What is a PIM-SM Rendezvous Point (RP)?
PIM-SM requires at least one Rendezvous Point, or RP, per domain to function. Initially, receivers do not need to know the location of a source to function, as the address of the RP is distributed throughout the domain. When a receiver wants to join a group, G, it sends a IGMP member report to its first hop router, which sends a (*,G) join to the RP. (In case there is more than one first hop router, one is elected to be the Designated Router, or DR, and it carries out this task.) Similarly, when a source wants to begin transmitting to a group, its DR encapsulates and unicasts the multicast data to the RP, which strips off the encapsulation and multicasts it to the group members (if any). Note that the RP is always a router, while a source is a computer attached to a router, so that in general an RP is not a source directly. • What is a Shared Tree (ST), and a Shortest Path Tree (SPT) ? The Shared Tree (also known as the Core Based Tree, or CBT, from the different routing protocol descr
