MSDP essentially connects PIM-SM domains beyond the borders of autonomous systems. MSDP in combination with MBGP can connect easily multicast-enabled ISP domains at private or public peering points by maintaining their individual RPs. MSDP is also a key enabler for anycast RPs. Anycast RPs add load sharing and redundancy to PIM-SM multicast networks. The MSDP peering connection is implemented in TCP, whereas PIM-SM takes care of the actual forwarding between domains.