switch

Definition

Exchangeisatechnologythatsendstheinformationtobetransmittedtothecorrespondingroutethatmeetstherequirementsbymanuallyorautomaticallycompletingthemethodaccordingtotheneedsofthetwoendsofthecommunicationtotransmitinformation.Collectively.SwitchescanbedividedintoWANswitchesandLANswitchesaccordingtodifferentworkingpositions.Thewide-areaswitchisadevicethatcompletestheinformationexchangefunctioninthecommunicationsystem,anditisappliedatthedatalinklayer.Theswitchhasmultipleports,eachporthasabridgingfunction,andcanbeconnectedtoalocalareanetworkorahigh-performanceserverorworkstation.Infact,switchesaresometimescalledmulti-portbridges.

Thenetworkswitchisadevicetoexpandthenetwork,whichcanprovidemoreconnectionportsinthesub-networktoconnectmorecomputers.Withthedevelopmentofthecommunicationsindustryandtheadvancementoftheinformatizationofthenationaleconomy,thenetworkswitchmarkethasshownasteadyupwardtrend.Itiscost-effective,highlyflexible,relativelysimpleandeasytoimplement.EthernettechnologyhasbecomethemostimportantLANnetworkingtechnologytoday,andnetworkswitcheshavealsobecomethemostpopularswitches.

SwitchistheEnglishnameoftheswitch.Thisproductisanupgradeoftheoriginalhub,anditisnotverydifferentfromthehubinappearance.Becausethetwoendsofthecommunicationneedtotransmitinformation,andtheinformationtobetransmittedissenttothecorrespondingrouterthatmeetstherequiredstandardsthroughequipmentormanually,thistechnologyisswitchtechnology.Analyzedinabroadsense,theequipmentthatrealizestheinformationexchangefunctioninthecommunicationsystemistheswitch.

Developmenthistory

"Switch"isanimportedword,derivedfromtheEnglish"Switch",theoriginalmeaningis"switch",whentheChinesetechnologycommunityintroducedthisterm,itwastranslatedas"Exchange"".InEnglish,theverb"exchange"andthenoun"switch"arethesameword(notethat"exchange"hererefersspecificallytotheexchangeofsignalsintelecommunicationstechnology,andisnotthesameconceptastheexchangeofgoods).

In1993,LANswitchingequipmentappeared,andin1994,adomesticupsurgeofswitchingnetworktechnologystarted.Infact,theswitchingtechnologyisaswitchingproductwithsimplification,lowprice,highperformanceandhighportdensity.ItembodiesthecomplexswitchingtechnologyofbridgingtechnologyinthesecondlayeroftheOSIreferencemodel.Likethebridge,theswitchforwardsthedecisioninformationrelativelysimplyaccordingtotheMACaddressineachpacket.Andthisforwardingdecisiongenerallydoesnotconsiderotherdeeperinformationhiddeninthepacket.Thedifferencewithbridgesisthattheswitchforwardingdelayisverysmall,andtheoperationisclosetotheperformanceofasingleLAN,whichfarexceedstheforwardingperformancebetweenordinarybridgedInternetnetworks.

SwitchingtechnologyallowsbandwidthadjustmentsforsharedanddedicatedLANsegmentstoalleviatebottlenecksintheflowofinformationbetweenLANs.ExistingEthernet,FastEthernet,FDDIandATMtechnologyswitchingproducts.

Similartotraditionalbridges,switchesprovidemanynetworkinterconnectionfunctions.Theswitchcaneconomicallydividethenetworkintosmallconflictingdomainsandprovidehigherbandwidthforeachworkstation.Thetransparencyoftheprotocolallowstheswitchtobedirectlyinstalledinamulti-protocolnetworkwithsimplesoftwareconfiguration;theswitchusesexistingcables,repeaters,hubs,andworkstationnetworkcards,withouttheneedforhigh-levelhardwareupgrades;theswitchistransparenttoworkstationsYes,suchmanagementoverheadislow,whichsimplifiestheoperationsofadding,moving,andchangingnetworknodes.

Usingaspeciallydesignedintegratedcircuit,theswitchcanforwardinformationinparallelonallportsatalinerate,providingmuchhigheroperatingperformancethantraditionalbridges.Application-specificintegratedcircuittechnologyenablestheswitchtoachievetheaboveperformancewithmoreports,anditsportcostislowerthanthatoftraditionalbridges.

Classification

Fromabroadperspective,networkswitchesaredividedintotwotypes:WANswitchesandLANswitches.WANswitchesaremainlyusedinthetelecommunicationsfieldtoprovideabasicplatformforcommunications.TheLANswitchisusedinthelocalareanetworktoconnecttoterminalequipment,suchasPCsandnetworkprinters.Fromthetransmissionmediumandtransmissionspeed,itcanbedividedintoEthernetswitches,fastEthernetswitches,GigabitEthernetswitches,FDDIswitches,ATMswitches,andtokenringswitches.Fromthescaleofapplication,itcanbedividedintoenterprise-levelswitches,department-levelswitches,andworkgroupswitches.Thescalesofdifferentmanufacturersarenotcompletelythesame.Generallyspeaking,enterprise-levelswitchesarerack-mounted,anddepartment-levelswitchescanberack-mounted(withasmallnumberofslots)orfixed-configurationtype.Thelevelswitchisafixedconfigurationtype(thefunctionisrelativelysimple).Ontheotherhand,fromtheperspectiveofapplicationscale,whenusedasabackboneswitch,aswitchthatsupportslarge-scaleenterpriseapplicationswithmorethan500informationpointsisanenterprise-levelswitch,andaswitchthatsupportsmedium-sizedenterpriseswithlessthan300informationpointsisadepartment-levelswitch,and100Switcheswithinthisinformationpointareworkgroup-levelswitches.

Ethernetswitches

Withtherapiddevelopmentofcomputersandtheirinterconnectiontechnology(alsoknownas"networktechnology"),Ethernethasbecomethemostpopularshort-circuitsofar.Distancetothesecond-tiercomputernetwork.ThecorecomponentofEthernetistheEthernetswitch.

Whetheritismanualswitchingorprogram-controlledswitching,itisforthetransmissionofvoicesignals,anditisa"circuitswitching"thatrequiresanexclusiveline.TheEthernetisacomputernetworkthatneedstotransmitdata,soituses"packetswitching."Butnomatterwhichswitchingmethodisadopted,theswitch'sfeatureofproviding"exclusiveaccess"betweentwopointswillnotchange.AsfarasEthernetequipmentisconcerned,theessentialdifferencebetweenaswitchandahubisthatwhenAsendsamessagetoB,ifitpassesthroughthehub,allnetworknodesconnectedtothehubwillreceivethisinformation(thatis,itwillbesentintheformofbroadcast),Butthenetworkcardatthehardwarelevelwillfilterouttheinformationthatisnotsenttothemachine;andifitpassesthroughtheswitch,unlessAinformstheswitchtobroadcast,otherwisetheinformationsenttoBwillneverbereceived(obtainingthecontrolauthorityoftheswitchtomonitorthesituationexcept).

