routing

Concept

1.Routingreferstotheprocessinwhicharouterreceivesadatapacketfromoneinterface,directsitaccordingtothedestinationaddressofthedatapacket,andforwardsittoanotherinterface.Routingisoftencontrastedwithbridging,whichseemstothecarelesspersontoaccomplishthesamething.Themaindifferencebetweenthemisthatbridgingoccursatthesecondlayer(datalinklayer)oftheOSIreferencemodel,whileroutingoccursatthethirdlayer(networklayer).Thisdifferencemakesthetwousedifferentinformationintheprocessoftransmittinginformation,soastocompletetheirtasksindifferentways.

Thetopicofroutinghasalreadyappearedinthecomputerworld,butitwasnotuntilthemid-1980sthatitachievedcommercialsuccess.ThemainreasonisthattheInternetwasgenerallyverysimpleinthe1970s,anditbecamemorecommonafterthedevelopmentoflarge-scalenetworks.

2.Engineeringterminology.Referstoroadconditions,includingroadwidth,depth,directionandotherinformation.

Principlealgorithm

Routingworkincludestwobasicactions:

1,determinethebestpath

2,transmitthroughthenetworkInformation

Intheprocessofrouting,thelatterisalsocalled(data)exchange.Theexchangeisrelativelysimple,andtheselectionpathiscomplicated.

Pathselection

Metricisthemeasurementstandardusedbyroutingalgorithmtodeterminethebestpathtothedestination,suchaspathlength.Tohelprouteselection,theroutingalgorithminitializesandmaintainsaroutingtablecontainingpathinformation.Thepathinformationvariesaccordingtotheroutingalgorithmused.

Theroutingalgorithmfillstheroutingtablebasedonalotofinformation.Thedestination/nexthopaddresspairinformstherouterthatthebestwaytoreachthedestinationistosendthepackettotherouterrepresentingthe“nexthop”.Whentherouterreceivesapacket,itchecksitsdestinationaddressandtriesto“dropthisaddress”withthedestinationaddress.Onejump"islinked.Thefollowingtableisanexampleofadestination/nexthoproutingtable.Theroutingtablemayalsoincludeotherinformation.Theroutingtablecomparesmetricstodeterminethebestpath.Thesemetricsvaryaccordingtotheroutingalgorithmused.Routerscommunicatewitheachotherandmaintaintheirroutingtablesbyexchangingroutinginformation.Theroutingupdateinformationusuallycontainsallorpartoftheroutingtable.Byanalyzingtheroutingupdateinformationfromotherrouters,theroutercanbuildanetworktopologymap.Anotherinformationsentbetweenroutersislinkstatebroadcastinformation,whichinformsotherroutersofthelinkstateofthesender.Thelinkinformationisusedtobuildacompletetopologymapsothattheroutercandeterminethebestpath.

Exchangealgorithm

Theexchangealgorithmisrelativelysimpleandisthesameformostroutingprotocols.Inmostcases,ahostdecidestosenddatatoanotherhost.Afterobtainingtherouter'saddressinsomeways,thesourcehostsendsadatapacketpointingtotherouter'sphysical(MAC)address,anditsprotocoladdresspointstothedestinationhost.

Aftercheckingthedestinationprotocoladdressofthedatapacket,therouterdetermineswhetheritknowshowtoforwardthepacket.Iftherouterdoesnotknowhowtoforwardit,itusuallydiscardsit.Iftherouterknowshowtoforward,itchangesthedestinationphysicaladdresstothenexthopphysicaladdressandsendsittoit.Thenexthopmaybethefinaldestinationhost,ifitisnot,usuallyanotherrouter,itwillperformthesamesteps.Whenapacketflowsinthenetwork,itsphysicaladdressischanging,butitsprotocoladdressisalwaysthesame.

ISOdefinestheterminologyusedtodescribethelayeringofthisprocess.Inthisterminology,anetworkdevicethatdoesnothavetheabilitytoforwardpacketsiscalledanendsystem(ES--endsystem),andonethathasthiscapabilityiscalledanintermediatesystem(IS--intermediatesystem).ISisfurtherdividedintointradomainIS(intradomainIS)thatcancommunicatewithinroutingdomainsandinterdomainIS(interdomainIS)thatcancommunicatebothwithinroutingdomainsandbetweendomains.Theroutingdomainisusuallyconsideredtobeapartofthenetworkunderunifiedmanagement,whichcomplieswithaspecificsetofmanagementrules,alsoknownasanautonomoussystem(autonomoussystem).Insomeprotocols,intra-domainroutingprotocolscanstillbeusedtoexchangedatawithinandbetweenintervals.

Designgoals

Routingalgorithmscanbedistinguishedbasedonmultiplecharacteristics.First,thespecificgoalsofthealgorithmdesigneraffecttheoperationoftheroutingprotocol;secondly,therearemultipleroutingalgorithms,andeachalgorithmhasadifferentimpactonthenetworkandrouterresources;finally,theroutingalgorithmusesmultiplemetrics,whichaffectthemostCalculationofthebestpath.Thecharacteristicsoftheseroutingalgorithmsareanalyzedbelow.

Routingalgorithmsusuallyhaveoneormoreofthefollowingdesigngoals:

Optimization

referstotheabilityofroutingalgorithmstoselectthebestpath,basedonthevalueofmetricandWeighttocalculate.Forexample,aroutingalgorithmmayusehopcountanddelay,buttheweightofdelaymaybelarger.Ofcourse,theroutingprotocolmuststrictlydefinethealgorithmforcalculatingthemetric.

