28Multicast Source Discovery Protocol(MSDP)Multicast source discovery protocol (MSDP) is supported on Dell Networking OS.Protocol OverviewMSDP is a Layer 3 protocol that connects IPv4 protocol-independent multicast-sparse mode (PIM-SM)domains. A domain in the context of MSDP is a contiguous set of routers operating PIM within a commonboundary defined by an exterior gateway protocol, such as border gateway protocol (BGP).Each rendezvous point (RP) peers with every other RP via the transmission control protocol (TCP).Through this connection, peers advertise the sources in their domain.1. When an RP in a PIM-SM domain receives a PIM register message from a source, it sends a source-active (SA) message to MSDP peers, as shown in the following illustration.2. Each MSDP peer receives and forwards the message to its peers away from the originating RP.3. When an MSDP peer receives an SA message, it determines if there are any group members withinthe domain interested in any of the advertised sources. If there are, the receiving RP sends a joinmessage to the originating RP, creating a shortest path tree (SPT) to the source.Multicast Source Discovery Protocol (MSDP) 553