Accordingtomarketdemand,EthernetswitchmanufacturershaveintroducedLayer3orevenLayer4switches.Butinanycase,itscorefunctionisstillLayer2Ethernetdatapacketswitching,butwithacertainabilitytoprocessdatapacketsattheIPlayerorevenhigherlayers.Thenetworkswitchisadevicethatexpandsthenetworkandcanprovidemoreconnectionportsinthesub-networktoconnectmorecomputers.Withthedevelopmentofthecommunicationsindustryandtheadvancementoftheinformatizationofthenationaleconomy,thenetworkswitchmarkethasshownasteadyupwardtrend.Ithasthecharacteristicsofhighperformance-priceratio,highflexibility,relativelysimple,andeasytoimplement.

OpticalSwitch

Opticalswitchingisthenextgenerationswitchingtechnologybeingdeveloped.Allswitchingtechnologiesarebasedonelectricalsignals.Evenfiberopticswitchesconvertopticalsignalstoelectricalsignals,andafterswitchingprocessing,theopticalsignalsarethenconvertedbacktoanotheropticalfiber.Duetothelowphotoelectricconversionrateandthephysicalbottleneckofthecircuitprocessingspeed,peoplehopetodesignan"opticalswitch"thatdoesnotrequirephotoelectricconversion.Theinternalpartisnotacircuitbutanopticalcircuit,andthelogicelementisnotaswitchingcircuit.Itistheswitchopticalpath.Thiswillgreatlyincreasetheprocessingspeedoftheswitch.

Remoteconfiguration

Inadditiontothedirectconnectiontothecomputerthroughthe"Console"port,theswitchcanalsobeconnectedthroughanormalport.Atthistime,youcannotuselocalconfigurationtoconfiguretheswitch.Instead,youneedtoimplementtheswitchconfigurationthroughTelnetoraWebbrowser.Thespecificconfigurationmethodisasfollows:

1,Telnet

Telnetprotocolisaremoteaccessprotocol,whichcanbeusedtologintotheswitchforconfiguration.

AssumingtheswitchIPis:192.168.0.1,itonlytakestwostepstoconfiguretheswitchthroughTelnet:

Step1,clickstart,run,andenter"Telnet192.168.0.1"

Step2,afterinputting,clickthe"OK"button,orclicktheEnterkeytoestablishaconnectionwiththeremoteswitch.Then,theswitchcanbeconfiguredandmanagedaccordingtoactualneeds.

2,Web

Throughthewebinterface,youcansettheswitch,themethodisasfollows:

Step1,runthewebbrowser,enterintheaddressbarSwitchIP,pressEnter,andthefollowingdialogboxwillpopup.

Step2,enterthecorrectusernameandpassword.

Step3,theconnectionisestablished,youcanentertheswitchconfigurationsystem.

Step4,followthepromptstosettheswitchandmodifytheparameters.

Features

Becausetheswitchhasahigh-bandwidthinternalswitchingmatrixandabackbus,andallportsareconnectedtothebackbus,thedatacanbetransferredthroughtheinternalswitchingmatrix.Thepacketisdirectlyandquicklytransmittedtothedestinationnodeinsteadofallnodes,sothatnetworkresourcesarenotwasted,resultinginveryhighefficiency.Atthesametime,thesecurityofdatatransmissionisveryhighduringthisprocess,anditiswelcomedandgenerallypraisedbyusers.

Thedifferencethateachportofahubsharesthesamebandwidthisthatthedatabandwidthoftheswitchisexclusive.Underthispremise,inthesametimeperiod,theswitchcantransmitdatabetweenmultiplenodes,andeachnodecanbetreatedasanindependentnetworksegmentandenjoyafixedpartofthebandwidthindependently,sothatthereisnocommunicationwithotherdevices.Necessaryforcompetitionandpracticality.

Workingprinciple

TheswitchworksonthesecondlayeroftheOSIreferencemodel,thedatalinklayer.TheCPUinsidetheswitchwillformaMACtablebymatchingtheMACaddressandtheportwheneachportissuccessfullyconnected.Infuturecommunications,datapacketssenttothisMACaddresswillonlybesenttoitscorrespondingport,notallports.Therefore,theswitchcanbeusedtodividethedatalinklayerbroadcast,thatis,thecollisiondomain;butitcannotdividethenetworklayerbroadcast,thatis,thebroadcastdomain.

Theswitchhasahigh-bandwidthbackbusandinternalswitchingmatrix.Allportsoftheswitchareconnectedtothisbackbus.Afterthecontrolcircuitreceivesthedatapacket,theprocessingportwilllookuptheaddresscomparisontableinthememorytodeterminethedestinationMAC(thehardwareaddressofthenetworkcard)andtheNIC(networkcard)connectionOnwhichport,thedatapacketisquicklytransmittedtothedestinationportthroughtheinternalswitchingmatrix.IfthedestinationMACdoesnotexist,itwillbebroadcasttoallports.Afterreceivingtheportresponse,theswitchwill"learn"thenewMACaddressandaddittotheinternalMACaddresstable.Theswitchcanalsobeusedto"segment"thenetwork.BycomparingtheIPaddresstable,theswitchallowsonlynecessarynetworktraffictopassthroughtheswitch.Throughthefilteringandforwardingoftheswitch,thecollisiondomaincanbeeffectivelyreduced.

Port

Theswitchcantransmitdatabetweenmultipleportpairsatthesametime.Eachportcanberegardedasanindependentphysicalnetworksegment(note:non-IPnetworksegment),andthenetworkequipmentconnectedtoitenjoysthefullbandwidthindependently,withoutcompetingwithotherequipmentforuse.WhennodeAsendsdatatonodeD,nodeBcansenddatatonodeCatthesametime,andbothtransmissionsenjoythefullbandwidthofthenetworkandbothhavetheirownvirtualconnections.Ifa10MbpsEthernetswitchisusedhere,thenthetotalcirculationoftheswitchatthistimeisequalto2×10Mbps=20Mbps,andwhena10MbpssharedHUBisused,thetotalcirculationofaHUBwillnotexceed10Mbps.Inshort,aswitchisanetworkdevicebasedonMACaddressrecognitionandcapableofencapsulatingandforwardingdataframes.Theswitchcan"learn"theMACaddressandstoreitintheinternaladdresstable.Byestablishingatemporaryswitchingpathbetweentheoriginatorandthetargetreceiverofthedataframe,thedataframecandirectlyreachthedestinationaddressfromthesourceaddress.

Theworkingprincipleofdatatransmission

Afteranynodeoftheswitchreceivesthedatatransmissioninstruction,itquicklysearchestheaddresstablestoredinthememory,soastoconnecttotheMACaddressofthenetworkcardThelocationisconfirmed,andthenthedataistransmittedtothenode.Ifthecorrespondingpositionisfoundintheaddresstable,itwillbetransmitted;ifnot,theswitchwillrecordtheaddresstofacilitatethenextsearchanduse.Generally,theswitchonlyneedstosendtheframetothecorrespondingpoint,anddoesnotneedtosendittoallnodeslikeahub,thussavingresourcesandtime,andimprovingthedatatransmissionrate.

