H3C Technologies H3C S12500 Series Switches - Manual (Page 397)

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• SPT building
Neighbor discovery
IPv6 PIM-SSM uses the same neighbor discovery mechanism as in IPv6 PIM-SM. For more information,
see "
Neighbor discovery ."
DR election
IPv6 PIM-SSM uses the same DR election mechanism as in IPv6 PIM-SM. For more information, see " DR
election ."
SPT building
Whether to build an RPT for IPv6 PIM-SM or an SPT for IPv6 PIM-SSM depends on whether the IPv6
multicast group that the receiver will join is in the IPv6 SSM group range. The IPv6 SSM group range that
IANA has reserved is FF3x::/32, where x represents any legal address scope.
Figure 108 Building an SPT in IPv6 PIM-SSM
As shown in Figure 108 , Hosts B and C are IPv6 multicast information receivers. They send an MLDv2
report message to the respective DRs to announce that they are interested in information about a specific
IPv6 multicast source S and that sent to the IPv6 multicast group G.
The DR that has received the report first determines whether the IPv6 group address in this message is in
the IPv6 SSM group range:
• If so, the IPv6 PIM-SSM model is built. The DR sends a channel subscription message hop by hop
toward the IPv6 multicast source S. An (S, G) entry is created on all routers on the path from the DR
to the source. Thus, an SPT is built in the network, with the source S as its root and receivers as its
leaves. This SPT is the transmission channel in IPv6 PIM-SSM.
• If not, the IPv6 PIM-SM process is followed. The receiver-side DR sends a (*, G) join message to the
RP, and the IPv6 source-side DR starts an IPv6 multicast source registration process.
Protocols and standards
• RFC 3973, Protocol Independent Multicast-Dense Mode(PIM-DM):Protocol Specification(Revised)
• RFC 4601, Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification (Revised)
Source
Server
Host A
Host B
Host C
Receiver
Receiver
IPv6 multicast packets
SPT
Subscribe message
DR
DR
RP