unison/doc/tutorial/introduction.texi

@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 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 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 ns-3. The project will
continue to maintain ns-2 while 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 typically 
scripted in Tcl and results of simulations can be visualized using the 
Network Animator @command{nam}.  In @command{ns-3} there is currently no
visualization module, and Python bindings have been developed (Tcl bindings
have been prototyped using @uref{http://www.swig.org,,SWIG}, but are not 
currently supported).  In this tutorial, we will 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.

@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  

If you are an ns-3 user, please consider providing your feedback, bug fixes, or
code to the project.  

@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 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 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 will 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 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://freehackers.org/~tnagy/waf.html}.

@node Development Environment
@section Development Environment

@cindex C++
As mentioned above, scripting in ns-3 is done in C++.  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.

@cindex toolchain
@cindex GNU
The @command{ns-3} system uses 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}.

@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 and the MinGW environments for 
these users.  See @uref{http://www.cygwin.com/} and 
@uref{http://www.mingw.org/} for details on downloading and using these
systems.  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://www.mingw.org/MinGWiki/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.

@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/product/cws_home/680765,,Practical 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/product/cws_home/700736,,Multicast Sockets, Makofske and Almeroth}.
that covers material you may need to understand if you look at the multicast 
examples in the distribution.