What Protocol Independent Multicast (PIM) is designed to support large, densely populated multicast groups?

The correct answer is Dense Mode (DM). This protocol is specifically designed to support large, densely populated multicast groups effectively. Dense Mode operates under the assumption that there are many receivers in a particular multicast group within a network segment, allowing it to send multicast traffic to all links within the network by default.

To achieve efficiency in such environments, it utilizes a flooding approach, initially sending multicast packets to all network segments. If certain parts of the network do not have interested receivers, it prunes those branches and stops sending packets there, which works well in scenarios where multicast group membership is common and receivers are widespread.

This contrasts with Sparse Mode (SM), which is tailored for scenarios where multicast receivers are spread out across a network—ideal for less dense groups. Additionally, Any-Source Multicast (ASM) and Single-Source Multicast (SSM) are terms that relate to different multicast methods but do not directly address the same needs as Dense Mode does when it comes to managing traffic for large, densely populated multicast groups.