This paper presents the design and implementation of the NCTUns 1.0 network simulator, which is a high-fidelity and extensible network simulator capable of simulating both wired and wireless IP networks. By using an enhanced simulation methodology, a new simulation engine architecture, and a distributed and open-system architecture, the NCTUns 1.0 network simulator is much more powerful than its predecessor -- the Harvard network simulator, which was released to the public in 1999. The NCTUns 1.0 network simulator consists of many components. In this paper, we present the design and implementation of these components and their interactions in detail