Efficientandsimple

Itcanalsobedesignedtobeassimpleaspossible.Inotherwords,routingprotocolsmustprovidetheirfunctionsefficientlyandminimizesoftwareandapplicationoverhead.Efficientisespeciallyimportantwhenthesoftwarethatimplementstheroutingalgorithmmustrunonacomputerwithlimitedphysicalresources.

Stable

Theroutingalgorithmmustbestable,thatis,itmustbeabletoprocessnormallyintheeventofabnormalorunforeseenevents,suchashardwarefailure,highload,andincorrectimplementation.Becauseroutersarelocatedattheconnectionpointofthenetwork,theycancausemajorproblemswhentheyfail.Thebestroutingalgorithmsareusuallythosethathavepassedthetestoftimeandprovedtobestableundervariousnetworkconditions.

Quickaggregation

Aggregationistheprocessbywhichallroutersagreeonthebestpath.Whenanetworkeventcausesthepathtobebrokenorunavailable,therouterdistributesroutingupdateinformationthroughthenetwork,promptingtherecalculationofthebestpath,andfinallyreachinganagreementamongallrouters.Routingalgorithmsthatconvergeslowlymaycauseroutingloopsornetworkinterruptions.

Intheroutingringinthefigurebelow(Figure1),apacketarrivesatrouter1attimet1,router1hasbeenupdatedandknowsthatthebestpathtothedestinationisrouter2asthenexthop,soThepacketisforwardedtorouter2.Butrouter2hasnotbeenupdatedyet.Itthinksthatthebestnexthopisrouter1,soitsendsthepacketbacktorouter1.Asaresult,thepacketpassesbackandforthbetweenthetworoutersuntilrouter2receivesroutingupdateinformationorthepacketexceedsLifetime.

Flexible

Thatis,theyshouldquicklyandaccuratelyadapttovariousnetworkenvironments.Forexample,supposethatacertainnetworksegmentisbroken.Whentheproblemisknown,manyroutingalgorithmswillquicklyselectthenextbestpathforthepaththatusuallyusesthenetworksegment.Theroutingalgorithmcanbedesignedtoadapttothenetworkbandwidth,routerqueuesizeandnetworkdelay.

Algorithmtype

Thedifferencesbetweenroutingalgorithmsinclude:

Staticalgorithm

Staticroutingalgorithmcanhardlyberegardedasanalgorithm.Itisjustatablemappingestablishedbythenetworkmanagerbeforestartingrouting.Thesemappingsthemselvesdonotchangeunlessthenetworkmanagerchangesthem.Algorithmsthatusestaticroutingareeasiertodesignandworkwellinnetworkswherenetworkcommunicationispredictableandsimple.

Sincethestaticroutingsystemcannotrespondtonetworkchanges,itisgenerallyconsideredunsuitableforlargeandvolatilenetworks.Themainroutingalgorithmsinthe1990swerealldynamicroutingalgorithms,whichadaptedtochangesinthenetworkenvironmentbyanalyzingthereceivedroutingupdateinformation.Iftheinformationindicatesthatthenetworkhaschanged,theroutingsoftwarerecalculatestherouteandsendsoutnewroutingupdates.Thisinformationinfiltratesthenetwork,promptingtheroutertorecalculateandmakecorrespondingchangestotheroutingtable.

Dynamicalgorithm

Dynamicroutingalgorithmcanbesupplementedbystaticroutingwhereappropriate.Forexample,therouteroflastresort,asthewayoutforallnon-routablepackets,ensuresthatalldatahasatleastawaytoprocess.

Pathalgorithm

Somecomplexroutingprotocolssupportmultiplepathstothesamedestination.Unlikesingle-pathalgorithms,thesemulti-pathalgorithmsallowdatatobemultiplexedonmultiplelines.Theadvantagesofmultipathalgorithmsareobvious:theycanprovidebetterthroughputandreliability.

Flatandhierarchical

Someroutingprotocolsoperateinaflatspace,whileothershaveroutinghierarchies.Inaflatroutingsystem,eachrouterisequaltoallotherrouters;inahierarchicalroutingsystem,someroutersconstitutetheroutingbackbone,anddataflowsfromnon-backbonerouterstobackbonerouters,andthentransmitsonthebackboneuntiltheyareReachthetargetarea,wheretheyreachthedestinationfromthelastbackbonerouterthroughoneormorenon-backbonerouters.

Routingsystemsareusuallydesignedwithlogicalnodegroups,calleddomains,autonomoussystems,orintervals.Inahierarchicalsystem,somerouterscancommunicatewithroutersinotherdomains,andotherscanonlycommunicatewithroutersinthedomain.Inaverylargenetwork,theremaybeotherlevels,andthemostadvancedrouterconstitutestheroutingbackbone.

Themainadvantageofhierarchicalroutingisthatitsimulatesthestructureofmostcompanies,whichcanwellsupporttheircommunications.Mostnetworkcommunicationoccursinthegroup(domain).Becausetheroutersinthedomainonlyneedtoknowotherroutersinthedomain,theirroutingalgorithmscanbesimplified,andaccordingtotheroutingalgorithmused,theamountofcommunicationforroutingupdatescanbereducedaccordingly.

Intelligent

Someroutingalgorithmsassumethatthesourcenodedeterminestheentirepath,whichisusuallycalledsourcerouting.Inthesourceroutingsystem,therouteronlyactsasastorageandforwardingdevice,unconsciouslysendingpacketstothenexthop.Otherroutingalgorithmsassumethatthehostknowsnothingaboutthepath.Inthesealgorithms,therouterdeterminesthepaththroughthenetworkbasedonitsowncalculations.Intheformersystem,thehosthastheintelligencetodeterminetheroute,whilethelatterhasthisabilityfortherouter.