Datatransmissionmethod

Datatransmissionthroughexchangeisactuallythedatatransmissionmethodoftheswitch.Theprevioushubsusedmoresharingmethodstotransmitdata,andtherewasnowaytorequestthespeedofcommunication.Thehubsharingmethod,alsoknownasthesharednetwork,usesthehubastheconnectiondeviceandonlyhasonedirectionofdataflow,sotheefficiencyofnetworksharingisverylow.Relativelyspeaking,theswitchcanidentifythecomputersconnectedtoitself,andusethephysicaladdressofeachcomputer'snetworkcard,whichiscommonlyreferredtoastheMACaddress,formemoryandidentification.Undersuchapremise,thereisnoneedtoperformbroadcastsearch,butcandirectlyfindthecorrespondinglocationofthememorizedMACaddressanduseatemporarydedicateddatatransmissionchanneltocompletethedatabetweenthetwonodeswithoutexternalinterference.Transmissionofcommunications.Sincetheswitchalsohasafull-duplextransmissionmethod,itisalsopossibletoformathree-dimensionalandcrossdatatransmissionchannelstructurebysimultaneouslyestablishingtemporarydedicatedchannelsbetweenmultiplepairsofnodes.

Purpose

Themainfunctionsoftheswitchincludephysicaladdressing,networktopology,errorchecking,framesequenceandflowcontrol.Theswitchalsohassomenewfunctions,suchassupportforVLAN(virtuallocalareanetwork),supportforlinkaggregation,andsomeevenhavethefunctionofafirewall.

Learning:

TheEthernetswitchunderstandstheMACaddressofthedeviceconnectedtoeachport,andmapstheaddresstothecorrespondingportandstoresitintheswitchcacheIntheMACaddresstable.

Forwarding/Filtering:

WhenthedestinationaddressofadataframeismappedintheMACaddresstable,itisforwardedtotheportconnectedtothedestinationnodeInsteadofallports(ifthedataframeisabroadcast/multicastframe,itwillbeforwardedtoallports)

eliminateloops:

WhentheswitchincludesaredundantWhenthereisaremainingloop,theEthernetswitchavoidsthegenerationofloopsthroughthespanningtreeprotocol,andatthesametimeallowstheexistenceofbackuppaths.

Inadditiontobeingabletoconnecttothesametypeofnetwork,theswitchcanalsointerconnectdifferenttypesofnetworks(suchasEthernetandFastEthernet).Nowadays,manyswitchescanprovidehigh-speedconnectionportsthatsupportFastEthernetorFDDI,etc.,whichareusedtoconnecttootherswitchesinthenetworkorprovideadditionalbandwidthforkeyserversthattakeupalotofbandwidth.

Generallyspeaking,eachportoftheswitchisusedtoconnecttoanindependentnetworksegment,butsometimesinordertoprovidefasteraccessspeed,wecanconnectsomeimportantnetworkcomputersdirectlytotheswitchOntheport.Inthisway,keyserversandimportantusersofthenetworkhavefasteraccessspeedsandsupportgreaterinformationflow.

Finally,brieflysummarizethebasicfunctionsoftheswitch:

1.Likeahub,theswitchprovidesalargenumberofportsforcableconnection,sothatthestartopologycanbeusedforwiring.

2.Likerepeaters,hubs,andbridges,whenitforwardsframes,theswitchregeneratesanundistortedsquareelectricalsignal.

3.Likeabridge,theswitchusesthesameforwardingorfilteringlogiconeachport.

4.Likeabridge,theswitchdividestheLANintomultiplecollisiondomains,andeachcollisiondomainhasanindependentbroadband,thusgreatlyimprovingthebandwidthoftheLAN.

5.Inadditiontothefunctionsofabridge,hub,andrepeater,theswitchalsoprovidesmoreadvancedfeaturessuchasvirtuallocalareanetwork(VLAN)andhigherperformance.

TraditionalswitchesevolvedfrombridgesandbelongtothesecondlayerofOSI,thedatalinklayerequipment.ItaddressesaccordingtotheMACaddress,selectstheroutethroughthestationtable,andtheestablishmentandmaintenanceofthestationtableareautomaticallycarriedoutbytheswitch.TherouterbelongstothethirdlayerofOSI,thatis,thenetworklayerdevice.ItaddressesaccordingtotheIPaddressandisgeneratedthroughtheroutingtableroutingprotocol.Thebiggestadvantageoftheswitchisthatitisfast.BecausetheswitchonlyneedstoidentifytheMACaddressintheframe,itissimpletogenerateandselecttheforwardingportalgorithmdirectlybasedontheMACaddress,whichisconvenientforASICimplementation,sotheforwardingspeedisextremelyhigh.Buttheworkingmechanismoftheswitchalsobringssomeproblems.

1.Loop:Accordingtoswitchaddresslearningandstationtableestablishmentalgorithm,loopsarenotallowedbetweenswitches.Oncethereisaloop,thespanningtreealgorithmmustbestartedtoblocktheportthatgeneratestheloop.Therouter'sroutingprotocoldoesnothavethisproblem.Therecanbemultiplepathsbetweenrouterstobalancetheloadandimprovereliability.

2.Loadconcentration:Therecanonlybeonepathbetweenswitches,sothatinformationisconcentratedononecommunicationlink,anddynamicdistributionisnotpossibletobalancetheload.Therouter'sroutingprotocolalgorithmcanavoidthis.TheOSPFroutingprotocolalgorithmcannotonlygeneratemultipleroutes,butalsoselectdifferentoptimalroutesfordifferentnetworkapplications.

3.Broadcastcontrol:Theswitchcanonlyreducetheconflictdomain,butnotthebroadcastdomain.Theentireswitchednetworkisalargebroadcastdomain,andbroadcastmessagesarescatteredthroughouttheswitchednetwork.Theroutercanisolatethebroadcastdomain,andbroadcastpacketscannotcontinuetobebroadcastthroughtherouter.

4.Subnetting:TheswitchcanonlyrecognizetheMACaddress.TheMACaddressisaphysicaladdressandusesaflataddressstructure,sothesubnetcannotbedividedaccordingtotheMACaddress.TherouterrecognizestheIPaddress.TheIPaddressisassignedbythenetworkadministrator.ItisalogicaladdressandtheIPaddresshasahierarchicalstructure.Itisdividedintoanetworknumberandahostnumber.Itcanbeeasilyusedtodividesubnets.ThemainfunctionoftherouteristoConnecttodifferentnetworks.

5.Confidentialityissue:AlthoughtheswitchcanalsofiltertheframebasedonthesourceMACaddress,destinationMACaddressandothercontentoftheframe,therouterimplementsthemessagebasedonthesourceIPaddress,destinationIPaddress,TCPportaddressandothercontentofthemessage.Filteringismoreintuitiveandconvenient.

Manualexchange

Thehistoryofelectricalsignalexchangeshouldbetracedbacktotheearlydaysoftelephone.Whenthetelephonewasinvented,onlyawirethatwaslongenough,plustwophonesattheend,couldenabletwopeoplefaraparttohaveavoiceconversation.

