Zte ZXR10 5900E Series - Figure 4-3 Three Times of Handshaking

ZXR105900ESeriesCongurationGuide(IPv4Routing)
shortedtoN-SEL)issimilartotheprotocolIDinanIPaddress.Differenttransmission
protocolshavedifferentSELs.InanIPaddress,theSELis00.
IS-ISneighborestablishment
TheIS-ISdistinguishesnetworksaspoint-to-pointnetworksandbroadcastnetworks.The
neighborestablishprocessesaredifferentonthesetwotypesofnetworks.
lEstablishneighboronapoint-to-pointlink
IftheIntermediateSystem(IS)onthenetworkisconguredwiththeIS-ISrouting
protocolandtheinterfaceisinUPstate,thesystemsendsIIHPDUpackets.Theother
neighboringintermediatesystemsperformthefollowingoperationsafterreceivingthe
packets:
WhentheISreceivesapoint-to-pointIIHPDUpacket,itcomparestheareaaddresses
ofthesetwoISstoensurethattheneighborcanbeestablished.IfthetwoISshave
thesameareaaddress,theneighborcanbeestablishedforallISroutercombinations
(excepttheconnectionbetweenoneL1ISandoneL2OnlyIS).However,ifthearea
addressesaredifferent,theneighborcanonlybeestablishedbetweentwoL2ISs.
Onapoint-to-pointnetwork,iftheareaaddressiscorrect,thelocalintermediate
systemmatchesthecircuittypeofthereceivedIIHPDUpacketwiththatinthelocal
intermediatesystem.Iftheymatcheachother,neighborrelationcanbeestablished,
theneighborinformationisaddedtotheneighbordatabase,andtheneighborstateis
settoUP .Ifthecircuittypesdonotmatcheachother,thispacketisdropped.
TheaboveneighborestablishmentprocessisproposedinRFC1142,whichisbased
onthepremisethatthepoint-to-pointnetworkisabsolutelyreliable.However,the
networkisnotnecessarilyreliably.Therefore,theRFC3373introducedtheTLV.
Establishneighborrelationafterthreetimesofhandshaking,seeFigure4-3.
Figure4-3ThreeTimesofHandshaking
TheIIHPDUsentbyrouterRTAcarriesthetype240TLV,inwhich,theneighbor's
threestatesaresaved.WhenrouterRTBreceivesthepacket,itconrmsthenext
neighborstateaccordingtothestateofitsneighborandtheneighborstateintheTLV.
Forthestatechanges,refertoT able4-1.
Table4-1NeighborStateChanges
-DownInitUp
DownInitUpDown
4-4
SJ-20150114102049-003|2015-01-15(R1.0)ZTEProprietaryandCondential