Network Denial-of-Service (N-DoS) attacks are one of the fastest growing types of attack on the Internet. This paper addresses the vulnerabilities in Internet protocols, as well as deficiencies in flowcontrol in the Internet, both of which contribute to the loss of resource availability when networks suffer N-DoS attacks. Furthermore, an AFFC (Anti-flooding Flow-Control) model is presented to defend against flooding N-DoS attacks. AFFC policies regulate unresponsive elastic traffic and aggressive best-effort traffic for specific flow classes. Experiments have demonstrated that the deployment of this model can thwart harmful flows and prevent congestion collapse by flooding N-DoS attacks.