Users Guide

Multicast Source Discovery Protocol (MSDP)
Multicast source discovery protocol (MSDP) is supported on Dell Networking OS.
Protocol Overview
MSDP 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 common boundary 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 within the domain interested in any of the
advertised sources. If there are, the receiving RP sends a join message to the originating RP, creating a shortest path tree (SPT) to
the source.
Figure 81. Multicast Source Discovery Protocol (MSDP)
RPs advertise each (S,G) in its domain in type, length, value (TLV) format. The total number of TLVs contained in the SA is indicated in
the “Entry Count” field. SA messages are transmitted every 60 seconds, and immediately when a new source is detected.
31
468 Multicast Source Discovery Protocol (MSDP)