Resources¶
The Web¶
There are several important resources of which any ns-3 user must be aware. The main web site is located at https://www.nsnam.org and provides access to basic information about the ns-3 system. Detailed documentation is available through the main web site at https://www.nsnam.org/documentation/. You can also find documents relating to the system architecture from this page.
There is a Wiki that complements the main ns-3 web site which you will find at https://www.nsnam.org/wiki/. You will find user and developer FAQs there, as well as troubleshooting guides, third-party contributed code, papers, etc.
The source code may be found and browsed at GitLab.com:
https://gitlab.com/nsnam/.
There you will find the current development tree in the repository named
ns-3-dev. Past releases and experimental repositories of the core
developers may also be found at the project’s old Mercurial site at
http://code.nsnam.org.
Git¶
Complex software systems need some way to manage the organization and changes to the underlying code and documentation. There are many ways to perform this feat, and you may have heard of some of the systems that are currently used to do this. Until recently, the ns-3 project used Mercurial as its source code management system, but in December 2018, switch to using Git. Although you do not need to know much about Git in order to complete this tutorial, we recommend becoming familiar with Git and using it to access the source code. GitLab.com provides resources to get started at: https://docs.gitlab.com/ee/gitlab-basics/.
CMake¶
Once you have source code downloaded to your local system, you will need
to compile that source to produce usable programs. Just as in the case of
source code management, there are many tools available to perform this
function. Probably the most well known of these tools is make. Along
with being the most well known, make is probably the most difficult to
use in a very large and highly configurable system. Because of this, many
alternatives have been developed.
The build system CMake is used on the ns-3 project.
For those interested in the details of CMake, the CMake documents are available at https://cmake.org/cmake/help/latest/index.html and the current code at https://gitlab.kitware.com/cmake/cmake.
Development Environment¶
As mentioned above, scripting in ns-3 is done in C++ or Python. Most of the ns-3 API is available in Python, but the models are written in C++ in either case. A working knowledge of C++ and object-oriented concepts is assumed in this document. We will take some time to review some of the more advanced concepts or possibly unfamiliar language features, idioms and design patterns as they appear. We don’t want this tutorial to devolve into a C++ tutorial, though, so we do expect a basic command of the language. There are a wide number of sources of information on C++ available on the web or in print.
If you are new to C++, you may want to find a tutorial- or cookbook-based book or web site and work through at least the basic features of the language before proceeding. For instance, this tutorial.
On Linux, the ns-3 system uses several components of the GNU “toolchain” for development. A software toolchain is the set of programming tools available in the given environment. For a quick review of what is included in the GNU toolchain see, http://en.wikipedia.org/wiki/GNU_toolchain. ns-3 uses gcc, GNU binutils, and gdb. However, we do not use the GNU build system tools, neither make directly. We use CMake for these functions.
On macOS, the toolchain used is Xcode. ns-3 users on a Mac are strongly encouraged to install Xcode and the command-line tools packages from the Apple App Store, and to look at the ns-3 installation wiki for more information (https://www.nsnam.org/wiki/Installation).
Typically an ns-3 author will work in Linux or a Unix-like environment. For those running under Windows, there do exist environments which simulate the Linux environment to various degrees. The ns-3 project has in the past (but not presently) supported development in the Cygwin environment for these users. See http://www.cygwin.com/ for details on downloading, and visit the ns-3 wiki for more information about Cygwin and ns-3. MinGW is presently not officially supported. Another alternative to Cygwin is to install a virtual machine environment such as VMware server and install a Linux virtual machine.
Socket Programming¶
We will assume a basic facility with the Berkeley Sockets API in the examples used in this tutorial. If you are new to sockets, we recommend reviewing the API and some common usage cases. For a good overview of programming TCP/IP sockets we recommend TCP/IP Sockets in C, Donahoo and Calvert.
There is an associated web site that includes source for the examples in the book, which you can find at: http://cs.baylor.edu/~donahoo/practical/CSockets/.
If you understand the first four chapters of the book (or for those who do not have access to a copy of the book, the echo clients and servers shown in the website above) you will be in good shape to understand the tutorial. There is a similar book on Multicast Sockets, Multicast Sockets, Makofske and Almeroth. that covers material you may need to understand if you look at the multicast examples in the distribution.