Thecompromisebetweenhostintelligenceandrouterintelligenceisactuallyabalancebetweenoptimalroutingandadditionaloverhead.Hostintelligentsystemscanusuallychoosethebetterpathbecausetheyexploreallpossiblepathsbeforesendingdata,andthenselectthebestpathbasedonthespecificsystem'sdefinitionof"optimization".However,determiningthebehaviorofallpathsusuallyrequiresalotofexploratorytrafficandalongtime.

Intra-domainandinter-domain

Someroutingalgorithmsonlyworkwithinthedomain,whileothersworkbothwithinandbetweendomains.Theessenceofthesetwoalgorithmsisdifferent.Thereasonforitscomplianceisthattheoptimizedintra-domainroutingalgorithmisnotnecessaryandbecomesanoptimizedinter-domainroutingalgorithm.

Linkstateanddistancevector

Linkstatealgorithm(alsocalledshortpathfirstalgorithm)spreadsroutinginformationtoeachnodeofthenetwork,buteachrouteronlysendstheroutingtableThepartthatdescribesitsownlinkstatus.Inthedistancevectoralgorithm(alsocalledtheBellman-Fordalgorithm),eachroutersendsallorpartoftheroutingtable,butonlytoitsneighbors.Inotherwords,thelinkstatealgorithmsendslessupdateinformationeverywhere,whilethedistancevectoralgorithmonlysendsmoreupdateinformationtoneighboringrouters.

Becauselinkstatealgorithmsconvergefaster,theyhavelesstendencytogenerateroutingloopsthandistancealgorithms.Ontheotherhand,thelinkstatealgorithmrequiresmoreCPUandmemoryresources,sotheimplementationandsupportofthelinkstatealgorithmismoreexpensive.Althoughtherearedifferences,thesetwotypesofalgorithmsworkwellinmostenvironments.

Metrics

Theroutingtablecontainsinformationusedbytheswitchingsoftwaretoselectthebestpath.Buthowistheroutingtableestablished?Whatisthenatureoftheinformationtheycontain?Howdoestheroutingalgorithmdecidewhichpathisbetterbasedonthisinformation?

Routingalgorithmsusemanydifferentmetricstodeterminethebestpath.Complexroutingalgorithmscanselectroutesbasedonmultiplemetricsandcombinethemintoacompositemetric.Thecommonlyusedmetricsareasfollows:

Pathlength

Pathlengthisthemostcommonlyusedroutingmetric.Someroutingprotocolsallowthenetworkadministratortomanuallyassignavaluetoeachnetworklink.Inthiscase,thepathlengthisthesumofthecostsofeachlink.Otherroutingprotocolsdefinethenumberofhops,thatis,thenumberofnetworkproducts,suchasrouters,thatapacketmustpassonitswayfromsourcetodestination.

Reliability

Intheroutingalgorithm,itreferstothedependenceofthenetworklink(usuallydescribedbythebiterrorrate).Somenetworklinksmayfailmorethanothers.AfterthenetworkfailsSomenetworklinksmaybeeasierorfastertorepairthanothers.Anyreliabilityfactorcanbecalculatedwhenassigningareliabilityrate,usuallythenetworkadministratorassignsametricvaluetothenetworklink.

Delay

Itreferstothetimeittakesforapackettotravelfromthesourcetothedestinationthroughthenetwork.Manyfactorsaffectthedelay,includingthebandwidthoftheintermediatenetworklink,theportqueueofeachrouterpassingthrough,thecongestionlevelofallintermediatenetworklinks,andthephysicaldistance.Becauselatencyisamixtureofmanyimportantvariables,itisamorecommonlyusedandeffectivemetric.

Bandwidth

Bandwidthreferstotheavailablecirculationcapacityofthelink.Whenallotherconditionsareequal,a10MbpsEthernetlinkispreferabletoa64kbpsdedicatedline.Althoughbandwidthisthemaximumthroughputavailableforalink,routingthroughalinkwithalargerbandwidthisnotnecessarilybetterthanroutingthroughaslowerlink.Forexample,ifafastlinkisverybusy,itmaytakelongerforthepackettoreachitsdestination.

Load

Loadreferstonetworkresources,suchashowbusytherouteris.Loadcanbecalculatedinmanyways,includingCPUusageandthenumberofpacketsprocessedpersecond.Continuouslymonitoringtheseparametersitselfisalsoveryresourceintensive.

Communicationcostisanotherimportantmetric,especiallyassomecompaniesmayhavemoretodowithoperatingcoststhanperformance.Eventhoughthelinedelaymaybelonger,theywouldrathersenddatathroughtheirownlinesthanusingexpensivepubliclines.

Type

Routingisdividedintothreesources:staticrouting,dynamicrouting,anddirectrouting.

Features

Featuresofstaticrouting

Staticroutingisafixedroutemanuallyconfiguredbytheadministratorontherouter

StaticroutingAllowingprecisecontrolofroutingbehaviorreducesnetworktrafficone-wayandsimpleconfigurationstaticroutingusuallyhasthehighestprioritybecauseitsadministrativedistanceistheshortest.Staticroutingisafixedroutingtablesetintherouter.Unlessthenetworkadministratorintervenes,staticroutingwillnotchange.Sincestaticroutingcannotreflectnetworkchanges,itisgenerallyusedinnetworkswithasmallnetworkscaleandafixedtopology.Theadvantagesofstaticroutingaresimple,efficient,andreliable.Amongalltheroutes,staticrouteshavethehighestpriority.Whendynamicroutingconflictswithstaticrouting,thestaticroutingshallprevail.

