How to Implement Ring Topology in ns3

To implement a ring topology in ns3, we need to create a network where each node is connected to two other nodes, forming a closed loop. Here is an interesting guide to set up a ring topology in ns3.

Steps to implement ring topology

1. Set Up ns3:
   • Make sure that ns3 is installed in the computer. If not, install it.
2. Create the Nodes:
   • To represent devices in the ring network, create a set of nodes.
3. Set Up the Point-to-Point Channels:
   • To connect each node to its two neighbours, forming a ring, 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 ring 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 (“RingTopologyExample”);

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

{

CommandLine cmd;

cmd.Parse (argc, argv);

// Create nodes

NodeContainer nodes;

nodes.Create (5); // Create 5 nodes for the ring

// Create point-to-point links to form a ring

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute (“DataRate”, StringValue (“100Mbps”));

pointToPoint.SetChannelAttribute (“Delay”, TimeValue (NanoSeconds (6560)));

NetDeviceContainer devices;

InternetStackHelper stack;

stack.Install (nodes);

Ipv4AddressHelper address;

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

{

NetDeviceContainer link;

if (i == nodes.GetN () – 1)

{

// Connect the last node to the first node to complete the ring

link = pointToPoint.Install (NodeContainer (nodes.Get (i), nodes.Get (0)));

}

else

{

// Connect the current node to the next node

link = pointToPoint.Install (NodeContainer (nodes.Get (i), nodes.Get (i + 1)));

}

devices.Add (link);

std::ostringstream subnet;

subnet << “10.1.” << i + 1 << “.0”;

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

address.Assign (link);

}

// Enable routing

Ipv4GlobalRoutingHelper::PopulateRoutingTables ();

// Create a UDP server on node 1

UdpServerHelper udpServer (9);

ApplicationContainer serverApp = udpServer.Install (nodes.Get (1));

serverApp.Start (Seconds (1.0));

serverApp.Stop (Seconds (10.0));

// Create a UDP client on node 0

UdpClientHelper udpClient (Ipv4Address (“10.1.2.1”), 9); // Assuming node 1’s IP is 10.1.2.1

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

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

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

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

clientApp.Start (Seconds (2.0));

clientApp.Stop (Seconds (10.0));

// Enable packet capture

pointToPoint.EnablePcapAll (“ring-topology”);

// Enable logging

LogComponentEnable (“UdpClient”, LOG_LEVEL_INFO);

LogComponentEnable (“UdpServer”, LOG_LEVEL_INFO);

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

Explanation

1. Setup:

Created five nodes connected by point-to-point links.

1. Point-to-Point Links:

To connect each node to its two neighbours, forming a ring, 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 node (node 1), A UDP server is installed and a UDP client is installed on another node (node 0) 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 ring-topology-example

Replace ring-topology-example with the actual name of your script file.

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