How to Implement Point to Multi point Topology in ns3

To implement a point-to-multipoint topology in ns3, we need to create a network where a single central node (such as a router or switch) is connected to multiple peripheral nodes. This topology is commonly used in various network scenarios, that includes wireless and wired communications. Here are the steps and example code to set up a point-to-multipoint topology in ns3.

Steps to implement point-to-multipoint topology

1. Set Up ns3:
   • Make sure that ns3 is installed in the computer. If not, install it.
2. Create the Nodes:
   • To represent the central node and the peripheral nodes, create a set of nodes.
3. Set Up the Point-to-Point Channels:
   • To connect the central node to each peripheral node, use point-to-point helpers.
4. Install Network Stack:
   • On all nodes, install the internet stack.
5. Assign IP Addresses:
   • To the nodes connected to the point-to-point links, assign IP addresses.
6. Set Up Applications:
   • To generate traffic and demonstrate communication between nodes, install applications.

Example code

Here is an example to set up a basic point-to-multipoint topology in ns3.

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/point-to-point-module.h”

#include “ns3/applications-module.h”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“PointToMultipointTopologyExample”);

int main (int argc, char *argv[])

{

CommandLine cmd;

cmd.Parse (argc, argv);

// Create nodes

NodeContainer centralNode;

centralNode.Create (1); // Create 1 central node

NodeContainer peripheralNodes;

peripheralNodes.Create (4); // Create 4 peripheral nodes

// Create point-to-point links

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute (“DataRate”, StringValue (“5Mbps”));

pointToPoint.SetChannelAttribute (“Delay”, StringValue (“2ms”));

NetDeviceContainer devices;

InternetStackHelper stack;

stack.Install (centralNode);

stack.Install (peripheralNodes);

Ipv4AddressHelper address;

int subnet = 1;

// Connect centralNode to each peripheralNode

for (uint32_t i = 0; i < peripheralNodes.GetN (); ++i)

{

NetDeviceContainer link = pointToPoint.Install (NodeContainer (centralNode.Get (0), peripheralNodes.Get (i)));

devices.Add (link);

std::ostringstream subnetStream;

subnetStream << “10.1.” << subnet++ << “.0”;

address.SetBase (subnetStream.str ().c_str (), “255.255.255.0”);

address.Assign (link);

}

// Enable routing

Ipv4GlobalRoutingHelper::PopulateRoutingTables ();

// Create a UDP server on one of the peripheral nodes

UdpServerHelper udpServer (9);

ApplicationContainer serverApp = udpServer.Install (peripheralNodes.Get (0));

serverApp.Start (Seconds (1.0));

serverApp.Stop (Seconds (10.0));

// Create a UDP client on the central node

UdpClientHelper udpClient (address.GetAddress (0, 0), 9); // IP of the server node

udpClient.SetAttribute (“MaxPackets”, UintegerValue (320));

udpClient.SetAttribute (“Interval”, TimeValue (MilliSeconds (50)));

udpClient.SetAttribute (“PacketSize”, UintegerValue (1024));

ApplicationContainer clientApp = udpClient.Install (centralNode.Get (0));

clientApp.Start (Seconds (2.0));

clientApp.Stop (Seconds (10.0));

// Enable packet capture

pointToPoint.EnablePcapAll (“point-to-multipoint-topology”);

// Enable logging

LogComponentEnable (“UdpClient”, LOG_LEVEL_INFO);

LogComponentEnable (“UdpServer”, LOG_LEVEL_INFO);

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

Explanation

1. Setup:

Created one central node and four peripheral nodes connected by point-to-point links.

1. Point-to-Point Links:

To connect the central node to each peripheral node, Point-to-point links are created. The data rate and delay are configured for the links.

1. Network Stack:

On all nodes, the internet stack is installed.

1. IP Addresses:

To the nodes, IP addresses are assigned connected by the point-to-point links.

1. Applications:

On one of the peripheral nodes, A UDP server is installed and a UDP client is installed on the central node to generate traffic and demonstrate communication.

1. Packet Capture:

To observe network traffic, packet capture is enabled for the point-to-point links.

1. Logging:

To provide detailed output during the simulation, logging is enabled for the UDP client and server applications.

Running the Simulation

Compile and run the simulation using the following commands:

./waf configure

./waf build

./waf –run point-to-multipoint-topology-example

Replace point-to-multipoint-topology-example with the actual name of your script file.

Overall, we had our implementation results on point-to-multipoint topology in ns3 by creating a network where a single central node is connected to multiple peripheral nodes. Also, we provide detailed explanation on Point-to-multipoint Topology.

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