Characteristicsofdynamicrouting

Dynamicroutingmeansthatroutersinthenetworkcommunicatewitheachothertotransferroutinginformationaccordingtoreal-timenetworktopologychanges,andusethereceivedroutinginformationtocalculatethroughroutingprotocols,Theprocessofupdatingtheroutingtable.

Dynamicroutingreducesmanagementtasks

Configuration

Static

Gointotheglobalconfigurationmode,definethetargetnetworknumber,thetargetnetworkNetmaskandnexthopaddressorinterface

Router(config)#iproute{nexthop-address|exit-interface}[distance]

Router(config)#iproutenetwork[mask]{address|interface}[distance][permantet]

Thetargetnetworkmaskreachesthenextrouteraddressorlocalinterfaceofthetargetnetwork

ThedefaultrouteisastaticrouteOneisthechoicethattheroutercanmakewhenthereisnomatchingentryintheroutingtablewiththedestinationaddressofthepacket

Router(config)#iproute0.0.0.00.0.0.0NextrouterInterfaceaddress

Router(config)#ipclassless

where0.0.0.00.0.0.0meansthatpacketssenttoanynetworkwillbeforwardedtothenextrouterinterfaceaddress

Ipclasslessmeansthatwhentherouterreceivesapacketthatcannotbeforwarded,itwillmatchittothedefaultroute

andreturnanICMPmessagewithanunreachabledestinationaddress

dynamic

h3>

Commondynamicroutingisdividedintodistancevectorroutingprotocol(DistanceVectorRoutingProtocol)andlinkstateroutingprotocol(Link-StateRoutingProtocol).

Dynamicroutingisaprocessinwhichroutersinthenetworkcommunicatewitheachother,transferroutinginformation,andupdatetheroutertablewiththereceivedroutinginformation.Itcanadapttochangesinthenetworkstructureinrealtime.Iftheroutingupdateinformationindicatesthatanetworkchangehasoccurred,theroutingsoftwarewillrecalculatetherouteandsendoutnewroutingupdateinformation.Thisinformationpassesthrougheachnetwork,causingeachroutertorestartitsroutingalgorithmandupdateitsownroutingtabletodynamicallyreflectnetworktopologychanges.Dynamicroutingissuitablefornetworkswithlargenetworkscaleandcomplexnetworktopology.Ofcourse,variousdynamicroutingprotocolswilloccupynetworkbandwidthandCPUresourcestovaryingdegrees.

DistancevectorroutingprotocolincludesRIP,EIGRP,IGRP

LinkstateroutingprotocolincludesOSPF,ISIS

RIP

RIPisacommonlyusedroutingprotocolintheInternet.Routerschooseroutesbasedondistance.Theroutercollectsallthedifferentpathstothedestination,andsavesthepathinformationabouttheminimumnumberofstationstoeachdestination,exceptforthedestination.Anyotherinformationotherthanthebestpathtothegroundisdiscarded.Atthesametime,therouteralsousestheRIPprotocoltonotifyotherneighboringroutersofthecollectedroutinginformation.Inthisway,thecorrectroutinginformationgraduallyspreadtotheentirenetwork.

RIPhastwodifferentversions,RIPv1andRIPv2.RIPv1.

RIPv1andRIPv2.ThemaindifferencebetweenRIPv1:

1.RIPv1isaclassfulroutingprotocol,andRIPv2isaclasslessroutingprotocol

2.RIPv1cannotsupportVLSM,RIPv2cansupportVLSM

3.RIPv1hasnoauthenticationfunction,RIPv2cansupportauthentication,andtherearetwotypesofauthentication,plaintextandMD5.

4.RIPv1doesnothavethefunctionofmanualsummarization.RIPv2canperformmanualsummarizationonthepremiseofturningoffautomaticsummarization.

5.RIPv1isbroadcastupdate,RIPv2ismulticastupdate,

6.RIPv1doesnothavethefunctionoftaggingtherouting,RIPv2cantagtheroutingforfilteringandstrategy

7.UpdatasentbyRIPv1cancarryupto25routeentries,andRIPv2canonlycarryupto24routeswithauthentication

8.Thereisnonext-hopattributeintheupdatapacketsentbyRIPv1.RIPv2hasthenext-hopattribute,whichcanbeusedtoresettherouteupdate.

RIPv1configuration;

Router(config)#routerrip

Router(config-router)#networkxxxx.xxxx.xxxx.xxxx

RIPv2configuration

Router(config)#routerrip

Router(config-router)#version2

Router(config-router)#noauto-summary

RIPiswidelyused,itissimple,reliableandeasytoconfigure.ButRIPisonlysuitableforsmallhomogeneousnetworks,becausethemaximumnumberofsitesitallowsis15,andanydestinationwithmorethan15sitesismarkedasunreachable.Moreover,theroutinginformationbroadcastofRIPevery30sisalsooneoftheimportantreasonsforthebroadcaststormofthenetwork.

EIGRP

EIGRPisproprietarytoCisco.ItisanadvanceddistancevectorroutingprotocolandusestheDUALalgorithm.EIGRPisthefastestroutingprotocoltoestablishneighborrelationships

The5Metricvalues​​ofEIGRP:Bandwidth,Load,Delay,Reliability,MTU

Configuration:

Router(config)#routereigrpXX

Router(config-router)#noauto-summary

OSPF

OSPFisaroutingprotocolbasedonlinkstate,whichrequireseachroutertosendlinkstatebroadcastinformationtoallotherroutersinthesamemanagementdomain.InthelinkstatebroadcastofOSPF,allinterfaceinformation,allmetricsandsomeothervariablesareincluded.ArouterusingOSPFmustfirstcollectrelevantlinkstateinformation,andcalculatetheshortestpathtoeachnodeaccordingtoacertainalgorithm.Thedistancevector-basedroutingprotocolonlysendsrelevantroutingupdateinformationtoitsneighboringrouters.

