In recent years, research has shown the networking layer's significant influence on the scalability, security, and privacy of blockchain systems. Such large-scale networks however exhibit a degree of complexity that demands model-based simulations as real-world experiments are often not possible. In this work, we methodically characterize blockchain networks by reference to the paradigmatic Bitcoin peer-to-peer network, explore the state-of-the-art protocols, and emphasize this key design space. To this end, we conducted a longitudinal measurement study on the Bitcoin network, from which we extract a comprehensive network model and implement it as part of the bns network simulation framework. We validate the model in comparison to real-world measurements as well as to results from related work. Moreover, we experimentally show how network utilization and miners' geographical location impact the block propagation characteristics.