Asthenumberoftelephonesincreases,itisimpossibleforustohavealinebetweeneverytwotelephonesifeveryonewhohasatelephonecancommunicatewitheachother.Sopeoplesetupatelephoneexchange,andeachtelephoneuserconnectsalinetoalargecircuitboardinthetelephoneexchange.WhenAwantstotalktoB,heaskstheoperatorofthetelephoneexchangetoconnecttoB'sphone.Theoperatorusesawire,oneendisinsertedintotheholeofAtoconnecttothecircuitboard,andtheotherendisinsertedintotheholeofB.Thisis"connection",whichisequivalenttotemporarilypullingatelephonelineforAandB.Atthistime,bothpartiescanCalled.Whenthecallisover,theoperatorremovesthewire,whichiscalled"disconnection".Thewholeprocessis"manualexchange",whichisactuallyaprocessof"closingtheswitch"and"disconnectingtheswitch".Therefore,translating"exchange"into"switch"istechnicallyeasiertounderstand.

Electronicroutecontrol

Theefficiencyofmanualswitchingistoolowtomeettheneedsoflarge-scaletelephonedeployment.Withthedevelopmentofsemiconductortechnologyandthematurityofswitchingcircuittechnology,peoplehavefoundthatelectronictechnologycanbeusedtoreplacemanualswitching.Aslongasthetelephoneterminalusersendsaseriesofelectricalsignalstotheelectronicdevice,theelectronicdevicecanconnectthecircuitoftherequestingpartyandtherequestedpartyaccordingtoapresetprocedure,andmonopolizethecircuit,andwillnotshareitwithathirdparty(ofcourse,Duetodesignflaws,theremaybesituationswheremultiplepeoplesharethecircuit,whichiscommonlyknownas"serialline").Thistypeofexchangeiscalled"program-controlledexchange".Andthiskindofequipmentisalsocalled"program-controlledswitchboard."

Asthetechnologyofprogram-controlledswitchinghasbeenmonopolizedbydevelopedcountriesforalongtime,andtheequipmentisexpensive,thetelephonepenetrationrateinmycountryhasnotbeenhigh.Withtheindependentdevelopmentofprogram-controlledswitchesbycompaniessuchasHuaweiandZTE,telephoneshaverapidlybecomepopularinmycountry.

Thecommonlyusedcommunicationprotocolforvoiceprogram-controlledswitchesisSignallingSystemNo.7

Comparedwithhubs

1.FromtheperspectiveoftheOSIarchitecture,thehubbelongstothefirstlayerofphysicallayerequipment,andtheswitchbelongstothesecondlayerofOSIdatalinklayerequipment.Inotherwords,thehubonlyplaystheroleofsynchronizing,amplifyingandshapingthedatatransmission.Itcannoteffectivelyprocesstheshortframesandfragmentsinthedatatransmission,andcannotguaranteetheintegrityandcorrectnessofthedatatransmission;buttheswitchcannotonlySynchronize,amplifyandreshapedatatransmission,andcanfiltershortframes,fragments,etc.

2.Fromtheperspectiveofworkingmode,thehubisabroadcastmode,whichmeansthatwhenacertainportofthehubisworking,allotherportscanlistentoinformation,whichispronetobroadcaststorms.Whenthenetworkislarge,thenetworkperformancewillbegreatlyaffected.;Theswitchcanavoidthisphenomenon.Whentheswitchisworking,onlytherequestingportandthedestinationportrespondtoeachotherwithoutaffectingotherports.Therefore,theswitchcanisolatetheconflictdomainandeffectivelysuppressthegenerationofbroadcaststorms.

3.Fromtheperspectiveofbandwidth,nomatterhowmanyportsthehubhas,allportsshareabandwidth.Onlytwoportscantransmitdataatthesametime,andotherportscanonlywait.Atthesametime,thehubcanonlyworkinhalf-duplexmode;Fortheswitch,eachporthasanexclusivebandwidth.Whentwoportswork,itdoesnotaffecttheworkofotherports.Atthesametime,theswitchcanworknotonlyinhalf-duplexmodebutalsoinfull-duplexmode.

Exchangemethod

Theswitchexchangesinthefollowingthreeways:

1)Straight-through:

Thestraight-throughEthernetswitchcanbeunderstoodasalinematrixtelephoneswitchthatcrossesverticallyandhorizontallybetweeneachport.Whenitdetectsadatapacketattheinputport,itcheckstheheaderofthepacket,obtainsthedestinationaddressofthepacket,activatestheinternaldynamiclookuptabletoconvertitintothecorrespondingoutputport,connectsattheintersectionofinputandoutput,andpassesthedatapacketdirectlytoThecorrespondingportrealizestheswitchingfunction.Sincenostorageisrequired,thedelayisverysmallandtheexchangeisveryfast,whichisitsadvantage.ItsdisadvantageisthatbecausethecontentofthedatapacketisnotsavedbytheEthernetswitch,itcannotcheckwhetherthetransmitteddatapacketiswrong,anditcannotprovideerrordetectioncapabilities.Becausethereisnobuffer,input/outputportswithdifferentspeedscannotbedirectlyconnected,andpacketsareeasilylost.

2)Store-and-forward:

Store-and-forwardisthemostwidelyusedmethodinthefieldofcomputernetworks.Itstoresthedatapacketoftheinputportfirst,andthenperformsCRC(cyclicredundancycheck)check.Afterprocessingtheerrorpacket,ittakesoutthedestinationaddressofthedatapacket,andconvertsitintotheoutputportthroughalookuptabletosendoutthepacket.Becauseofthis,thestore-and-forwardmethodhasalargedelayindataprocessing,whichisitsshortcoming,butitcanperformerrordetectiononthedatapacketsenteringtheswitchandeffectivelyimprovethenetworkperformance.Itisespeciallyimportantthatitcansupporttheconversionbetweenportsofdifferentspeedsandmaintainthecooperationbetweenhigh-speedportsandlow-speedports.

3)Fragmentationisolation:

Thisisasolutionbetweentheformertwo.Itcheckswhetherthelengthofthedatapacketis64bytes,ifitislessthan64bytes,itmeansitisafakepacket,andthendiscardsthepacket;ifitisgreaterthan64bytes,thepacketissent.Thismethodalsodoesnotprovidedataverification.Itsdataprocessingspeedisfasterthanstore-and-forward,butslowerthanstraight-through.

Portswitching

Portswitchingtechnologyfirstappearedinslot-typehubs.ThebackplaneofsuchhubsisusuallydividedintomultipleEthernetsegments(eachnetworksegmentisoneBroadcastdomain),withoutbridgeorroutingconnection,thenetworksarenotconnectedtoeachother.AftertheEthernetmainmoduleisinserted,itisusuallyallocatedtoanetworksegmentofabackplane.PortswitchingisusedtodistributeandbalancetheportsoftheEthernetmoduleamongmultiplenetworksegmentsofthebackplane.Accordingtothedegreeofsupport,portswitchingcanalsobesubdividedinto:

·Moduleswitching:Theentiremoduleismigratedtothenetworksegment.

·Portgroupexchange:Usuallytheportsonthemodulearedividedintoseveralgroups,andeachgroupofportsallowsnetworksegmentmigration.

·Port-levelswitching:supporteachporttomigratebetweendifferentnetworksegments.ThisswitchingtechnologyisbasedonthefirstlayerofOSIandhastheadvantagesofflexibilityandloadbalancingcapabilities.Ifconfiguredproperly,itcanbefault-toleranttoacertainextent,butitdoesnotchangethecharacteristicsofthesharedtransmissionmedium,andthuscannotbecalledatrueexchange.