Configuration:

Router(config)#routerospfXX

Router(config-router)#router-idX.XXX

Router(config-router)#networkXXXX.XXXX.XXXX.XXXXareaX

OSPFdividesanautonomousdomainintoregions.Accordingly,therearetwotypesofroutingmethods:whenthesourceanddestinationareinWhenthesamearea,useintra-arearouting;whenthesourceanddestinationareindifferentareas,useinter-arearouting.Thisgreatlyreducesnetworkoverheadandincreasesnetworkstability.Whenarouterinoneareafails,itdoesnotaffectthenormaloperationofroutersinotherareasintheautonomousdomain,whichalsobringsconveniencetonetworkmanagementandmaintenance.

Staticroutinganddynamicroutinghavetheirowncharacteristicsandscopeofapplication,sodynamicroutingisusuallyusedasasupplementtostaticroutinginthenetwork.Whenapacketisroutedintherouter,therouterfirstsearchesforastaticroute,andifitfindsit,itforwardsthepacketaccordingtothecorrespondingstaticroute;otherwise,itsearchesforadynamicroute.

Workingprinciple

Router(3photos)

Whenacertaininterfaceoftherouterreceivesadatapacket,itwillcheckthedestinationnetworkaddressinthepackettodeterminewhetherthedestinationaddressofthepacketexistsinthecurrentroutingtable(thatis,doestherouterknowthepathtothedestinationnetwork).Ifthedestinationaddressofthepacketisfoundtobethesameasthenetworkaddressconnectedtoaninterfaceoftherouter,thedatawillbeforwardedtothecorrespondinginterfaceimmediately;ifthedestinationaddressofthepacketisfoundtobenotinitsdirectlyconnectednetworksegment,therouterwillcheckitsroutingtable.Findtheinterfacecorrespondingtothedestinationnetworkofthepacket,andforwarditfromthecorrespondinginterface;ifthenetworkaddressrecordedintheroutingtabledoesnotmatchthedestinationaddressofthepacket,itwillbeforwardedtothedefaultinterfaceaccordingtotherouterconfiguration,ifthedefaultinterfaceisnotconfiguredThefollowingwillreturntheICMPmessagethatthedestinationaddressisunreachabletotheuser.

Containsfunctions

Therouterincludesroutingandswitchingfunctions

Routingselectionfunction:Inordertotransmitpackets,therouterwillusethenetworkpartoftheaddressforroutingselectionTodetermineanoptimalpath

Routeswitchingfunction:enablerouterstoreceivepacketsandforwardthem

Workingprocess

Routediscovery:theprocessoflearningrouting,Dynamicroutingisusuallydonebytherouteritself,andstaticroutingneedstobemanuallyconfigured

Routingforwarding:Afterroutinglearning,datawillbeforwardedaccordingtothelearnedandupdatedroutingtable.

Routingmaintenance:TherouterregularlycommunicateswithOtherroutersinthenetworkcommunicatetounderstandnetworktopologychangesinordertoupdatetheroutingtable

TherouterrecordsthenetworkIDdirectlyconnectedtotheinterface,whichiscalleddirectroute.Theroutercanautomaticallylearndirectroutewithoutconfiguration.

Theprotocolofthelogicaladdressrecognizedbytheroutermustbesupportedbytherouter

Features

WorkingPrinciple

Therouterisathird-layernetworkEquipment,soeveryonemaynotunderstand,let'stalkabouthubsandswitchesfirst.Thehubworksatthefirstlayer(thephysicallayer).Ithasnointelligentprocessingcapabilities.Forit,dataisonlycurrent.Whenthecurrentfromoneportistransmittedtothehub,itsimplytransmitsthecurrenttootherports.Astowhetherthecomputerconnectedtootherportsreceivesthedata,itdoesnotmatter.Theswitchworksatthesecondlayer(thedatalinklayer).Itissmarterthanthehub.Forit,thedataonthenetworkisacollectionofMACaddresses.ItcandistinguishthesourceanddestinationMACaddressesintheframe.,Soyoucanestablishaconnectionbetweenanytwoports,buttheswitchdoesnotknowtheIPaddress,itonlyknowstheMACaddress.Therouterworksatthethirdlayer(thenetworklayer).Itis"smarter"thantheswitch.ItcanunderstandtheIPaddressinthedata.Ifitreceivesadatapacket,itcheckstheIPaddressinit.IfthedestinationaddressisThelocalnetworkignoresit,andifitisfromanothernetwork,thedatapacketisforwardedoutofthelocalnetwork.

Function

OurcommonhubsandswitchesaregenerallyusedtoconnecttoEthernet,butifyouconnecttwodifferentnetworktypes,suchasEthernetandATMnetwork,Hubsandswitchesareuseless.

Theroutercanconnectdifferenttypesoflocalareanetworksandwideareanetworks,suchasEthernet,ATMnetwork,FDDInetwork,tokenringnetwork,etc.Differenttypesofnetworkshavedifferentformatsandsizesofthedataunitstheytransmit-Packets.Justasroadtransportationloadsgoodsinunitsofcars,whilerailwaytransportationloadsgoodsinunitsofwagons,changingfromcartransportationtorailtransportationrequiresthegoodstobetransferredfromcarstotrainwagons,asisthedatainthenetwork..Whendataistransmittedfromonetypeofnetworktoanothertypeofnetwork,frameformatconversionmustbeperformed.Routershavethiscapability,butswitchesandhubsdonot.

