DDoS attacks constitute one of the major intimidating hardest security problems facing today's Internet. The goal is to flood the victim with overwhelming amounts of traffic, with the purpose of preventing legitimate users from using a victim computing system or network resources. Irrespective of the security features incorporated in the victim system, the acceptable level of security depends on the state of security in the rest of the global Internet. To enhance the overall security against DDoS attack, a cooperative defense mechanism will be the constructive solution. This paper proposes one such effective cooperative multilayer defense mechanism. Unlike other existing systems, our system is capable of handling various forms of DoS attacks. Providing mitigation either at source end or at victim end may not be a complete solution in contrast, our multilayer mitigation is active at both ends. The spoofing and high rate flooding attacks are limited at the source end by implementing comprehensive approach at the network layer and low rate flooding attack at the victim end by implementing Similarity based mechanism at the application layer simultaneously. The performance of the multilayer defense mechanism is validated through extensive simulation in NS-2. The real data sets are used for our analysis and the experimental results show that our scheme can efficiently detect DDoS.