Frameswitching

FrameswitchingisthemostwidelyusedLANswitchingtechnology.Itprovidesamechanismforparalleltransmissionthroughmicro-segmentationoftraditionaltransmissionmediatoreduceconflictareasandobtainHighbandwidth.Generallyspeaking,theimplementationtechnologyofeachcompany'sproductswillbedifferent,buttheprocessingmethodsfornetworkframesaregenerallyasfollows:

Straight-throughswitching:Provideswire-speedprocessingcapabilities,andtheswitchcanonlyaccessthenetworkThefirst14bytesoftheframewilltransmitthenetworkframetothecorrespondingport.

Storeandforward:Checkandcontrolerrorsbyreadingnetworkframes.

Theswitchingspeedoftheformermethodisveryfast,butitlacksmoreadvancedcontrolofnetworkframes,lacksintelligenceandsecurity,andcannotsupporttheswitchingofportswithdifferentrates.Therefore,variousmanufacturersfocusonthelattertechnology.

Somemanufacturersevendecomposethenetworkframeanddividetheframeintofixed-sizecells.Thecellprocessingisextremelyeasytoimplementwithhardware,andtheprocessingspeedisfast.Atthesametime,itcancompleteadvancedcontrolfunctions(suchastheUnitedStates).MADGE'sLEThub)suchasprioritycontrol.

Cellexchange

ATMtechnologyusesafixed-length53-bytecellexchange.Sincethelengthisfixed,itiseasytoimplementinhardware.ATMusesdedicatednon-differentiatedconnectionsandrunsinparallel.Multiplenodescanbeestablishedatthesametimethroughaswitch,butitwillnotaffectthecommunicationcapabilitiesbetweeneachnode.ATMalsoallowsmultiplevirtuallinkstobeestablishedbetweenthesourcenodeandthetargetnodetoensuresufficientbandwidthandfaulttolerance.ATMusesstatisticaltime-divisioncircuitsformultiplexing,whichcangreatlyimprovechannelutilization.ThebandwidthofATMcanreach25M,155M,622MandevenseveralGbtransmissioncapacity.Butwiththeemergenceof10GigabitEthernet,ATMtechnology,whichoncerepresentedthefuturedirectionofnetworkandcommunicationtechnologydevelopment,begantograduallyloseitsmeaning.

Thedifferencebetweenthenumberoflayers

Layer2switch,thedifferencebetweenaLayer3switchandaLayer4switch

Layer2switching

Thedevelopmentofthetwo-layerswitchingtechnologyisrelativelymature.Thetwo-layerswitchisadatalinklayerdevice.ItcanidentifytheMACaddressinformationinthedatapacket,forwarditaccordingtotheMACaddress,andrecordtheseMACaddressesandthecorrespondingportsintheInanaddresstablewithinoneself.

Thespecificworkflowisasfollows:

1)Whentheswitchreceivesadatapacketfromacertainport,itfirstreadsthesourceMACaddressinthepacketheader,sothatitknowsthesourceWhichportthemachinewiththeMACaddressisconnectedto;

2)ThenreadthedestinationMACaddressintheheader,andlookupthecorrespondingportintheaddresstable;

3)IfthereisaportcorrespondingtothedestinationMACaddressinthetable,copythedatapacketdirectlytothisport;

4)Ifthecorrespondingportisnotfoundinthetable,broadcastthedatapackettoallportsAbove,whenthedestinationmachinerespondstothesourcemachine,theswitchcanalsorecordwhichportthedestinationMACaddresscorrespondsto,anditisnolongernecessarytobroadcasttoallportswhentransmittingdatanexttime.Thisprocessisrepeatedcontinuously,andtheMACaddressinformationoftheentirenetworkcanbelearned.ThisishowtheLayer2switchestablishesandmaintainsitsownaddresstable.

FromtheworkingprincipleoftheLayer2switch,thefollowingthreepointscanbeinferred:

1)Sincetheswitchexchangesdataofmostportsatthesametime,thisrequiresawideswitchingbusbandwidth,IftheL2switchhasNports,thebandwidthofeachportisM,andthebusbandwidthoftheswitchexceedsN×M,thentheswitchcanrealizewire-speedswitching

2)Learnthemachine'sMACaddress,writtenintotheaddresstable,thesizeoftheaddresstable(generallytworepresentations:oneisBEFFERRAM,theotheristhevalueoftheMACtableentry),thesizeoftheaddresstableaffectstheaccesscapacityoftheswitch

3)AnotheristhatLayer2switchesgenerallycontainASIC(ApplicationSpecificIntegratedCircuit)chipsspeciallyusedtoprocessdatapacketforwarding,sotheforwardingspeedcanbeveryfast.AseachmanufacturerusesdifferentASICs,itdirectlyaffectsproductperformance.

TheabovethreepointsarealsothemaintechnicalparametersforjudgingtheperformanceofLayer2andLayer3switches.Pleasepayattentiontocomparisonwhenconsideringequipmentselection.

Three-layerswitch

Let’stakealookattheworkingprocessofthree-layerswitchthroughasimplenetwork.

DeviceAusingIP------------------------Layer3switch------------------------DeviceBusingIP

Forexample,ifAwantstosenddatatoB,knowingthedestinationIP,thenAusesthesubnetmasktoobtainthenetworkaddress,DeterminewhetherthedestinationIPisinthesamenetworksegmentasyourself.Ifyouareonthesamenetworksegment,butdon’tknowtheMACaddressrequiredtoforwardthedata,AsendsanARPrequest,BreturnsitsMACaddress,AusesthisMACtoencapsulatethedatapacketandsendsittotheswitch,andtheswitchusestheLayer2switchingmoduletofindMACaddresstable,forwardthedatapackettothecorrespondingport.

IfthedestinationIPaddressisnotinthesamenetworksegment,thenAneedstocommunicatewithB.IfthereisnocorrespondingMACaddressentryintheflowcacheentry,thefirstnormaldatapacketwillbesenttoafault.Provincialgateway.Thisdefaultgatewayisgenerallysetintheoperatingsystem.TheIPofthisdefaultgatewaycorrespondstothethirdlayerroutingmodule,sofordatathatisnotinthesamesubnet,thedefaultgatewayisthefirsttobeplacedintheMACtableTheMACaddress(completedbythesourcehostA);thenthethree-layermodulereceivesthedatapacket,andqueriestheroutingtabletodeterminetheroutetoB.Anewframeheaderwillbeconstructed,inwhichtheMACaddressofthedefaultgatewayisThesourceMACaddress,withtheMACaddressofhostBasthedestinationMACaddress.Throughacertainrecognitiontriggermechanism,establishthecorrespondingrelationshipbetweentheMACaddressesandforwardingportsofhostAandB,andrecordthemintotheflowcacheentrytable,andthenthedatafromAtoB(thethree-layerswitchmustconfirmthatitisfromAtoBinsteadofFordatatoC,theIPaddressintheframemustberead.),itisdirectlyhandedovertothelayer2switchingmoduleforcompletion.Thisisusuallyreferredtoasonerouteandmultipleforwarding.