Infact,whatwecallthe"Internet"meansthatvariousroutersconnectvariousnetworktypestoeachother.Hubsandswitchesaresimplynotuptothistask,soroutersmusttakeonthisrole.

Withpathselectioncapability

IntheInternet,theremaybemanypathsfromonenodetoanother.Theroutercanchoosetheunobstructedshortestpath,whichgreatlyincreasesthecommunicationspeed,reducesthecommunicationloadofthenetworksystem,andsavesnetworksystemresources.Thisisalsoaperformancethathubsandswitchessimplydonothave.

Routingprotocolandbypassableprotocol

Sometimesroutingprotocolandbypassableprotocolareoftenconfusing:

• Bypassableprotocol:Anynetworkprotocolthatprovidesenoughnetworklayeraddressinformationsothatpacketscanbeforwardedfromonedevicetoanotherwithoutknowingtheentirepathfromsourcetodestination.The"passableprotocol"definesthepacketformatandhowthepacketfieldsareused.Packetsareusuallydeliveredfromoneendsystemtoanother.IPisaprotocolthatcanberouted,andEthernetisanexampleofaprotocolthatcannotberouted.

• Routingprotocol:Exchangeroutinginformationbetweennetworkssothattheroutercandynamicallyestablishaprotocolforroutingtables.TraditionalIProutingisverysimple,becauseitusesthenextnoderoutingmethod,thatis,therouteronlyneedstoconsiderwhich"nextnode"thepacketissentto,withoutconsideringtheentiredestination.Paths.

Althoughdynamicroutingmaybeverycomplicated,itmakestheInternetveryflexible,andthescaleoftheInternethasgrownbymorethaneightordersofmagnitudesincetheadoptionofIP.

Routingmetriccontainsallthevalues​​usedbyroutingalgorithmstodeterminewhichpathisbetterthananother.Themetricmayincludealotofinformation,suchasbandwidth,delay,numberofpassingnodes,pathcost,load,MTU,reliability,andtransmissioncost.Theroutingtableonlystoresthebestpossiblepath,buttheconnectionstatusortopologydatabasemaystoreotherrelatedinformation.

Whenroutersfindmultipledifferentpathstothesamedestinationfromdifferentroutingprotocols,theyuseafeaturecalledadministrativedistancetoselectThebestpath.Theadministrativedistancedefinesthereliabilityoftheroutingagreement.Eachroutingprotocolisprioritizedaccordingtothemanagementdistancevalue,fromthemostreliabletotheleastreliable.

Accordingtotherelationshipbetweenroutersandotherautonomoussystems,therearemanytypesofroutingprotocols:

• AdhocnetworkroutingprotocolsappearinNooralittlebasicnetwork.SeethelistofAdhocroutingagreementsfortheproposedagreement.

• InternalGatewayProtocol(IGPs)exchangeroutinginformationinasingleautonomoussystem.Commonexamplesinclude:

• IGRP(InteriorGatewayRoutingProtocol)

• EIGRP(EnhancedInteriorGatewayRoutingProtocol))

• OSPF(OpenShortestPathFirst)

• RIP(RoutingInformationProtocol)

• IS-IS(IntermediateSystemtoIntermediateSystem)

• ExternalGatewayProtocol(EGPs)Exchangeroutinginformationindifferentautonomoussystems.EGPincludes:

• EGP(theexternalgatewayprotocolusedtoconnecttotheInternetbackboneisnolongerused)

• BGP(BorderGatewayProtocol:theversionusedaround1995,BGPv4)

Type

Access

AccessrouterreferstotherouterequipmentthatconnectsLANuserstotheWAN.ThemostcontactedbyourLANusersistheaccessrouter.WhereverthereisInternet,therewillbearouter.IfyouaccesstheInternetviaasharedLANline,youwilldefinitelyusearouter.

Somereadersmayhavequestions:IuseaproxyservertoaccesstheInternet.CanIaccesstheInternetwithoutarouter?Infact,aproxyserverisalsoakindofrouter,acomputerplusanetworkcard,plusISDN(orModemorADSL),andtheninstalltheproxyserversoftware,infact,ithasconstitutedarouter,buttheproxyserverusessoftwaretoimplementroutingFunction,andtherouteruseshardwaretorealizetheroutingfunction,justliketherelationshipbetweentheVCDsoftdecompressionsoftwareandtheVCDmachine,thestructureisdifferent,butthefunctionisthesame.

Enterprise-class

Enterprise-classroutersareusedtoconnectthousandsofcomputersinlargeenterprises,whicharenotaccessibletoordinaryLANusers.Comparedwithaccessrouters,enterprise-levelrouterssupportmultiplenetworkprotocolsandfastspeeds.TheyhavetodealwithvariousLANtypes,supportmultipleprotocols,includingIP,IPX,andVine,aswellassupportfirewalls,packetfiltering,andalargenumberofmanagementandSecuritypolicyandVLAN(virtuallocalareanetwork).

Backbone-level

Onlytechniciansworkinginafewdepartmentssuchastelecommunicationscanaccessbackbone-levelrouters.TheInternetiscomposedofdozensofbackbonenetworks,eachofwhichservesthousandsofsmallnetworks,andbackboneroutersrealizetheinterconnectionofenterprise-levelnetworks.Therequirementsforitarespeedandreliability,whilepriceisofsecondaryimportance.Hardwarereliabilitycanbeobtainedbyusingtechnologiesusedintelephoneswitchingnetworks,suchashotbackup,dualpowersupplies,anddualdatachannels.Thesetechnologiesarenecessaryforallbackbonerouters.

