3Com S7902E, Руководство по настройке

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As shown in Figure 1-9 , Host B and Host C are multicast information receivers. They send IGMPv3
report messages to the respective DRs to express their interest in the information of the specific
multicast source S.
Upon receiving a report message, the DR first checks whether the group address in this message falls
in the SSM group range:
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If so, the DR sends a subscribe message for channel subscription hop by hop toward the 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 PIM-SSM.
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If not, the PIM-SM process is followed: the DR needs to send a (*, G) join message to the RP, and
a multicast source registration process is needed.
In PIM-SSM, the “channel” concept is used to refer to a multicast group, and the “channel subscription”
concept is used to refer to a join message.
Multi-Instance PIM
A multicast router running multiple instances maintains an independent set of PIM neighbor table,
multicast routing table, BSR information and RP-set information for each instance.
Upon receiving a multicast data packet, the multicast router determines the VPN instance the data
packet belongs to, and then forwards the packet as per the multicast routing table of that VPN instance
or creates a multicast routing table entry for that VPN instance.
Protocols and Standards
PIM-related specifications are as follows:
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RFC 4601: Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification
(Revised)
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RFC 3973: Protocol Independent Multicast-Dense Mode (PIM-DM): Protocol
Specification(Revised)
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RFC 4607: Source-Specific Multicast for IP
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RFC 5059: Bootstrap Router (BSR) Mechanism for Protocol Independent Multicast (PIM)
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Draft-ietf-ssm-overview-05: An Overview of Source-Specific Multicast (SSM)
Configuring PIM-DM
PIM-DM Configuration Task List
Complete these tasks to configure PIM-DM:
Task Remarks
Enabling PIM-DM
Required
Enabling State-Refresh Capability Optional