@c ======================================================================== @c Begin document body here @c ======================================================================== @c ======================================================================== @c PART: Introduction @c ======================================================================== @c The below chapters are under the major heading "Introduction" @c This is similar to the Latex \part command @c @c ======================================================================== @c Introduction @c ======================================================================== @node Introduction @chapter Introduction @menu * For ns-2 Users:: * Contributing:: * Tutorial Organization:: @end menu The @command{ns-3} simulator is a discrete-event network simulator targeted primarily for research and educational use. The @uref{http://www.nsnam.org,,ns-3 project}, started in 2006, is an open-source project developing @command{ns-3}. Primary documentation for the @command{ns-3} project is available in four forms: @itemize @bullet @item @uref{http://www.nsnam.org/doxygen/index.html,,ns-3 Doxygen/Manual}: Documentation of the public APIs of the simulator @item Tutorial (this document) @item @uref{http://www.nsnam.org/docs/manual.html,,Reference Manual}: Reference Manual @item @uref{http://www.nsnam.org/wiki/index.php,, ns-3 wiki} @end itemize The purpose of this tutorial is to introduce new @command{ns-3} users to the system in a structured way. It is sometimes difficult for new users to glean essential information from detailed manuals and to convert this information into working simulations. In this tutorial, we will build several example simulations, introducing and explaining key concepts and features as we go. As the tutorial unfolds, we will introduce the full @command{ns-3} documentation and provide pointers to source code for those interested in delving deeper into the workings of the system. A few key points are worth noting at the onset: @itemize @bullet @item Ns-3 is not an extension of @uref{http://www.isi.edu/nsnam/ns,,ns-2}; it is a new simulator. The two simulators are both written in C++ but @command{ns-3} is a new simulator that does not support the ns-2 APIs. Some models from ns-2 have already been ported from ns-2 to @command{ns-3}. The project will continue to maintain ns-2 while @command{ns-3} is being built, and will study transition and integration mechanisms. @item @command{Ns-3} is open-source, and the project strives to maintain an open environment for researchers to contribute and share their software. @end itemize @node For ns-2 Users @section For ns-2 Users For those familiar with ns-2, the most visible outward change when moving to @command{ns-3} is the choice of scripting language. Ns-2 is scripted in OTcl and results of simulations can be visualized using the Network Animator @command{nam}. It is not possible to run a simulation in ns-2 purely from C++ (i.e., as a main() program without any OTcl). Moreover, some components of ns-2 are written in C++ and others in OTcl. In @command{ns-3}, the simulator is written entirely in C++, with optional Python bindings. Simulation scripts can therefore be written in C++ or in Python. The results of some simulations can be visualized by @command{nam}, but new animators are under development. Since @command{ns-3} generates pcap packet trace files, other utilities can be used to analyze traces as well. In this tutorial, we will first concentrate on scripting directly in C++ and interpreting results via trace files. But there are similarities as well (both, for example, are based on C++ objects, and some code from ns-2 has already been ported to @command{ns-3}). We will try to highlight differences between ns-2 and @command{ns-3} as we proceed in this tutorial. A question that we often hear is "Should I still use ns-2 or move to @command{ns-3}?" The answer is that it depends. @command{ns-3} does not have all of the models that ns-2 currently has, but on the other hand, @command{ns-3} does have new capabilities (such as handling multiple interfaces on nodes correctly, use of IP addressing and more alignment with Internet protocols and designs, more detailed 802.11 models, etc.). ns-2 models can usually be ported to @command{ns-3} (a porting guide is under development). There is active development on multiple fronts for @command{ns-3}. The @command{ns-3} developers believe (and certain early users have proven) that @command{ns-3} is ready for active use, and should be an attractive alternative for users looking to start new simulation projects. @node Contributing @section Contributing @cindex contributing @command{Ns-3} is a research and educational simulator, by and for the research community. It will rely on the ongoing contributions of the community to develop new models, debug or maintain existing ones, and share results. There are a few policies that we hope will encourage people to contribute to @command{ns-3} like they have for ns-2: @itemize @bullet @item Open source licensing based on GNU GPLv2 compatibility; @item @uref{http://www.nsnam.org/wiki/index.php,,wiki}; @item @uref{http://www.nsnam.org/wiki/index.php/Contributed_Code,,Contributed Code} page, similar to ns-2's popular @uref{http://nsnam.isi.edu/nsnam/index.php/Contributed_Code,,Contributed Code} page; @item @code{src/contrib} directory (we will host your contributed code); @item Open @uref{http://www.nsnam.org/bugzilla,,bug tracker}; @item @command{Ns-3} developers will gladly help potential contributors to get started with the simulator (please contact @uref{http://www.nsnam.org/people.html,,one of us}). @end itemize We realize that if you are reading this document, contributing back to the project is probably not your foremost concern at this point, but we want you to be aware that contributing is in the spirit of the project and that even the act of dropping us a note about your early experience with @command{ns-3} (e.g. "this tutorial section was not clear..."), reports of stale documentation, etc. are much appreciated. @node Tutorial Organization @section Tutorial Organization The tutorial assumes that new users might initially follow a path such as the following: @itemize @bullet @item Try to download and build a copy; @item Try to run a few sample programs; @item Look at simulation output, and try to adjust it. @end itemize As a result, we have tried to organize the tutorial along the above broad sequences of events. @c ======================================================================== @c Resources @c ======================================================================== @node Resources @chapter Resources @menu * The Web:: * Mercurial:: * Waf:: * Development Environment:: * Socket Programming:: @end menu @node The Web @section The Web @cindex www.nsnam.org @cindex documentation @cindex architecture There are several important resources of which any @command{ns-3} user must be aware. The main web site is located at @uref{http://www.nsnam.org} and provides access to basic information about the @command{ns-3} system. Detailed documentation is available through the main web site at @uref{http://www.nsnam.org/documents.html}. You can also find documents relating to the system architecture from this page. There is a Wiki that complements the main @command{ns-3} web site which you will find at @uref{http://www.nsnam.org/wiki/}. You will find user and developer FAQs there, as well as troubleshooting guides, third-party contributed code, papers, etc. @cindex mercurial repository @cindex ns-3-dev repository @cindex release repository The source code may be found and browsed at @uref{http://code.nsnam.org/}. There you will find the current development tree in the repository named @code{ns-3-dev}. Past releases and experimental repositories of the core developers may also be found there. @node Mercurial @section Mercurial 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. The Concurrent Version System (CVS) is probably the most well known. @cindex software configuration management @cindex Mercurial The @command{ns-3} project uses Mercurial as its source code management system. Although you do not need to know much about Mercurial in order to complete this tutorial, we recommend becoming familiar with Mercurial and using it to access the source code. Mercurial has a web site at @uref{http://www.selenic.com/mercurial/}, from which you can get binary or source releases of this Software Configuration Management (SCM) system. Selenic (the developer of Mercurial) also provides a tutorial at @uref{http://www.selenic.com/mercurial/wiki/index.cgi/Tutorial/}, and a QuickStart guide at @uref{http://www.selenic.com/mercurial/wiki/index.cgi/QuickStart/}. You can also find vital information about using Mercurial and @command{ns-3} on the main @command{ns-3} web site. @node Waf @section Waf @cindex Waf @cindex make @cindex build 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 @code{make}. Along with being the most well known, @code{make} is probably the most difficult to use in a very large and highly configurable system. Because of this, many alternatives have been developed. Recently these systems have been developed using the Python language. The build system @code{Waf} is used on the @command{ns-3} project. It is one of the new generation of Python-based build systems. You will not need to understand any Python to build the existing @command{ns-3} system, and will only have to understand a tiny and intuitively obvious subset of Python in order to extend the system in most cases. For those interested in the gory details of Waf, the main web site can be found at @uref{http://code.google.com/p/waf/}. @node Development Environment @section Development Environment @cindex C++ @cindex Python As mentioned above, scripting in @command{ns-3} is done in C++ or Python. As of ns-3.2, most of the @command{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 an almost unimaginable 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, @uref{http://www.cplusplus.com/doc/tutorial/,,this tutorial}. @cindex toolchain @cindex GNU The @command{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, @uref{http://en.wikipedia.org/wiki/GNU_toolchain}. @command{ns-3} uses gcc, GNU binutils, and gdb. However, we do not use the GNU build system tools, neither make nor autotools. We use Waf for these functions. @cindex Linux Typically an @command{ns-3} author will work in Linux or a Linux-like environment. For those running under Windows, there do exist environments which simulate the Linux environment to various degrees. The @command{ns-3} project supports development in the Cygwin environment for these users. See @uref{http://www.cygwin.com/} for details on downloading (MinGW is presently not officially supported, although some of the project maintainers to work with it). Cygwin provides many of the popular Linux system commands. It can, however, sometimes be problematic due to the way it actually does its emulation, and sometimes interactions with other Windows software can cause problems. @cindex Cygwin @cindex MinGW If you do use Cygwin or MinGW; and use Logitech products, we will save you quite a bit of heartburn right off the bat and encourage you to take a look at the @uref{http://oldwiki.mingw.org/index.php/FAQ,,MinGW FAQ}. @cindex Logitech Search for ``Logitech'' and read the FAQ entry, ``why does make often crash creating a sh.exe.stackdump file when I try to compile my source code.'' Believe it or not, the @code{Logitech Process Monitor} insinuates itself into every DLL in the system when it is running. It can cause your Cygwin or MinGW DLLs to die in mysterious ways and often prevents debuggers from running. Beware of Logitech software when using Cygwin. Another alternative to Cygwin is to install a virtual machine environment such as VMware server and install a Linux virtual machine. @node Socket Programming @section Socket Programming @cindex sockets 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 @uref{http://www.elsevier.com/wps/find/bookdescription.cws_home/717656/description#description,,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: @uref{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, @uref{http://www.elsevier.com/wps/find/bookdescription.cws_home/700736/description#description,,Multicast Sockets, Makofske and Almeroth}. that covers material you may need to understand if you look at the multicast examples in the distribution.