"The open source network simulation tool ns-2 is an invaluable tool for researchers working on wired or wireless networks. I came across ns-2 while working on my thesis. I needed a network simulator, and since my college lacked the brand-name heavyweights, I had to look for an alternative that was free but could do the job. While ns-2 is free, it's also pretty unfriendly.
"ns-2 is a variant of the REAL network simulator. Over the past few years it has been evolving, and it is still far from complete. Several organizations have been involved in its development, including DARPA, Xerox, UCB, and Sun Microsystems. The objective has been to make a network simulation tool to study and analyze new ideas in detail before implementation..."
