Network simulations with ns-3

This repository contains slides and some code samples from my GCC presentation, given on 2020 November 24 at 5:30pm EST.

Abstract

Over the past semester, I've been working with ns-3 in an attempt to reproduce a simulation study for an algorithm that was designed to replicate data efficiently in highly-partitioned mobile ad hoc networks. While I have a fair bit of experience with C++, nevertheless, getting started with ns-3 was a lot more challenging than expected. This presentation overviews an introduction to networks, some considerations to keep in mind when designing network simulations, and what you should expect when programming ns-3 "scripts."

I hope that this presentation can provide some historical context that makes it easier to understand some of the quirks of ns-3 programming, and that you will be able to learn from some of my mistakes and struggles which I outline.

Slides

A PDF copy of the slide presentation is included in this repository. The original presentation was created with Google Slides and is located at the following URL:

https://docs.google.com/presentation/d/1dlCj2B-NGzwKvMjamJPFVaxOz79d82rNQosMGwtMBEc/

Code samples

To run each of these code samples, download ns-3 as instructed in the slides. Copy these C++ source files to the scratch/ directory of your distribution. Finally, run each simulation with ./waf --run scratch/$file, where $file is the name of the simulation you want to run.

You can visualize most of these simulations by adding the --vis flag to the waf run command.

Each simulation will produce an XML file in the animations/ directory adjacent to scratch/. These XML files can be opened with the NetAnim program, which comes with your ns-3 distribution by default.

See the official documentation at https://nsnam.org for more details.

Mobility model demos

These scripts were used to generate the GIFs that are used on slide 44.

1. mobility-walk2d-bounds.cc

   Demonstrates a mobility model over a 100m x 100m area that looks like energetic particles in a container.

2. mobility-walk2d-time.cc

   Demonstrates a mobility model over a 100m x 100m area that simulates individuals aimlessly wandering over the area.

3. mobility-waypoint.cc

   Demonstrates a simple waypoint model where individuals pick a place to go, wait there for some period of time as if to complete a task, then choose a new destination and repeat. This can be thought of like a town square, where individuals visit vendor stalls.

4. mobility-3d.cc

   Sample code to set up and run a 3D stochastic Gauss-Markov model. As I understand it, this is not supported by either of the visualization tools included with ns-3.32.

5. mobility-walk2d-default.cc

   Demonstrates the (not very useful) defaults for the RandomWalk2dMobilityModel. This creates an effect where nodes have "jitter," moving short distances and changing direction randomly and often. As a result, the nodes do not travel a very distance from their initial position even after running the simulation for a substantial amount of time.

Demos

These scripts were run as demonstrations during the "Demo time" slides. In the first demo period, the first simulation was explained and run. In the second demo period, the second simulation was explained and run.

1. point-to-point.cc

   The "Hello World" of ns-3. This code is based on the examples/tutorial/first.cc program included with the ns-3.32 source distribution. It has been modified to run for a longer period of time and demonstrate more packets sent over the wire.

2. on-off-app.cc

   The "Hello World" of MANET simulations in ns-3. This code runs a short simulation of 32 nodes running an "on-off" application which tries to connect with the first node. Nodes have a 15m radius of connectivity, with DSDV routing. The visualization shows partitions occurring naturally in the network and lag in distributing routing tables by this proactive routing algorithm.

License

The code samples in this repository are free software, made available under the GNU General Public License v2 (GPLv2). See the LICENSE file for more details.

The presentation slides and content are released to the Public Domain, free of copyright restrictions and may be used or remixed as is seen fit. In jurisdictions where public domain copyright law does not allow for free and unrestricted use, to the extent possible under law, I waive all copyrights and related rights to this work under the Creative Commons 0 (CC0) 1.0 Universal License.