Source Specific Multicast (PIM-SSM)

Copied from packetlife

Source-Specific Multicast (SSM), defined in RFC 4607, extends this concept to identify a set of multicast hosts not only by group address but also by source.

SSM brings several important benefits over ASM. Because an SSM channel is defined by both a source and a group address, group addresses can be re-used by multiple sources while keeping channels unique.

One of the biggest advantages SSM holds over ASM is that it does not rely on the designation of a rendezvous point (RP) to establish a multicast tree.

Reference: http://packetlife.net/
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