Protocols And Standards - 3Com MSR 50 Series Configuration Manual

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Protocols and Standards

Figure 364 Building an SPT in IPv6 PIM-SSM
Source
Server
SPT
Subscribe message
IPv6 multicast packets
As shown in Figure 364, Hosts B and C are IPv6 multicast information receivers.
They send an MLDv2 report message marked (include S, G) to the respective DRs
to announce that they are interested in the information of the specific IPv6
multicast source S and that sent to the IPv6 multicast group G. If they need
information from other sources than S, they send an (exclude S, G) report. No
matter what the description is, the position of IPv6 multicast source S is explicitly
specified for receivers.
The DR that has received the report first checks whether the IPv6 group address in
this message falls in the IPv6 SSM group address range:
If so, the IPv6 PIM-SSM model is built: the DR sends a channel subscription
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message hop by hop toward the IPv6 multicast source S. An (include S, G) or
(exclude 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 DR needs to send a (*, G) join
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message to the RP, and an IPv6 multicast source registration process is needed.
In IPv6 PIM-SSM, the "channel" concept is used to refer to an IPv6 multicast group,
and the "channel subscription" concept is used to refer to a join message.
IPv6 PIM-related specifications are as follows:
RFC 2362: Protocol Independent Multicast-sparse Mode(PIM-SM):Protocol
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Specification
RFC 3973: Protocol Independent Multicast-Dense Mode(PIM-DM):Protocol
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Specification(Revised)
RFC 3956: Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast
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Address
draft-ietf-pim-sm-v2-new-06: Protocol Independent Multicast-Sparse Mode
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(PIM-SM)
RP
IPv6 PIM Overview 1245
Host A
Receiver
DR
Host B
DR
Receiver
Host C