NetEm Based Simple Comms Emulator for Docker Networks

This project provides a simple, yet powerful, network emulator using tc (traffic control) and netem (network emulator) to simulate various network conditions between robots. It is particularly useful for testing the resilience of robotic communication links to issues like packet loss, latency, and bandwidth limitations.

This emulator has two main components:

1. InitialSetup: A C++ program that sets up the initial queuing discipline (qdisc) on a specified network device.
2. RobotToRobotCommsEmulator: A C++ program that listens for Gazebo transport messages to dynamically adjust network parameters like packet drop rate, bandwidth, and delay between two specified robots.

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Dependencies

• ignition-transport11: This project requires the ignition-transport11 library for communication.

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Build Instructions

1. Navigate to the build directory:

   cd build

2. Generate the build files with CMake:

   cmake ..

3. Compile the emulator:

   make InitialSetup RobotToRobotCommsEmulator

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How to Use

1. Initial Network Setup

First, you need to run the InitialSetup executable to configure the basic queuing discipline on your chosen network device. This only needs to be done once.

• Usage:

  ./InitialSetup <device> <bands>

• Example: The following command sets up a prio qdisc with 3 bands on the lo (loopback) device. For two robots you need 3 (2+1) bands.

  ./InitialSetup lo 3

2. Emulate Robot-to-Robot Communication Links

To emulate the network link between two robots (or containers), run an instance of the RobotToRobotCommsEmulator. You will need to provide the names of the robots and the corresponding virtual ethernet (veth) interfaces.

• Usage:

  ./RobotToRobotCommsEmulator <robot_name_1> <veth_name_1> <robot_name_2> <veth_name_2>

• Examples:

  • To emulate the link between a robot named atlas and a robot named bestla, run:

    ./RobotToRobotCommsEmulator atlas veth10b88fe bestla veth32a464a

3. How the script Control Network Conditions

Once the RobotToRobotCommsEmulator is running, it subscribes to several Gazebo transport topics to receive commands for adjusting the network conditions. You can publish to these topics to dynamically change the simulated network link. The topics are constructed as follows:

/robot_comms_emu_helper/<source_robot>_to_<target_robot>/<control_type>

Here are the available controls:

• Packet Drop Rate:

  • Topic: /robot_comms_emu_helper/atlas_to_bestla/packet_drop_rate
  • Message Type: gz::msgs::Double
  • Value: A value between 0.0 (0% drop) and 1.0 (100% drop).

• Bandwidth:

  • Topic: /robot_comms_emu_helper/atlas_to_bestla/bandwidth
  • Message Type: gz::msgs::Double
  • Value: Bandwidth in Mbps.

• Delay:

  • Topic: /robot_comms_emu_helper/atlas_to_bestla/delay
  • Message Type: gz::msgs::Double
  • Value: Delay in milliseconds.