Introduction To Msdp - 3Com 5500-SI Configuration Manual

MSDP C
ONFIGURATION
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Among Switch 5500 Series Ethernet Switches, only Switch 5500-EI Series Ethernet
Switches support the configurations described in this chapter.
Routers and router icons in this chapter represent routers in the common sense and
Ethernet switches running routing protocols.

Introduction to MSDP

Internet service providers (ISP) are not willing rely on devices of their competitors to
forward multicast traffic. On the other hand, ISPs want to obtain information from
information sources no matter where the information resources reside and forward
the information to their own members. The multicast source discovery protocol
(MSDP) is designed to address this issue and used to discover multicast sources in
other protocol independent multicast sparse mode (PIM-SM) domains. MSDP is only
valid for the any-source multicast (ASM) model.
MSDP describes a mechanism of interconnecting multiple PIM-SM domains. It
requires that the inter-domain multicast routing protocol must be PIM-SM and allows
the rendezvous points (RPs) of different domains to share multicast source
information.
MSDP peers
The RP in a PIM-SM domain can sense the existence of an active multicast source S, if
any, in this domain through multicast source register messages. If a PIM-SM domain
managed by another ISP wants to obtain information from this multicast source, the
routers in both PIM-SM domains must establish an MSDP peering relationship with
each other, as shown in Figure 169.
Figure 169 MSDP peering relationship
user
R P 2
P IM -S M 2
user
S A
S A
S A R P 4
P IM -S M 4
R P 1
Join
S ource
S A
S A
P IM -S M 1
R P 3
user
P IM -S M 3
S A m essage
Join
M S D P peers