Ssm Model Implementation In Ipv6 Pim - 3Com MSR 50 Series Configuration Manual

1244 C 74: IP 6 PIM C
HAPTER V
SSM Model
Implementation in IPv6
PIM
ONFIGURATION
After the RPT-to-SPT switchover, IPv6 multicast data can be directly sent from the
source to the receivers. IPv6 PIM-SM builds SPTs through RPT-to-SPT switchover
more economically than IPv6 PIM-DM does through the "flood and prune"
mechanism.
Assert
IPv6 PIM-SM uses exactly the same assert mechanism as IPv6 PIM-DM does. Refer
to "Assert" on page
The source-specific multicast (SSM) model and the any-source multicast (ASM)
model are two opposite models. Presently, the ASM model includes the IPv6
PIM-DM and IPv6 PIM-SM modes. The SSM model can be implemented by
leveraging part of the IPv6 PIM-SM technique.
The SSM model provides a solution for source-specific multicast. It maintains the
relationships between hosts and routers through MLDv2. IPv6 PIM-DM
implements IPv6 multicast forwarding by building SPTs rooted at the IPv6 multicast
source through the "flood and prune" mechanism. Although an SPT has the
shortest path, it is built in a low efficiency. Therefore the IPv6 PIM-DM mod is not
suitable for large- and medium-sized networks.
In actual application, part of the IPv6 PIM-SM technique is adopted to implement
the SSM model. In the SSM model, receivers know exactly where an IPv6 multicast
source is located by means of advertisements, consultancy, and so on. Therefore,
no RP is needed, no RPT is required, and is no source registration process is needed
for the purpose of discovering IPv6 multicast sources in other IPv6 PIM domains.
Compared with the ASM model, the SSM model only needs the support of MLDv2
and some subsets of IPv6 PIM-SM. The operation mechanism of the SSM model in
an IPv6 PIM domain can be summarized as follows:
Neighbor discovery
■
DR election
■
SPT building
■
Neighbor discovery
IPv6 PIM-SSM uses the same neighbor discovery mechanism as in IPv6 PIM-SM.
Refer to "Neighbor discovery" on page
DR election
IPv6 PIM-SSM uses the same DR election mechanism as in IPv6 PIM-SM. Refer to
"DR election" on page
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 the receiver is to join falls in the IPv6 SSM group
address range (the IPv6 SSM group address range reserved by IANA is FF3x::/32,
where x represents any legal scope).
1238.
1236.
1239.