1. Quick Start

This section is optional, for readers who want to get ns-3 up and running as quickly as possible. Readers may skip forward to the Introduction chapter, followed by the Getting Started chapter, for a lengthier coverage of all of this material.

1.1. Brief Summary

ns-3 is a discrete-event simulator typically run from the command line. It is written directly in C++, not in a high-level modeling language; simulation events are simply C++ function calls, organized by a scheduler.

An ns-3 user will obtain the ns-3 source code (see below), compile it into shared (or static) libraries, and link the libraries to main() programs that he or she authors. The main() program is where the specific simulation scenario configuration is performed and where the simulator is run and stopped. Several example programs are provided, which can be modified or copied to create new simulation scenarios. Users also often edit the ns-3 library code (and rebuild the libraries) to change its behavior.

ns-3 has optional Python bindings for authoring scenario configuration programs in Python (and using a Python-based workflow); this quick start does not cover those aspects.

1.2. Prerequisites

ns-3 has various optional extensions, but the main features just require a C++ compiler (g++ or clang++), Python (version 3.6 or above), CMake and a build-system (e.g. make, ninja, Xcode). We focus in this chapter only on getting ns-3 up and running on a system supported by a recent C++ compiler and Python runtime support.

For Linux, use either g++ or clang++ compilers. For macOS, use clang++ (available in Xcode or Xcode Command Line Tools). For Windows, Msys2 tools with the MinGW64 toolchain can be used (since ns-3.37) for most use cases. For releases earlier than ns-3.37, or for use of emulation modes or Python bindings, we recommend to either use a Linux virtual machine, or the Windows Subsystem for Linux.

1.3. Downloading ns-3

ns-3 is distributed in source code only (some binary packages exist but they are not maintained by the open source project). There are two main ways to obtain the source code: 1) downloading the latest release as a source code archive from the main ns-3 web site, or 2) cloning the Git repository from GitLab.com. These two options are described next; either one or the other download option (but not both) should be followed.

1.3.1. Downloading the Latest Release

  1. Download the latest release from https://www.nsnam.org/releases/latest

  2. Unpack it in a working directory of your choice.

    $ tar xjf ns-allinone-3.40.tar.bz2
  3. Change into the ns-3 directory directly; e.g.

    $ cd ns-allinone-3.40/ns-3.40

The ns-allinone directory has some additional components but we are skipping over them here; one can work directly from the ns-3 source code directory. The rest of the tutorial describes the additional components.

1.3.2. Cloning ns-3 from GitLab.com

You can perform a Git clone in the usual way:

$ git clone https://gitlab.com/nsnam/ns-3-dev.git

If you are content to work with the tip of the development tree; you need only to cd into ns-3-dev; the master branch is checked out by default.

$ cd ns-3-dev

If instead you want to try the most recent release (version 3.40 as of this writing), you can checkout a branch corresponding to that git tag:

$ git checkout -b ns-3.40-branch ns-3.40

1.4. Building and testing ns-3

Once you have obtained the source either by downloading a release or by cloning a Git repository, the next step is to configure the build using the CMake build system. The below commands make use of a Python wrapper around CMake, called ns3, that simplifies the command-line syntax, resembling Waf syntax. There are several options to control the build, but enabling the example programs and the tests, for a default build profile (with asserts enabled and and support for ns-3 logging) is what is usually done at first:

$ ./ns3 configure --enable-examples --enable-tests

Then, use ns3 to build ns-3:

$ ./ns3 build

Once complete, you can run the unit tests to check your build:

$ ./test.py

All tests should either PASS or be SKIPped. At this point, you have a working ns-3 simulator. From here, you can start to run programs (look in the examples directory). To run the first tutorial program, whose source code is located at examples/tutorial/first.cc, use ns3 to run it (by doing so, the ns-3 shared libraries are found automatically):

$ ./ns3 run first

To view possible command-line options, specify the –PrintHelp argument:

$ ./ns3 run 'first --PrintHelp'

To continue reading about the conceptual model and architecture of ns-3, the tutorial chapter Conceptual Overview would be the next natural place to skip to, or you can learn more about the project and the various build options by continuing directly with the Introduction and Getting Started chapters.