Which of the following descriptions related to PIM is correct?

Question

Options

• APIM-SSM is widely deployed in enterprises for multicast forwarding.
• BPIM-SSM is applicable to scenarios with known multicast sources.
• CPIM-SM is applicable to scenarios with known multicast sources.
• DPIM-DM is more complex than PIM-SM and is therefore rarely used.

• A
  3% (1)
• B
  79% (26)
• C
  12% (4)
• D
  6% (2)

Explanation

PIM-SSM (Source-Specific Multicast) is designed for scenarios where receivers already know the exact source address of multicast traffic, using (S,G) channel subscriptions rather than relying on a Rendezvous Point. This makes option B correct.

Option A is wrong because PIM-SSM is more commonly deployed in service provider and IPTV environments, not enterprise networks; PIM-SM is the more widely used enterprise multicast protocol. Option C is wrong because it swaps the roles: PIM-SM uses a Rendezvous Point precisely to handle cases where the source is not known in advance, making it suited for unknown-source scenarios, not known-source ones. Option D is wrong on both counts: PIM-DM is actually simpler than PIM-SM (it uses a straightforward flood-and-prune mechanism), and while it is rarely used, the reason is poor scalability and bandwidth waste, not complexity.

Memory tip: Break down the acronym - SSM stands for Source-Specific Multicast, and the word "Specific" tells you the source must be specifically identified (known) beforehand. If you know the Source, use SSM.

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