Theaboveisabriefsummaryoftheworkingprocessofthethree-layerswitch.Thecharacteristicsofthethree-layerswitchcanbeseen:

1)High-speeddataforwardingisrealizedbythecombinationofhardware.ThisisnotasimplesuperpositionofLayer2switchesandrouters.Layer3routingmodulesaredirectlysuperimposedonthehigh-speedbackplanebusofLayer2switching,breakingthroughtheinterfaceratelimitoftraditionalrouters,andtheratecanreachdozensofGbit/s.Countingthebackplanebandwidth,thesearetwoimportantparametersfortheperformanceoftheLayer3switch.

2)Theconciseroutingsoftwaresimplifiestheroutingprocess.Mostofthedataforwarding,exceptforthenecessaryrouting,ishandledbytheroutingsoftware,anditisforwardedathighspeedbytheLayer2module.Mostoftheroutingsoftwareisprocessedandoptimizedsoftware,notsimplycopyingthesoftwareintherouter.

ThechoiceofLayer2andLayer3switches

Layer2switchesareusedforsmalllocalareanetworks.Needlesstosay,inasmalllocalareanetwork,broadcastpacketshavelittleeffect.Thefastswitchingfunction,multipleaccessportsandlowcostofthetwo-layerswitchprovideaverycompletesolutionforsmallnetworkusers.

Theadvantageofathree-layerswitchisthatithasrichinterfacetypes,supportspowerfulthree-layerfunctions,andpowerfulroutingcapabilities.Itissuitableforroutingbetweenlargenetworks.Itsadvantageliesinselectingthebestrouteandloadsharing.Linkbackupandexchangeofroutinginformationwithothernetworks,etc.routershavefunctions.

ThemostimportantfunctionoftheLayer3switchistospeedupthefastforwardingofdatawithinalargelocalareanetwork.Theadditionoftheroutingfunctionalsoservesthispurpose.IfalargenetworkisdividedintosmallLANsaccordingtofactorssuchasdepartments,regions,etc.,thiswillleadtoalargenumberofInternetaccesses,whichcannotbeachievedbysimplyusingLayer2switches.Forexample,simplyusingrouters,duetothelimitednumberofinterfacesandTheroutingandforwardingspeedisslow,whichwilllimitthenetworkspeedandnetworkscale.Theuseofafastforwardingthree-layerswitchwithroutingfunctionbecomesthefirstchoice.

Generallyspeaking,inanetworkwithlargeinternalnetworkdatatrafficandfastforwardingandresponse,ifallthethree-layerswitchesdothiswork,thethree-layerswitcheswillbeoverloadedandtheresponsespeedwillbeaffected.Itisagoodnetworkingstrategytogivefullplaytotheadvantagesofdifferentdevicestocompletetheroutingbetweenthenetworksbyrouters.Ofcourse,thepremiseisthatthecustomer’spocketsareverybulging,otherwiseitisbettertogiveprioritytothethree-layerswitch.ItalsoservesasInternetinterconnection.

Layer4switching

Asimpledefinitionoflayer4switchingis:itisafunctionthatdeterminestransmissionnotonlybasedonMACaddress(layer2bridge)orsource/DestinationIPaddress(layer3routing),andportnumberaccordingtoTCP/UDP(layer4)application.ThefourthlayerswitchingfunctionislikeavirtualIP,pointingtoaphysicalserver.Thebusinessittransmitsissubjecttovariousprotocols,suchasHTTP,FTP,NFS,Telnetorotherprotocols.Theseservicesrequirecomplexloadbalancingalgorithmsbasedonphysicalservers.

IntheIPworld,theservicetypeisdeterminedbytheterminalTCPorUDPportaddress,andtheapplicationintervalinthefourthlayerexchangeisdeterminedbythesourceandterminalIPaddresses,TCPandUDPports.Inthefourthlayerofexchange,avirtualIPaddress(VIP)issetupforeachservergroupforsearching,andeachgroupofserverssupportsacertainapplication.Eachapplicationserveraddressstoredinthedomainnameserver(DNS)isaVIP,notarealserveraddress.Whenauserappliesforanapplication,aVIPconnectionrequest(suchasaTCPSYNpacket)withatargetservergroupissenttotheserverswitch.Theserverswitchselectsthebestserverinthegroup,replacestheVIPintheterminaladdresswiththeIPoftheactualserver,andtransmitstheconnectionrequesttotheserver.Inthisway,allpacketsinthesamesectionaremappedbytheserverswitchandtransmittedbetweentheuserandthesameserver.

Features:

ThefourthlayeroftheOSImodelisthetransportlayer.Thetransportlayerisresponsibleforend-to-endcommunication,thatis,coordinatedcommunicationbetweennetworksourceandtargetsystems.IntheIPprotocolstack,thisistheprotocollayerwhereTCP(atransmissionprotocol)andUDP(userdatapacketprotocol)arelocated.

Inthefourthlayer,TCPandUDPheaderscontainportnumbers,whichcanuniquelydistinguishwhichapplicationprotocols(suchasHTTP,FTP,etc.)eachdatapacketcontains.Theendpointsystemusesthisinformationtodistinguishthedatainthepacket,especiallytheportnumbersothatareceivingcomputersystemcandeterminethetypeofIPpacketitreceives,andhanditovertotheappropriatehigh-levelsoftware.ThecombinationofportnumberanddeviceIPaddressisusuallycalled"socket".Portnumbersbetween1and255arereserved,andtheyarecalled"familiar"ports,thatistosay,theseportnumbersarethesameinallhostTCP/IPprotocolstackimplementations.Inadditionto"familiar"ports,standardUNIXservicesareallocatedintherangeof256to1024ports,andcustomapplicationsgenerallyallocateportnumbersabove1024.ThelistofassignedportnumberscanbefoundonRFC1700"AssignedNumbers".

TheadditionalinformationprovidedbytheTCP/UDPportnumbercanbeusedbythenetworkswitch,whichisthebasisofthefourthlayerofexchange.Theswitchwiththefourthlayerfunctioncanplaytheroleofthe"virtualIP"(VIP)frontendconnectedwiththeserver.EachserverandservergroupsupportingasingleorgeneralapplicationisconfiguredwithaVIPaddress.ThisVIPaddressissentoutandregisteredonthedomainnamesystem.Whensendingaservicerequest,thefourthlayerswitchrecognizesthebeginningofasessionbydeterminingthestartofTCP.Itthenusescomplexalgorithmstodeterminethebestservertohandlethisrequest.Oncethisdecisionismade,theswitchassociatesthesessionwithaspecificIPaddressandreplacestheVIPaddressontheserverwiththerealIPaddressoftheserver.

EachLayer4switchsavesaconnectiontableassociatedwiththesourceIPaddressandsourceTCPportoftheselectedserver.Thenthefourthlayerswitchforwardstheconnectionrequesttothisserver.Allsubsequentpacketsarere-mappedandforwardedbetweentheclientandtheserveruntiltheswitchdiscoverstheconversation.Inthecaseofusingthefourthlayerofswitching,accesscanbeconnectedwithrealserverstomeetuser-definedrules,suchashavinganequalnumberofaccessesoneachserverorallocatingtransmissionstreamsaccordingtothecapacityofdifferentservers.

