--- a/doc/tutorial/source/introduction.rst Tue Aug 27 19:08:05 2013 -0700
+++ b/doc/tutorial/source/introduction.rst Wed Aug 28 17:13:51 2013 -0700
@@ -22,21 +22,55 @@
A few key points are worth noting at the onset:
-* Ns-3 is not an extension of `ns-2
+* |ns3| is open-source, and the project strives to maintain an
+ open environment for researchers to contribute and share their software.
+* |ns3| is not a backwards-compatible extension of `ns-2
<http://www.isi.edu/nsnam/ns>`_;
it is a new simulator. The two simulators are both written in C++ but
|ns3| is a new simulator that does not support the |ns2| APIs. Some
models from |ns2| have already been ported from |ns2| to |ns3|. The
project will continue to maintain |ns2| while |ns3| is being built,
and will study transition and integration mechanisms.
-* |ns3| is open-source, and the project strives to maintain an
- open environment for researchers to contribute and share their software.
+
+About |ns3|
+***********
+
+|ns3| has been developed to provide an open, extensible network simulation
+platform, for networking research and education. In brief, |ns3| provides
+models of how packet data networks work and perform, and provides a
+simulation engine for users to conduct simulation experiments. Some of the
+reasons to use |ns3| include to perform studies that are more difficult
+or not possible to perform with real systems, to study system behavior in
+a highly controllled, reproducible environment, and to learn about how
+networks work. Users will note that the available model set in |ns3|
+focuses on modeling how Internet protocols and networks work, but
+|ns3| is not limited to Internet systems; several users are using
+|ns3| to model non-Internet-based systems.
+Many simulation tools exist for network simulation studies. Below are
+a few distinguishing features of |ns3| in contrast to other tools.
+
+* |ns3| is designed as a set of libraries that can be combined together
+ and also with other external software libraries. While some simulation
+ platforms provide users with a single, integrated graphical user
+ interface environment in which all tasks are carried out, |ns3| is
+ more modular in this regard. Several external animators and
+ data analysis and visualization tools can be used with |ns3|. However,
+ users should expect to work at the command line and with C++ and/or
+ Python software development tools.
+* |ns3| is primarily used on Linux systems, although support exists
+ for FreeBSD, Cygwin (for Windows), and native Windows Visual Studio
+ support is in the process of being developed.
+* |ns3| is not an officially supported software product of any company.
+ Support for |ns3| is done on a best-effort basis on the
+ ns-3-users mailing list.
+
For |ns2| Users
***************
-For those familiar with |ns2|, the most visible outward change when moving to
+For those familiar with |ns2| (a popular tool that preceded |ns3|),
+the most visible outward change when moving to
|ns3| is the choice of scripting language. Programs in |ns2| are
scripted in OTcl and results of simulations can be visualized using the
Network Animator nam. It is not possible to run a simulation
@@ -57,17 +91,38 @@
as we proceed in this tutorial.
A question that we often hear is "Should I still use |ns2| or move to
-|ns3|?" The answer is that it depends. |ns3| does not have
-all of the models that |ns2| currently has, but on the other hand, |ns3|
-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.). |ns2|
-models can sometimes be ported to |ns3| (a porting guide is under
-development). The support available on the user mailing list, and the
-developer and maintainer activity, is higher for |ns3|. A good guideline
-would be to look at both simulators, and in particular the models available
-for your research, but when in doubt or when starting new simulation
-projects, choose the tool that is under more active development (|ns3|).
+|ns3|?" In this author's opinion, unless the user is somehow vested
+in |ns2| (either based on existing personal comfort with and knowledge
+of |ns2|, or based on a specific simulation model that is only available
+in |ns2|), a user will be more productive with |ns3| for the following
+reasons:
+
+* |ns3| is actively maintained with an active, responsive users mailing
+ list, while |ns2| is only lightly maintained and has not seen
+ significant development in its main code tree for over a decade.
+* |ns3| provides features not available in |ns2|, such as a implementation
+ code execution environment (allowing users to run real implementation
+ code in the simulator)
+* |ns3| provides a lower base level of abstraction compared with |ns2|,
+ allowing it to align better with how real systems are put together.
+ Some limitations found in |ns2| (such as supporting multiple types of
+ interfaces on nodes correctly) have been remedied in |ns3|.
+
+|ns2| has a more diverse set of contributed modules than does |ns3|, owing to
+its long history. However, |ns3| has more detailed models in several
+popular areas of research (including sophisticated LTE and WiFi models),
+and its support of implementation code admits a very wide spectrum
+of high-fidelity models. Users may be surprised to learn that the
+whole Linux networking stack can be encapsulated in an |ns3| node,
+using the Direct Code Execution (DCE) framework. |ns2|
+models can sometimes be ported to |ns3|, particularly if they have been
+implemented in C++.
+
+If in doubt, a good guideline would be to look at both simulators (as
+well as other simulators), and in particular the models available
+for your research, but keep in mind that your experience may be better
+in using the tool that is being actively developed and
+maintained (|ns3|).
Contributing
************