Performing realistic simulations of Internet packet traffic on a national or global level is a daunting task from both the modeling and the computational perspective. We present the MIITS (Multi-scale Integrated Information and Telecommunications System) tool that implements a novel approach to network simulation and report first scaling results from a realistic Internet scenario. MIITS' end-to-end approach to network simulation relies on modules for (i) accurate network topology and capacity representation, (ii) realistic communication session generation based on the activities of an agent population that is statistically equivalent to the population in a large metropolitan area, (iii) the actual scalable packet-level network simulation that is based on distributed event-driven technology, and (iv) analysis of large amounts of simulation output data. We present a sample simulation of a Los Angeles network as an intermediate step toward the vision of national-level simulation.