Software-Defined Networking (SDN) has revolutionized the networking field by addressing scalability, flexibility, and control mechanism issues, which are present in Traditional Networks. One of the major advantages of SDN over Traditional Networks is centralized control over the network. In Traditional Networks, no separate Control Layer is present, due to which configuration and management of the network become extremely difficult. SDN introduces a separate Control Layer, which makes network management an easy and reliable process. Network management is now flexible and does not require expensive hardware and configuration changes. From this, not only the network administrator but also the network intruder benefits. SDN separates the Control and Data Plane of the Network. Due to the separation of the Control Plane, DoS/DDoS attacks on SDN Controller can cause a Single Point of Failure of the entire network, and hence security becomes vital for SDN. In this paper, the security challenges of all three layers of SDN, and solutions that need to be taken by the network administrator has been discussed. Various key benefits of SDN Security has been discussed in this paper. SDN security remains one of the hot topics in the field of networking, and our main goal remains to review the major security advancements, with their scope and limitations.