Distributed Denial of Service (DDoS) attacks are attempts to overwhelm a computer system in order to deny access by legitimate users. They are generally unstoppable, but there is a good deal of on-going research on methods to reduce their negative effects. This paper will deal with the design of a model that simulates such an attack. The simulation model is then used to study possible ways to defend against these attacks. Three experiments are run: 1) using a priority queue to sort messages from clients based on how many connections they have open on the server; 2) limiting the number of...