Route Discovery Protocols

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1、RouteRouteDiscoveryDiscoveryProtocolsProtocolsRajJainTheOhioStateUniversityColumbus,OH43210Jain@CIS.Ohio-State.Eduhttp://www.cis.ohio-state.edu/~jain/TheOhioStateUniversityRajJain1OverviewBuildingRoutingTablesRoutingInformationProtocolVersion1(RIPV1)RIPV2OSPFBGPandIDRPRef:M.Na

2、ugle,NetworkProtocols,McGrawHill,1998.TheOhioStateUniversityRajJain2AutonomousSystemsAutonomousSystemsAninternetconnectedbyhomogeneousroutersundertheadministrativecontrolofasingleentitySubnet1.2Subnet1.2R6InteriorR3R2Subnet1.2R5Subnet1.2Subnet1.2R7R8R4Subnet1.2R1ExteriorSubnet

3、1.2Subnet1.2TheOhioStateUniversityFig16.10RajJain3RoutingProtocolsRoutingProtocolsInteriorRouterProtocol(IRP):Usedforpassingroutinginformationamongroutersinternaltoanautonomoussystem.AlsoknownasIGP.mExamples:RIP,OSPFExteriorRouterProtocol(ERP):Usedforpassingroutinginformationa

4、mongroutersbetweenautonomoussystems.AlsoknownasEGP.mExamples:EGP,BGP,IDRPNote:EGPisaclassaswellasaninstanceinthatclass.TheOhioStateUniversityRajJain4RoutingInformationProtocolRoutingInformationProtocolRIPusesdistancevectorÞAvectorofdistancestoallnodesissenttoneighborsEachroute

5、rcomputesnewdistances:mReplaceentrieswithnewlowerhopcountsmInsertnewentriesmReplaceentriesthathavethesamenexthopbuthighercostmEachentryisaged.RemoveentriesthathaveagedoutSendoutupdatesevery30seconds.TheOhioStateUniversityRajJain5Distance-VectorExampleDistance-VectorExampleDest

6、i-NextDesti-NextnationDelaynodenationDelaynode10Ñ23110Ñ222032222353302334414220414563311524683533644D1S1D2D3D411,2=211,3=511,4=1(a)Node1ås(b)Delayvectorssent(c)Node1åsroutingtableroutingtabletonode1fromafterupdateandlinkbeforeupdateneighbornodescostsusedinupdateFig9.9Stallings

7、TheOhioStateUniversityRajJain6RIPV1RIPV1RFC1058adoptedin1988ImplementedinBerkeleyUNIXasrouted(pronouncedrouted)BothhostsandrouterscanimplementRIPHostsusepassivemodeÞDonotsendoutupdatesRunsonUDPRIPpacketsdonotleavelocalnetworkTheOhioStateUniversityRajJain7RIPv1PacketFormatRIPv1

8、PacketFormatCommandVersionReservedFamilyofNet1ReservedNet1Add