Zte ZXR10 5900E Series - Figure 4-7 Diffusion and Database Synchronization on a Broadcast Link

ZXR105900ESeriesCongurationGuide(IPv4Routing)
Onbroadcastlinks,LSPisdiffusedtoadjacentroutersonlayer1andlayer2through
broadcastaddressesALLL1SandALLL2S.Thediffusiononbroadcastlinksdoes
notrequirereliabletransmission.
Unreliablediffusionrequiresamechanismtoguaranteedatabasesynchronization.
TheIS-ISrouterusestheDIStobroadcastCNSPperiodicallytoimplementdatabase
synchronizationonbroadcastlinks.
TheDIScontrolsthediffusionanddatabasesynchronizationonbroadcastlinks.The
IS-ISprotocoldoesnotrequirethattheIS-Isrouterscanonlyestablishadjacent
relationwithDISonbroadcastlinks.Afterthehellopacketisbroadcastedandthree
timesofhandshaking,adjacentrelationcanbeestablishedbetweenrouters.Three
timesofhandshakingmeansthatallroutersreportthedetectedrouters.TheCSNP
sentbytheDISistransmittedperiodicallytoensurethatallroutersontheLAN
receivesacopy.ThroughcomparingtheCNSPandthatinthelinkstatedatabase,
themissingLSPandnewversionLSPcanberecognized.Theroutercanthensend
thePSNPpackettoapplyfortheLSP .
BroadcastingCSNPperiodicallyconsumeslotsofbandwidthandthusthecostishigh.
However,thisisasimplereliabletransmissionpolicyonabroadcastlink.Youcan
reducethesendingfrequencybyincreasingthesendinginterval.
RTAandRTBareconnectedtothelink,andRTCisthelastrouterthatisconnected
tothelink.TheRTAlinkstatedatabasecontainsRTA.00-00,RTA.01-00(pseudolsp),
andRTB.00-00,seeFigure4-7.
Figure4-7DiffusionandDatabaseSynchronizationonaBroadcastLink
1.RTCgeneratesanLSP(RTC.00-00)afterRTAestablishestheadjacentrelation
withRTB.RTCthencopiestheLSPandsavesittoitsdatabase.Afterthis,RTC
diffusesanothercopytothelinkthroughinterface3.
2.RTAthatoperatesastheDISadvertisesaCSNPtothelinkinbroadcastmode.
3.AfterRTCreceivestheCSNP ,itcomparestheCSNPwiththatinthelocallink
statedatabase.ItndsthatthreeLSPsareunavailable:RTA.00-00,RTA.01-00,
andRTB.00-00.RTCsendsaPSNPtothelinktorequestfortheLSPs.
4.RTAsendsRTA.00-00,RTA.01-00,andRTB.00-00inbroadcastmode.AfterRTC
receivesthecopies,theRTC'sdatabasecanbesynchronizedwiththeRTA's
database.
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SJ-20150114102049-003|2015-01-15(R1.0)ZTEProprietaryandCondential