中文摘要：

随着Internet的迅速发展，网络安全问题日益突出，其中分布式拒绝服务（DDoS）攻击对Internet构成巨大威胁。在分析DDoS攻击机理的基础上，对攻击和防御机制进行分类，以便有效地分析、认识分布式拒绝服务攻击行为。

英文摘要：

With the developing of Internet, network security is becoming more and more critical. Distributed Denial of Service （DDoS） attacks are an immense threat to the Internet. This paper introduces the mechanisms of DDoS attacks, and proposes a taxonomy of DDoS attacks and defense mechanisms, which can analyze and understand DDoS attack behavior effectively.