The multicast pattern is characterized by:

The multicast pattern is fundamentally defined by its one-way communication model, where a single sender transmits a message to multiple receivers simultaneously. This allows for efficient distribution of data or commands to multiple endpoints without the need for individual messaging to each receiver. The sender does not wait for responses, making this pattern ideal for scenarios where broadcast-like functionality is required, such as in notifications, updates, or broadcasts where acknowledgments from each receiver are not necessary.

The other options do not capture the essence of the multicast pattern. For instance, the first choice involves receiving responses, which contradicts the one-way aspect of multicast. The aggregation of responses relates to a different pattern—such as the scatter-gather pattern—where responses from multiple services are collected. Lastly, direct point-to-point messaging implies a one-to-one communication method, which is opposite to the group communication nature of the multicast pattern. Hence, the definition that encapsulates the essence of multicast communication is indeed one-way communication from the sender to a group of receivers.