The Virtual InterNetwork Testbed (VINT) project has enhanced its network simulator, ns, to provide practical innovations that broaden the conditions under which researchers can evaluate network protocols. The rapid growth of the Internet has spurred the development of new protocols and algorithms, but the use of custom simulators, wide-area testbeds, and small-scale lab evaluations has limitations. VINT's ns simulator offers several advantages, including improved validation of existing protocols, a rich infrastructure for developing new protocols, the ability to study large-scale protocol interactions in a controlled environment, and easier comparison of results across research efforts. The simulator supports multiple levels of abstraction, allowing researchers to balance performance and accuracy. Emulation capabilities enable live network traffic to pass through the simulator, providing a powerful tool for evaluating dynamic protocol behavior. The VINT project has also developed ns to support automatic scenario generation and a split-programming model that separates low-level event processing from high-level configuration, enhancing flexibility and productivity. Despite its benefits, ns has a steep learning curve, and future challenges include integrating user contributions, reducing the learning curve, and developing tools for large-scale simulations and newer research areas.The Virtual InterNetwork Testbed (VINT) project has enhanced its network simulator, ns, to provide practical innovations that broaden the conditions under which researchers can evaluate network protocols. The rapid growth of the Internet has spurred the development of new protocols and algorithms, but the use of custom simulators, wide-area testbeds, and small-scale lab evaluations has limitations. VINT's ns simulator offers several advantages, including improved validation of existing protocols, a rich infrastructure for developing new protocols, the ability to study large-scale protocol interactions in a controlled environment, and easier comparison of results across research efforts. The simulator supports multiple levels of abstraction, allowing researchers to balance performance and accuracy. Emulation capabilities enable live network traffic to pass through the simulator, providing a powerful tool for evaluating dynamic protocol behavior. The VINT project has also developed ns to support automatic scenario generation and a split-programming model that separates low-level event processing from high-level configuration, enhancing flexibility and productivity. Despite its benefits, ns has a steep learning curve, and future challenges include integrating user contributions, reducing the learning curve, and developing tools for large-scale simulations and newer research areas.