Chapter9IPv6TunnelConguration
inanothersubnetoranotherusernetwork.Anotherconditionis
theprexofthenextdestinationaddresscontainsthespecial6to4
TLAvalue2002::/16.
IPv4sourceaddressiscontainedinthe6to4prexoftherequest-
ingsite,thatis,theIPv4addressofthenetworkexternalinterface
ofthe6to4routeriscontainedinthe6to4prexoftheIPv6packet.
Atthesametime,theIPv4addressofthereceivingsitebecomes
the6to4prexofdestinationaddressofthenextIPv6sending
packet.
Whenthe6to4routerofthereceivingsitereceivesanIPv4packet
anddeterminesthatitistheType41IPv4protocol,itwillimple-
menttheIPv4securityinspection,removetheheaderandconduct
localtransmissionwiththeIPv6sourcepacket.
Thetransmissionrulementionedaboveistheuniquerevisionto
IPv6transmissionrule,becausethereceivingruleoftheprimary
IPv6translationmechanismhasbeendeterminedalready.By
addingpropernumberof6to4prexesintoDNS,allsitescan
cooperatewitheachotherwithoutmanualtunnelconguration.
IPv6/IPv4DualStackTechnology
DuringtheIPv6upgradingprocess,therearesomeapplications
havebeenupgradedbutotherapplicationshavenotbeenup-
gradedonnetworknode.TheupgradedapplicationsuseIPv6pro-
tocolstack,andun-upgradedapplicationsuseIPv4protocolstack.
Tomakethemcoexist,IPv6/IPv4dualstacktechnologyisused.
TheupgradedapplicationscaneitheradoptIPv4IPv4protocol
stack,andcanadoptIPv6protocolstack.
Table10showstheprotocolstructureoftheIPv6/IPv4dualstack.
TABLE10PROTOCOLSTRUCTUREOFTHEIPV6ANDIPV4DUALSTACK
Applicationlayerprotocol
TCP/UDPprotocol
IPv6protocolIPv4protocol
Linklayerandphysicalprotocol
NetworkAddressTranslation
Technology
NetworkAddressTranslation(NAT)technologyregardsIPv4ad-
dressesandIPv6addressesasinternaladdressesandglobalad-
dressesrespectively,andviceversa.
WhenaninternalIPv4hostcommunicateswithanexternalIPv6
host,itwilltranslatetheIPv4address(equivalenttotheinternal
address)totheIPv6address(equivalenttotheglobaladdress)
CondentialandProprietaryInformationofZTECORPORATION67