Therouterterminalsystemonthebackbonenetworkisusuallynotdirectlyaccessible.TheyareconnectedtotheISPandcorporatenetworkonthelong-distancebackbonenetwork.TherapiddevelopmentoftheInternethasbroughtconsiderablechallengestobackbonenetworks,enterprisenetworks,andaccessnetworks.

Protocolsholdinglogicaladdressesthatneedtobeidentified

Contrast

Softroutingreferstotheuseofdesktopsorserverswithsoftwaretoformaroutingsolution,mainlyrelyingonsoftwareThesettingoftheroutercanachievethefunctionoftherouter;andthehardrouterisaspecialhardwaredevice,includingtheprocessor,powersupply,andembeddedsoftware,toprovidetherouterfunctionofthesetting.

Undernormalcircumstances,softroutingisusuallyacomputer.Hardwareroutingcanbeclassifiedaccordingtodifferentstandards.Forexample,itcanbedividedintohigh,medium,andlow-endintermsofperformance,andfixedintermsofstructure.Configurationandmodularityandsoon.

Therearemanybenefitsofsoftrouting.Forexample,usingcheapdesktopcomputers,withfreeLinuxsoftware,softroutingismoreflexible,anddesktopprocessorsarepowerful,sotheprocessingefficiencyisgood,anditiseasiertoexpand..However,correspondingly,techniciansarealsorequiredtohavemoreprofessionalknowledgesuchassettingmethods,parameterdesign,etc.Atthesametime,thesettingismorecomplicated,andthetechniciansarerequiredtohaveacertaintechnicalabilitytorespond.Atthesametime,ifthehardwareconfigurationofthedesktopcomputerisnotwellorunreasonablyselected,andifthefunctionoftherouterworksforalongtime,theprobabilityoffailurewillbehigh.Thecostofbuildingwithadesktopcomputerisnotlow,butifyouwanttouseaserver,thecostisevenhigher,andthelearningprocessfortechniciansismorecumbersome.

Themethodofhardroutingistoconfigureadedicatedmachine.LikeaPC,ahardrouterincludespowersupply,internalbus,mainmemory,flashmemory,processor,andoperatingsystem.Itisdesignedforroutingfunctionsandhasarelativelyhighcost.Low.Thesoftwareintherouterisdeeplyembeddedinthehardware,includingtheoptimizationofvariousdevicedrivers,differentoptimizationstrategiesfordifferentsystemCPUs,etc.Thissoftwareisnotapplicationsoftware,butsystemsoftware,andcannotbeseparatedfromhardware.

Becausethearchitecturedesignconsidersthelong-termoperation,thestabilityhasahigherguarantee.Inaddition,mostoftheimportantfunctionshavebeencompletedinthebuilt-insystemdesign,sothemanualmanagementsettingsareverylaborious.Less,cansavethetimeoftechnicalornetworkmanagementpersonnel.Butontheotherhand,ifacertainhardwarespecificationisnotstrongandexpandabilityisnotwide,itmaynotbeabletomeetthedemand,especiallywhenadditionalfunctionsneedtobeadded,ifthemanufacturerdoesnotprovideit,thenthetechnicalornetworkmanagementpersonnelwillnotbeabletosolveit..

Theaboveanalysisismoresubjective,butitalsobasicallysummarizestheoverallcharacteristicsreasonably.ThefollowingisamorecomprehensiveandaccurateanalysisofthecomparisonofsoftandhardroutingforReadersandfriendsforreference.

Concept

Softroutersareusuallyservedbyordinarycomputers,usinggeneraloperatingsystems,suchaslinuxorwindows,sotheroutingsettingsareinfactwindowsorlinuxsettings,orforcomputersConfiguration.ThePCcanbeaveryold486oramoreadvancedPC/server.Softwareandhardwareareindependent;hardwarerouters,mostlybasedonembeddedsystemarchitecture,useself-developedorready-madeembeddedoperatingsystemssuchasVxworks,Montavista,uClinux,etc.asoperatingsystems,andthencooperatewithsystemmanufacturerstodeveloptheirownRoutingsoftware,softwareandhardwarearecoordinatedwitheachother.Thehardwarerouteradoptsaspecialoperatingsystem,sothehyperterminal(computer)isusedtorealizethemanagementoftherouterthroughtheconsole.Themanagementofhardwareroutersisusuallyimplementedbydedicatedcommandlines,graphicalinterfaces,ornetworkmanagementsoftware.

Hardwarearchitecture

Thehardwarearchitectureofthesoftwarerouterisuniversal,suitablefortheinstallationanduseofvariousapplicationsoftware,notonlydesignedforrouters;whilethehardwarearchitectureofthehardwarerouterisspecializedDesignedforrouters,someCPUsaredevelopedfornetworkapplications.

Hardwareassembly

Usersofsoftwareroutersmayhavetoassemblehardwarebythemselves.NormalPCsmaynothaveanetworkcard(suchastheveryold486)oronlyhaveonenetworkcard.Youmustinstalladditionalnetworkcardstomeettheroutingfunction.Thehardwaremayhavecompatibilityissues,andusersmustsolvethembythemselves;andhardwarerouterusersdonotneedtoassemblethehardwarebythemselves.Thehardwarematchingdesignhasbeencompletedbythesystemmanufacturerandhasundergonerigoroustesting.Therewillbenoincompatibility.

Softwareinstallation

Softwarerouterusersmustinstallthesoftwarebythemselves.Somesoftwareisfree,andsomearesubjecttoroyalties;whilehardwarerouterusersdonotneedtoinstallsoftwarebythemselves.Itiscontainedintheflashmemoryoftheproduct.

