Which Multicast Routing Mechanism is Optimal for Many-to-Many Multicast Applications?

D.

The optimal multicast routing mechanism to support many-to-many multicast applications is BIDIR-PIM (Bidirectional Protocol Independent Multicast). Therefore, the correct answer is D.

Here's a brief explanation of the different multicast routing protocols and why BIDIR-PIM is the optimal choice:

1. PIM-SM (Protocol Independent Multicast - Sparse Mode): This protocol is used when there are a small number of receivers for a multicast group, and the data needs to be routed efficiently across a sparsely populated network. PIM-SM uses a shared tree approach where a single tree is used to forward multicast traffic to all the receivers. This approach works well when there are few receivers but becomes inefficient when there are many receivers, as the shared tree can become overloaded.

2. MOSPF (Multicast Open Shortest Path First): MOSPF is a protocol used in conjunction with OSPF (Open Shortest Path First) to build multicast trees in a network. MOSPF is not commonly used today, as it has been replaced by PIM.

3. DVMRP (Distance Vector Multicast Routing Protocol): DVMRP is a multicast routing protocol that uses the distance-vector algorithm to forward multicast traffic. It is an older protocol and is not commonly used today.

4. BIDIR-PIM (Bidirectional Protocol Independent Multicast): BIDIR-PIM is designed to efficiently support many-to-many multicast applications. It uses a shared tree for upstream traffic and a separate tree for downstream traffic. This approach is more efficient than PIM-SM for many-to-many applications because it eliminates the need for routers to maintain large multicast routing tables.

5. MSDP (Multicast Source Discovery Protocol): MSDP is used to connect multiple PIM-SM domains to support inter-domain multicast traffic. MSDP is not a multicast routing protocol, but rather a mechanism for exchanging information about active multicast sources between different PIM-SM domains.

In summary, while PIM-SM is a widely used multicast routing protocol, it is not optimal for many-to-many multicast applications. BIDIR-PIM is the optimal protocol for these types of applications, as it uses a shared tree for upstream traffic and a separate tree for downstream traffic, eliminating the need for large multicast routing tables.