternetworkingbetweenenterpriseLANs.+HasGigabitthroughput,supportingdozensofLANsstarredbacktoahighlymanagedlocation(nodatabottlenecks).第八十五頁(yè)，共一百五十一頁(yè)。CollapsedBackbonesStrengths(Cont.)+Centrallylocatedtoreducecosts,increasemanageability,andminimizereliabilityproblems.+Don’ttranslateLANsignalsintoanintermediatesignal(asinFDDI).+Keepsallnetworkprotocolsinacentraldatabase,ensuringproperroutingofalldatapackets+Natural/smoothtransitiontoright-sizing.第八十六頁(yè)，共一百五十一頁(yè)。CollapsedBackbonesWeaknesses--OftenrequireHubsorphysicalBackbonestoprovideend-userconnectivity.--Areprocessorandsoftwareintensive,thusrequiringmoremaintenancethanatypicalHub(MTBF-Router=20,000hrs,

MTBF-Intelligent-Hub>100,000hrs.)--Don’tsupportHost-to-Terminaltraffic.第八十七頁(yè)，共一百五十一頁(yè)。RoutersTechnologyRoutersprovideagreaterdegreeofintelligencethanBridges.RoutersoperateontheNetworkLayertojoindifferentnetworkssuchasX.25-to-FDDI,X.25-to-Ethernet,etc.第八十八頁(yè)，共一百五十一頁(yè)。Routersvs.BridgesAddressing>Routersareexplicitlyaddressed.>Bridgesarenotaddressed.Thestationsareunawareoftheirexistence.Data>Routersaccessandusemultiplesourcesofdatatomakeappropriateroutingdecision.>Bridgesuseonlysourceanddestinationaddresses.第八十九頁(yè)，共一百五十一頁(yè)。Routersvs.Bridges(Cont.)Message>Routerscanopenmessages&manipulate/fragmentamessagecontents.TheycanprovideconnectionservicesbetweenLANsthatusedifferentmessagelengths.>Bridgeshavenoaccesstomessagecontts.Feedback>Routersprovidefeedbackonnetworkconditionstoend-users.>Bridgescannot.第九十頁(yè)，共一百五十一頁(yè)。Routersvs.Bridges(Cont.)Forwarding>Routersforwardamessagetospecificdestinationusingthebestroute(intermediatenetsarecountedashops)>Bridgesforwardamessagetoanoutgoingnetwork.Priority>Routerssupportdifferentclassesofservice>Bridgestreatallpacketsidentically.第九十一頁(yè)，共一百五十一頁(yè)。Routersvs.Bridges(Cont.)SecurityBothBridgesandRoutersprovidetheabilitytoput“securitywalls”aroundspecificstations.>RoutersgenerallyprovidegreatersecuritythanBridgesbecause:

