ns-3 is a discrete-event network simulator for Internet systems, targeted primarily for research and educational use. ns-3 is free, open-source software, licensed under the GNU GPLv2 license, and maintained by a worldwide community.

ns-3 is the most popular Linux alternative to OMNeT++.
ns-3 is the most popular free alternative to OMNeT++.
- ns-3 is Free and Proprietary


