SDN is a pivotal technology that relies on the fundamental idea of decoupling control and data planes in the network. This property provides several advantages such as flexibility, simplification, and lower costs. However, it also brings several drawbacks that are largely induced by the centralized control paradigm. Security is one of the most significant challenges related to centralization. In that regard, DDoS attacks are particularly pertinent to the SDN environment. This article presents a concise survey on solutions against DDoS attacks in software-defined networks. Moreover, several mechanisms are analyzed, and a comparative classification is provided for rendering the current state of the art in the literature. This analysis will help researchers to address weaknesses of these solutions and thus mitigate such attacks using more effective defense mechanisms.