Dell EMC SmartFabric OS10 User Guide Release 10.5.0

Advantages of PIM-SSM

Advantages of PIM-SSM include the following:

• PIM-SSM forwards multicast traffic from a single source to a subnet. Other versions of PIM requires the receiver to subscribe to a group. The receiver receives traffic not just from the source that it is interested in, but from all the sources that send to that group. PIM-SSM requires the receiver to specify the sources in which they are interested in to avoid receiving unnecessary traffic.

• PIM-SSM is more efficient than PIM-SM because it immediately creates shortest path trees (SPT) to the source rather than using shared trees. PIM-SM requires a shared tree rooted at the RP because IGMPv2 receivers do not express the source information in their membership reports. Multicast traffic passes from the source to the receiver through the RP, until the last hop router (LHR) learns the source address, at which point it switches to the SPT.

  PIM-SSM uses IGMPv3. Because receivers subscribe to a source and group, the RP and shared tree are unnecessary; only SPTs are used. On OS10 systems, it is possible to use PIM-SM with IGMPv3 to achieve the same result, but PIM-SSM eliminates the unnecessary protocol overhead.