DescriptionModeling and simulation play a key role in analyzing the impact of system design choices on applications' communication performance. The HPC community currently offers several predictive design tools with varying focus and strengths. To make the best use of these tools, it is critical that the tool developers and end users interact to identify the user requirements and capabilities of these tools. In this BoF, we will discuss recent advances in modeling and simulation techniques and identify opportunities for cross-pollination among various predictive design techniques. We will also discuss the requirements and challenges posed by the end users.