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MSDP
The Multicast Source Discovery Protocol (MSDP) is used in inter-domain multicast routing to facilitate the sharing of multicast source information between different multicast-enabled routing domains. It enables routers to discover active multicast sources outside their own domain, enhancing the distribution of multicast streams across the internet..
The Multicast Source Discovery Protocol (MSDP) operates between multicast-enabled routers to facilitate the exchange of information regarding active multicast sources. It is primarily implemented in conjunction with Protocol Independent Multicast Sparse Mode (PIM-SM) to enable inter-domain multicast routing. By sharing source information, MSDP allows receivers in different PIM-SM domains to join multicast streams initiated in external domains.
MSDP routers establish TCP peer connections, known as MSDP peers, where they exchange Source-Active (SA) messages encapsulating information about multicast sources currently transmitting traffic. These SA messages enable the receiving routers to update their multicast routing tables and forward join messages efficiently to multicast sources, enabling seamless multicast data flow across multiple administrative boundaries.
Despite its effectiveness, MSDP is often considered complex and legacy, especially with newer protocols like Source-Specific Multicast (SSM) simplifying multicast deployments. Nonetheless, MSDP remains in use within protocols where Any-Source Multicast (ASM) operation is required, especially in larger or legacy networks requiring multicast inter-domain communication.