1)Speed

Inordertobeeffectiveinthecorporatenetwork,thefourthlayerofswitchingmustprovideperformancecomparabletothatofthethirdlayerofwire-speedrouters.Inotherwords,Layer4switchingmustoperateatfullmediaspeedonallports,evenonmultipleGigabitEthernetconnections.GigabitEthernetspeedisequivalenttoroutingatthemaximumspeedof1488000packetspersecond(assumingtheworstcase,thatis,allpacketsaretheminimumsizedefinedbythenetworkandare64byteslong).

2)Servercapacitybalancealgorithm

Accordingtothedesiredcapacitybalanceintervalsize,therearemanyalgorithmsfortheallocationofapplicationstoserversbythefourthlayerswitch,andtherearesimpledetectionloops.Thelatestconnection,detectionloopdelayorclosed-loopfeedbackfromthedetectionserveritself.Ofallthepredictions,closed-loopfeedbackprovidesthemostaccuratedetectionthatreflectstheexistingbusinessvolumeoftheserver.

3)Tablecapacity

Itshouldbenotedthattheswitchthatperformsthefourthlayerexchangeneedstohavetheabilitytodistinguishandstorealargenumberofsenttableentries.Thisisespeciallytruewhentheswitchisatthecoreofanenterprisenetwork.ManyLayer2/3switchestendtosendthesizeofthetableindirectproportiontothenumberofnetworkdevices.ForLayer4switches,thisnumbermustbemultipliedbythenumberofdifferentapplicationprotocolsandsessionsusedinthenetwork.Therefore,thesizeofthesendingtableincreasesrapidlywiththenumberofendpointdevicesandapplicationtypes.Layer4switchdesignersneedtoconsiderthisgrowthintableswhendesigningtheirproducts.Alargetablecapacityisessentialformanufacturinghigh-performanceswitchesthatsupportwire-speedtransmissionofLayer4traffic.

4)Redundancy

Thefourthlayerswitchhasthefunctionofsupportingredundanttopologystructure.Inthecaseofafault-tolerantconnectionwithadual-linknetworkcard,itispossibletoestablishacompletelyredundantsystemfromaservertothenetworkcard,linkandserverswitch.

Managementmethod

Thenetworkmanagementswitchcanbemanagedthroughthefollowingways:throughtheRS-232serialport(orparallelport)management,throughthewebbrowsermanagementandthroughthenetworkManagementsoftwaremanagement.

Serialportmanagement

Thenetworkmanagementswitchcomeswithaserialportcableforswitchmanagement.Firstplugoneendoftheserialcableintotheserialportonthebackoftheswitch,andplugtheotherendintotheserialportofanordinarycomputer.Thenpowerontheswitchandthecomputer.The"HyperTerminal"programisprovidedinbothWindows98andWindows2000.Openthe"HyperTerminal",aftersettingtheconnectionparameters,youcaninteractwiththeswitchthroughtheserialcable,asshowninFigure1.Thismethoddoesnotoccupythebandwidthoftheswitch,soitiscalled"Outofband"(Outofband).

Inthismanagementmode,theswitchprovidesamenu-drivenconsoleinterfaceorcommandlineinterface.Youcanusethe"Tab"keyorarrowkeystomovethroughthemenusandsubmenus,presstheEnterkeytoexecutethecorrespondingcommands,orusethededicatedswitchmanagementcommandsettomanagetheswitch.Switchesofdifferentbrandshavedifferentcommandsets,andevenswitchesofthesamebrandhavedifferentcommands.Usingmenucommandsismoreconvenientinoperation.

Webmanagement

ThemanagedswitchcanbemanagedthroughtheWeb(webbrowser),butanIPaddressmustbeassignedtotheswitch.ThisIPaddresshasnootherpurposeexceptforthemanagementswitch.Inthedefaultstate,theswitchdoesnothaveanIPaddress.YoumustspecifyanIPaddressthroughtheserialportorothermethodstoenablethismanagementmethod.

Whenusingawebbrowsertomanagetheswitch,theswitchisequivalenttoawebserver,butthewebpageisnotstoredintheharddisk,butintheNVRAMoftheswitch.ThewebprogramintheNVRAMcanbeupgradedthroughtheprogram.WhentheadministratorenterstheIPaddressoftheswitchinthebrowser,theswitchtransmitsthewebpagetothecomputerlikeaserver.Atthistime,itfeelslikeyouarevisitingawebsite,asshowninFigure2.Thismethodoccupiesthebandwidthoftheswitch,soitiscalled"inbandmanagement"(Inband).

Ifyouwanttomanagetheswitch,justclickthecorrespondingfunctionitemonthewebpageandchangetheswitchparametersinthetextboxordrop-downlist.Webmanagementcanbecarriedoutonthelocalareanetworkinthisway,soremotemanagementcanberealized.

Softwaremanagement

ThenetworkmanagementswitchesallfollowtheSNMPprotocol(SimpleNetworkManagementProtocol),whichisasetofnetworkequipmentmanagementspecificationsthatcomplywithinternationalstandards.AlldevicesthatfollowtheSNMPprotocolcanbemanagedthroughnetworkmanagementsoftware.YouonlyneedtoinstallasetofSNMPnetworkmanagementsoftwareonanetworkmanagementworkstation,andyoucaneasilymanagetheswitches,routers,servers,etc.onthenetworkthroughtheLAN.TheinterfaceoftheSNMPnetworkmanagementsoftwareisshowninFigure3.Itisalsoanin-bandmanagementmethod.

Themanagementofmanagedswitchescanbemanagedintheabovethreeways.Whichmethodisused?Whentheswitchisinitiallysetup,itisoftenthroughout-of-bandmanagement;aftersettingtheIPaddress,youcanusein-bandmanagement.In-bandmanagementBecausethemanagementdataistransmittedthroughapubliclyusedLAN,remotemanagementcanbeachieved,butthesecurityisnotstrong.Out-of-bandmanagementisthroughserialcommunication,anddataisonlytransferredbetweentheswitchandthemanagementmachine,sothesecurityisverystrong;however,duetothelimitationofthelengthoftheserialcable,remotemanagementcannotberealized.Sowhichmethodyouusedependsonyourrequirementsforsecurityandmanageability.

Hardwarefailure

Switchfailurescangenerallybedividedintohardwarefailuresandsoftwarefailures.Hardwarefailuresmainlyrefertothefailuresofthepowersupply,backplane,modules,andportsoftheswitch,whichcanbedividedintothefollowingcategories.

Powerfailure

Thepowersupplyisdamagedorthefanstopsduetounstableexternalpowersupply,ortheagingofthepowerlineorlightningstrikes,etc.,sothatthefactorycannotworknormally.

