The widespread adoption of cluster computing systems has shifted the modeling focus from synthetic traffic to realistic workloads to better capture the complex interactions between applications and architecture. In this context, a full-system simulation environment also needs to model the networking component, but the simulation duration that is practically affordable is too short to appropriately stress the networking bottlenecks. In this paper, we present a methodology that overcomes this problem and enables the modeling of interconnection networks while ensuring representative results with fast simulation turnaround. We use standard network tools to extract simplified models that are statistically validated and at the same time compatible with a full system simulation environment. We propose three models with different accuracy vs. speed ratios that compute network latency times according to the estimated traffic and measure them on a real-world parallel scientific application.