The growth of “distributed denial-of-service” attacks has become one of the most serious threats to Internet security in recent years. They are classified as serious and have the potential to disrupt network operations. In a short length of time, a “Distributed Denial of Service (DDoS)” assault can overwhelm a victim's computer and communication resources. Many defense systems have been evolved due to the seriousness of the situation. For years, network availability has been harmed by “denial-of-service” attacks, often known as DDoS. Despite multiple warnings, the attack continues to be quite successful. In this paper, we'll look at approaches for detecting “distributed denial of service” attacks in SDN, however, there are two novel DDoS detection algorithms to look for. The first method employs the degree of the attack in order to detect it. The “K-Nearest Neighbors algorithm” is used in the other technique to detect it.