For start-up learner, it can be a little playground where your can set up your own network scenario and topology, like how many nodes you want to put there as well as the distances between them, what layers they are working on and customize parameters like their transfer rate and delay etc to schedule events...by digging into the logs after experiment, you can have an overall sight on what is going on in that network layout. Great way to get in touch with those popular devices and protocols in a simulated environment. For experienced engineer or developers, ns-3 is a comprehensive and powerful platform to choose when you want to implement or realize your theory and design. For example, if you want to implement a new protocol and see how it work in practical use, you can either edict existing protocols or rewrite a new protocol suite, then make it compatible with others and embed them into devices which refers to object "node" in ns-3...great platform for computer network research!

The software provides you network bandwidth simulation