Duetothepowersupply,otherpartsinthemachinearedamagedoften.IfthePowERindicatoronthepanelisgreen,itmeansitisnormal:iftheindicatorisoff,itmeansthattheswitchisnotsupplyingpowernormally.Thistypeofproblemiseasytofind,easytosolve,andalsotheeasiesttoprevent.Inresponsetothistypeoffailure,theexternalpowersupplyshouldbedonefirst,generallybyintroducinganindependentpowerlinetoprovideanindependentpowersupply,andaddingavoltagestabilizertoavoidtransienthighorlowvoltage.Ifconditionspermit,youcanaddanuninterruptiblepowersupplytoensurethenormalpowersupplyoftheswitch.Someprovidevoltagestabilizationfunctions,andsomedonot.Payattentionwhenchoosing.Setupprofessionallightningprotectionmeasuresintheequipmentroomtoavoidlightningdamagetotheswitch.Therearemanyprofessionalcompaniesthatdolightningprotectionprojects,whichcanbeconsideredwhenimplementingnetworkcabling.

Portfailure

Thisisthemostcommonhardwarefailure.WhetheritisanopticalfiberportoratwistedpairRJ45port,youmustbecarefulwhenpluggingandunpluggingtheconnector.Iftheopticalfiberplugisaccidentallysoiled,itmaycausepollutionoftheopticalfiberportandfailureofnormalcommunication.Weoftenseethatmanypeoplelikepluggingandunpluggingtheconnectorunderpower.Theoreticallyspeaking,itispossible,butthisalsounintentionallyincreasesthefailurerateoftheport.

Inaddition,carelesshandlingmayalsocausephysicaldamagetotheport.Ifthesizeoftheplug-inpurchasedistoolarge,electricitywilleasilydamagetheportwhenitisinsertedintotheswitch.Inaddition,ifasectionofthetwistedpairconnectedtotheportisexposedtotheoutdoors,ifthecableisstruckbylightning,theconnectedswitchportwillbedamaged,orevenmoreunpredictabledamagewillbecaused.Ingeneral,aportfailureisthatoneorseveralportsaredamaged.Therefore,aftertroubleshootingthecomputerconnectedtotheport,youcandeterminewhetheritisdamagedbyreplacingtheconnectedport.Incaseofthiskindoffailure,youcantrytocleantheportwithanalcoholcottonballafterthepoweristurnedoff.Iftheportisindeeddamaged,youcanonlyreplacetheport.

Modulefailure

Theswitchiscomposedofmanymodules,suchasstackingmodules,managementmodules(controlmodules),andexpansionmodules.Theprobabilityoffailureofthesemodulesisverysmall,butonceaproblemoccurs,itwillsufferhugeeconomiclosses.Ifthemoduleisinsertedorremovedcarelessly,ortheswitchisbumpedwhenmoving,orthepowersupplyisunstable,thismaycausesuchfailures.

Backplanefailure

Allmodulesoftheswitcharepluggedintothebackplane.Iftheenvironmentishumid,thecircuitboardisdampandshort-circuited,orthecomponentsaredamagedduetohightemperature,lightningstrikesandotherfactors,thecircuitboardwillnotworkproperly.Forexample:Poorheatdissipationperformanceortoohighambienttemperaturecausesthetemperatureinsidethemachinetorise,causingthecomponentstoburnout.Inthecaseofnormalpowersupplyfromtheexternalpowersupply,iftheinternalmodulesoftheswitchcannotworknormally,itmaybethatthebackplaneisbroken.Inthiscase,eventheelectricalmaintenanceengineerhasnothingtodo.Theonlywayistoreplacethebackplane.Boardup.

Cablefailure

Infact,thistypeoffailureistheoreticallynotafailureoftheswitchitself,butinactualuse,cablefailureoftencausestheswitchsystemorporttonotworkproperly,Sothistypeoffailureisalsoclassifiedasaswitchhardwarefailure.Forexample,theconnectorsarenotconnectedtightly,theorderofthecablesiswrongornotstandardizedwhenthecablesaremade,thecableshouldbeconnectedwithacrossovercablebutastraightcableisused,thetwoopticalfibersintheopticalcableareconnectedinastaggeredmanner,andthewronglineconnectioncausesanetworkloop.Wait.

Switchtesttechnology

Nowadays,switchesputforwardnewrequirementsforswitchperformancebasedonapplicationrequirements.Therehavebeennewdevelopmentsincomprehensivenetworkservices,security,andintelligence.Protocoltestingisabasicswitchtestingtechnology.Thenetworkprotocolistoimprovetheefficiencyoftestingandtheeffectivenessofcommunicationtoensuretherulesofcommunication.Intheeraofincreasingnetworkcommunication,networkprotocolsarealsoindispensable.Thebasicrequirementsofnetworkprotocolsarecorrectfunctions,goodinteroperabilityandsuperiorperformance.Theinitialprototypeofprotocoltestingissoftwaretesting,andthemaincategoriesareblackboxtesting,whiteboxtestingandgrayboxtesting.Nowbrieflyexplainthebasicprinciplesofblackboxtesting,usingastimulustomakeitactontheobjectundertest,usingtheresponseoftheobjectundertest,withoutconsideringthespecificstructureandprincipleoftheobjectundertest,wecanstillgetAtransferfunction,thistransferfunctionisthedataweneed.Usingthisprinciple,thetestoftheswitchintheEthernetcanalsobecarriedout.Sendapieceofdataandinformationtotheswitchandanalyzethereturnedinformationtodeterminethefailureoftheswitch.

Developmentprospects

Withtherapiddevelopmentofcloudcomputingandvirtualizationtechnologies,theintegrationofdatacenterserviceshasputforwardhigherrequirementsfortheperformance,functions,andreliabilityofswitches..However,sincethedatacenterswitchcancarryvariousservices,itprovidesabetterguaranteefordatatransmission.Inthefuture,datacenterswitcheswillcarrymoreservicesinthefuture,whichwillhavegoodscalabilityforthedevelopmentoffuturenetworks.Therefore,itisbelievedthatfortheestablishmentoffuturedatacenters,datacenterswitcheswilldevelopwiththedevelopmentofthetimesanddevelopswitcheswithhigherperformance,stabilityandnewertechnologiesinresponsetotheneedsofthenetwork.Nowthatwehaveenteredthedataage,Ibelievethatdatacenterswitcheswilldefinitelyshowtheirambitions.

Theworldisadvancing,scienceandtechnologyaredeveloping,andtheInternetisconstantlyaccelerating.Fromtheadventofthefirstnetworkcard,tothecurrentuniversalGigabitEthernetcard,10Gigabitnetworkcard,andevenmanysuper10Gigabitnetworkcards.Itindicatesthattheworldisundergoingearth-shakingchanges,anddatatrafficisconstantlyincreasing.Traditionalswitchescannolongermeettheincreasinglycomplexnetworksandhugetraffic.Inordertobetterbearvariousservicessuchasvideo,voice,andfiles.Needhigh-speedhardwareandanewgenerationofswitchingsystemstohandletheincreasingdatatraffic.Withtherapiddevelopmentofcloudcomputing,theestablishmentofdatacenterswillbringgreaterchallenges,andtheperformanceandbackplanebandwidthrequirementsofswitcheswillalsobehigher.Thedatacenterswitchwasborninthisenvironmentandtookoverthetraditionalswitchworkinthedatacenter.Provideshigherreliability,morestableperformanceandgreaterthroughput.Therearealsonewertechnologiestosolvecomplexnetworks.

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