+

theyareaddresseddirectly +theyaccessmoredata.第九十二頁(yè)，共一百五十一頁(yè)。Routersvs.Bridges(Cont.)Overall,RoutersprovideEnhancednetworksegmentationandsecurity.Improvedreliabilitysincealternativepathscanbeused.Improvedbandwidthutilization.Abilitytolinkmanynetworks-goingwellbeyondtheseven-hop-limitofBridges(notconfrontedwithtimedelayconstraintsasBridge-basedsystems).第九十三頁(yè)，共一百五十一頁(yè)。BackboneExamplesAllBackbonesolutionsarebasedontheuseoffiberbecausefiber:FormsthebasesforallfutureBackbonemigrations.Enablesnetworkmanagerstoextendthelifeoftheircablingplants.Enablesthenetworktoeasilymigratetobettertechnology(networkapplicationsoftwareornetworkhardware).第九十四頁(yè)，共一百五十一頁(yè)。Mux-BasedBackboneNetworkEnvironmentcharacteristics:Largemainframeusewithanexistingmainframe-basednetworkmanagementsystem(suchasSNA/Netview).Several/multi-storybuildings.MultiplesignaltypesDuctspaceisatapremium.ClustersofworkgroupLANsspreadthroughouttheorganization第九十五頁(yè)，共一百五十一頁(yè)。Mux-basedBackbone(Cont.)Multi-protocolMultiplexerTokenRingEthernetTerminalsFiberBackboneFiberTwistedPair第九十六頁(yè)，共一百五十一頁(yè)。Client-ServerBackboneEnvironmentcharacteristics:Severalhigh-poweredcentralserversforsharedcorporateresources/applications.AcurrentHub-basedsolution.NeedtosupportmultipleLANs(Ethernet,TokenRing,FDDI).Ahighdegreeoflocaltrafficandthereforetheneedtocreatesubnetworksandseparateworkgroups.第九十七頁(yè)，共一百五十一頁(yè)。Client-ServerBackbone(Cont.)Multi-LANHubTokenRingEthernetFDDIBackboneNetworkManagement(SNMP)Servers...第九十八頁(yè)，共一百五十一頁(yè)。CollapsedBackboneNetworkEnvironmentcharacteristics:SeverallegacyLANsandahighdegreeoftraffic.Varyingnetworkresourcestobeshared.Needforcentralizedmanagement.第九十九頁(yè)，共一百五十一頁(yè)。CollapsedBackbone(Cont.)Multi-LANHubRouterPublicWANMulti-LANHubNetworkManagement(SNMP)TokenRingEthernetFiberFileServerCollapsedBackbone第一百頁(yè)，共一百五十一頁(yè)。HybridBackboneNetworkEnvironmentcharacteristics:NeedtosupportMainframe(host-to-terminal)users,LANtraffic,andWANaccess.Alargenumberofusers,multiplelocations,andvariousremotesites.GrowingLANsandincreasingtraffic.第一百零一頁(yè)，共一百五十一頁(yè)。HybridBackbone(Cont.)Multi-LANHubMulti-LANHubTokenRingEthernetTerminals...Terminals...RouterWANFileServerFiberMainframeCollapsedBackbone第一百零二頁(yè)，共一百五十一頁(yè)。NetworkDevelopmentLifeCycleEffectiveNetworking&itsImportance.NDLCDefinition.NDLCPhases:Analysis.Design.SimulationandPrototyping.Implementation.MonitoringandManagement.第一百零三頁(yè)，共一百五十一頁(yè)。Why?!!Mostnetworkingsystemsdonotfollowsoundengineeringtechniquesinarchitectingthenetwork.Networksbuiltinanad-hocfashionarenotwellstructured.Manyperformancebottlenecks.Noorlittlefutureexpandability.第一百零四頁(yè)，共一百五十一頁(yè)。NDLCDefined Adesignmethodologytocreateandmaintainanefficiententerprisenetworkedsystemthatmeetsdesiredobjectives.第一百零五頁(yè)，共一百五十一頁(yè)。NDLCPhasesAnalysis.Design.Prototypingandsimulation.Implementation.Monitoringandmanagement.第一百零六頁(yè)，共一百五十一頁(yè)。NDLCAnalysisDesignSimulation&PrototypingImplementationMonitoring&Management第一百零七頁(yè)，共一百五十一頁(yè)。AnalysisBeforemakinganydecisionsonnetworkarchitecture,topology,speed,orcost,anappropriateinvestigationmustbeperformedbyresponsibleanalyst(s)togetherwith:Users.Applicationproviders.Networkingdevicessuppliers.Financingentity(Decisionmakers)!第一百零八頁(yè)，共一百五十一頁(yè)。PreparingaSiteSurveyAsitesurveymustbedonebeforeproposing&committingtonewdesign.Asitesurveyshouldincludeallexistinginterconnectionsaswellasphysicalandlogicalnetworklayout.第一百零九頁(yè)，共一百五十一頁(yè)。SiteSurvey(Cont.)Toprepareasitesurvey,documentallaspectsoftheinstallation:ExisttinggroundingUnderlyingcablestructure,distancesfromclosets,andqualityDatalinktopologiesinuse(Ethernet,etc.)Networkhardware(Hubs,servers,routers,bridges,switches,NICs,etc.)第一百一十頁(yè)，共一百五十一頁(yè)。SiteSurvey(Cont.)Interconnections(Cross-connectfields,pushdownblocks,terminat