Numerous state-of-the-art simulation tools are available for network research. NS-2/3 is the most widely used and highly recognized open-source network simulator among the available simulators. The simulation behavior of NS-2/3 is highly trusted within the research community. It is a dependable and realistic discrete event-based simulator tool that has proven more practical. It is primarily designed to support wired networks based on the OSI model, excluding presentation and session layers. Its wireless extension of NS-2/3 extensively supports wireless networks. It has many available features and has already implemented many external protocols. In this talk, I will discuss the Contribution of NS-2/3 in the research community.