Cloud computing has a central role to play in meeting today׳s business requirements. However, Distributed Denial-of-Service (DDoS) attacks can threaten the availability of cloud functionalities. In recent years, many effort has been expended to detect the various DDoS attack types. In this survey paper, our concentration is on how to mitigate these attacks. We believe that cloud computing technology can substantially change the way we respond to a DDoS attack, based on a number of new characteristics, which were introduced with the advent of this technology. We first present a new taxonomy of DDoS mitigation strategies to organize the work. Then, we go on to discuss the main features of existing DDoS mitigation strategies and explain their functionalities in the cloud environment. Afterwards, we show how the existing DDoS mechanisms fit into the network topology of the cloud. Finally, we discuss some of these DDoS mechanisms in detail, and compare their behavior in the cloud. Our objective is to show how these characteristics bring a novel perspective to existing DDoS mechanisms, and so give researchers new insights into how to mitigate DDoS attacks in the cloud computing.