ns3 software package provides discrete-event network simulator for Internet systems, you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install ns3
ns3 is installed in your system.
Make ensure the ns3 package were installed using the commands given below,
$ sudo dpkg-query -l | grep ns3 *
You will get with ns3 package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | Network |
| Package | ns3 |
| Version | 3.17+dfsg-1build1 |
| Description | discrete-event network simulator for Internet systems |
| Sub Section | Net |