SoftwareMaintenance

Thefreesoftwareprovidedbythesoftwarerouterisusuallyanon-commercialopenprogramcode,whichisusuallydevelopedandmodifiedbyexpertsscatteredaroundbecauseofinterest.Thecompletenessanddebuggingofthefunctionscannotbeguaranteed;thesoftwarefunctionsofthehardwareroutersaredevelopedbythesystemmanufacturersthatlaunchedtheproducts,andtheconsistencyishigh.Theadditionoffunctionsanddebuggingaremaintainedbythesystemmanufacturer.Usersonlyneedtoupgradethesoftware.Thereisareliablechannelforobtainingtheupgradedsoftware,andtheafter-salesserviceisguaranteed.

Compatibility

Thesoftwareroutersoftwaremustadapttotheready-madehardware(suchasPC)andtheready-madeoperatingsystem(suchasWindowsandLinux).Thehardwareandoperatingsystemarenotdesignedforthenetwork./Routingfunctionisdesigned.Stabilitycannotbegeneralized.Usersmustpayrelativecosts,time,energy,andmoney.Thesoftwareandhardwareofhardwareroutersuseembeddedoperatingsystemsandmatcheachother,sotheoveralldesignisstreamlinedandefficient.Itisnotonlystable,butalsoTheinstallationiseasy,andtheproductcostplusthecostpaidbytheuserisrelativelylow.

Usingtheinterface

Inthesoftwarerouter,differentsoftwarehasdifferentmethods,somearewindowscreens,andsomearecommandlineinstructions.Notnecessarilyeasytounderstand.Somerequireveryprofessionalknowledge;andhardwareroutersaremostlysetintheformofWebGUI,emphasizinguserfriendly,andmakingsimpleandeasy-to-understandsettingmethodsbasedonspecificfunctions.

Intermsofleveldifference

Thereisnodifferenceinsoftwarerouters,andtheperformancedependsonthePCandsoftwareselectedbythetester.Soitmaynotbeapplicabletovariousnetwork/routingapplications.Themoreadvancedtheapplicationenvironmentrequiresthemoreprofessionalknowledgetocopewithit;hardwarerouterswilldevelopdifferentlevelsofroutersfordifferentlevelsofnetwork/routingapplicationstoachievebettercostperformance.

Intermsofworkingenvironment

ThesoftwareroutercanonlyworkontheEthernetnetworktorealizetheinterconnectionbetweenthelocalareanetworks.Hardwareroutershaveawealthofinterfacetypes,sotheyaresuitableforvarioustypesofnetworks,andcanbeusedfortheinterconnectionoflocalareanetworksaswellastheinterconnectionofwideareanetworksandtheInternet.Inaddition,theefficiencyofthetwoisalsodifferent.Softroutingcanbeappliedtosmall-scale\lowcommunicationefficiencynetworks,andhardwareroutingcanbeappliedtolarge,mediumandsmallnetworkswithhighcommunicationefficiency.

Application

Ingeneral,differentproductsaresuitablefordifferentcustomergroups.Fromtheperspectiveofmanyproductdevelopments,thesoftwareapproachissuitableformoretechnicallycapablenetworkmanagement,whilethegeneralnetworkmanagementhopestofocusonothermorevaluableplaces,moreuseofhardrouting.Duetothelimitationofthecomputer,thesoftroutercanonlyusetheEthernetcard,soitisbasicallylimitedtotheconnectionbetweentheEthernetnetworks.TheconnectionofthesoftrouterwillbeusedonlywhenmultiplenetworksegmentsaredividedbetweentheEthernetnetworks.

Ifthenetworkislargeenoughtobedividedintosubnets,thentheefficiencyofsoftroutingisobviouslynotenoughforhigh-speedcommunicationbetweennetworks.Intermsofprice,softroutingisthepriceofacomputer,whilethepriceofhardwareroutingvariesgreatlydependingontheperformance.Tobehonest,ifonlyNATisimplemented,theefficiencyofthecomputerishigherthanthatofthehardwarerouter.

Combinedwithvariousconsiderations,buyersmustfullyunderstandtheirownnetworkenvironmentandinvestmentplanstoconsiderhowtochoosearouter.TheauthorwillgiveanexampletoanalyzetheworkingenvironmentrequirementsofInternetcafes.Internetcafeshavethefollowingrequirementsforroutersincommon:strongenoughdataprocessingcapabilities,high-speedanduninterruptedInternetaccess,nodisconnectionorpauseunderbigdatatraffic;highstabilityandreliability,andlong-termuninterruptedstabilityWork;itmusthavestrongcompatibilityandbeabletoadapttodifferentaccessservicesofdifferentoperators;easytoinstall,easytoconfigure,easytomanage,easytouse,user-friendlyandeasytounderstand;underthepremiseofensuringperformance,theremustbeaReasonableprice,withexcellentperformance-priceratio.

SoforanInternetcafewithacertainscale,theyaremoreinclinedtousehardrouting,andtheuseofhardwareroutersbringsgreateradvantages,suchasmoldingequipment,nomaintenanceforonedebugging,nomaintenanceofpartsTrouble;professionalmanufacturertechnicalsupport,freeprofessionalsoftwareupgrades;canachievelinebackup,loadbalancing,strategicroutingandmanyotherapplicationsthatareinlinewithInternetcafes;mostproductsusenetworkdedicatedCPUstosolvecomplexnetworkroutingproblems;professionaltechnicaltrackingcansolvethecontinuousNewproblemsinemergingnetworkapplicationswillbesolvedforfreeandsoon.