This paper presents a comprehensive study on the implementation of a Denial of Service (DOS) attack using NS2, a widely-used network simulator. The project involves the installation and configuration of NS2 and NAM on Ubuntu, the design of a realistic network topology, and the generation of TCP and UDP traffic to simulate a DOS attack. By evaluating the impact of the attack on network performance metrics such as throughput and latency, this study aims to enhance understanding of DOS attacks in simulated environments and propose effective mitigation strategies. The findings contribute to the field of network security by providing insights into the behavior of DOS attacks and highlighting the importance of proactive defense mechanisms.