3com 5500-ei pwr Installation Instruction
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2) Receivers send join messages to the nearest RP to join in the RPT rooted as this RP. In this
example, Receiver joins the RPT rooted at RP 2.
3) RPs share the registered multicast information by means of SA messages. In this example, RP 1
creates an SA message and sends it to RP 2, with the multicast data from Source encapsulated in
the SA message. When the SA message reaches RP 2, RP 2 decapsulates the message.
4) Receivers receive the multicast data along the RPT and directly join the SPT rooted at the multicast
source. In this example, RP 2 forwards the multicast data down the RPT. When Receiver receives
the multicast data from Source, it directly joins the SPT rooted at Source.
The significance of Anycast RP is as follows:
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Optimal RP path: A multicast source registers with the nearest RP so that an SPT with the optimal
path is built; a receiver joins the nearest RP so that an RPT with the optimal path is built.
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Load balancing between RPs: Each RP just needs to maintain part of the source/group information
within the PIM-SM domain and forward part of the multicast data, thus achieving load balancing
between different RPs.
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Redundancy backup between RPs: When an RP fails, the multicast source previously registered
on it or the receivers previous joined it will register with or join another nearest RP, thus achieving
redundancy backup between RPs.
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Be sure to configure a 32-bit subnet mask (255.255.255.255) for the Anycast RP address, namely
configure the Anycast RP address into a host address.
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An MSDP peer address must be different from the Anycast RP address.
Protocols and Standards
MSDP is documented in the following specifications:
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RFC 3618: Multicast Source Discovery Protocol (MSDP)
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RFC 3446: Anycast Rendezvous Point (RP) mechanism using Protocol Independent Multicast
(PIM) and Multicast Source Discovery Protocol (MSDP)
Configuring MSDP Basic Functions
A route is required between two routers that are MSDP peers to each other. Through this route, the two
routers can transfer SA messages between PIM-SM domains. For an area containing only one MSDP
peer, known as a stub area, the route is not compulsory. SA messages are transferred in a stub area
through the configuration of static RPF peers. In addition, the use of static RPF peers can avoid RPF
check on the received SA messages, thus saving resources.
Before configuring static RPF peers, you must create an MSDP peering connection. If you configure
only one MSDP peer on a router, the MSDP peer will act as a static RPF peer. If you configure multiple
RPF peers, you need to handle them by using different rules according to the configured policies.
When configuring multiple static RPF peers for the same router, you must follow the following two
configuration methods: