How to Implement DODAG Fault Tolerance in ns3

To implement DODAG (Destination-Oriented Directed Acyclic Graph) fault tolerance in ns3, we have to build a network simulation that should be able to find faults in RPL (Routing Protocol for Low-Power and Lossy Networks) environment. RPL is designed for IPv6-based low-power and lossy networks, and DODAG is a core part of its routing structure.

Here, we provide a step-by-step implementation to achieve this:

Step-by-Step Implementation:

Step 1: Setup ns3 Environment

Make certain that ns3 is installed on your system.

Step 2: Include Necessary Modules

In the script, we have to  include the necessary ns3 modules.

#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”

#include “ns3/ipv6-static-routing-helper.h”

#include “ns3/ipv6-routing-helper.h”

#include “ns3/rpl-helper.h”

#include “ns3/mobility-module.h”

Step 3: Create the Simulation Script

1. Setup Nodes and Network:

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“DODAGFaultTolerance”);

void SimulateFault (Ptr<Node> node)

{

NS_LOG_UNCOND (“Simulating fault on node ” << node->GetId () << ” at ” << Simulator::Now ().GetSeconds () << ” seconds”);

Ptr<Ipv6> ipv6 = node->GetObject<Ipv6> ();

// Simulate fault by disabling the node’s interface

ipv6->SetDown (1);

}

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

{

CommandLine cmd;

cmd.Parse (argc, argv);

// Create nodes

NodeContainer nodes;

nodes.Create (10);

// Set up point-to-point links

PointToPointHelper pointToPoint;

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

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

NetDeviceContainer devices;

for (uint32_t i = 0; i < nodes.GetN () – 1; ++i)

{

devices.Add (pointToPoint.Install (nodes.Get (i), nodes.Get (i + 1)));

}

// Install Internet stack

InternetStackHelper internetv6;

internetv6.Install (nodes);

// Assign IPv6 addresses

Ipv6AddressHelper ipv6;

ipv6.SetBase (Ipv6Address (“2001:db8::”), Ipv6Prefix (64));

Ipv6InterfaceContainer interfaces = ipv6.Assign (devices);

// Install RPL

RplHelper rplHelper;

rplHelper.Install (nodes);

// Set up mobility model

MobilityHelper mobility;

mobility.SetMobilityModel (“ns3::ConstantPositionMobilityModel”);

mobility.Install (nodes);

// Set up applications

uint16_t port = 9;  // Discard port (RFC 863)

OnOffHelper onoff (“ns3::UdpSocketFactory”, Address (Inet6SocketAddress (interfaces.GetAddress (9, 1), port)));

onoff.SetConstantRate (DataRate (“1Mbps”));

ApplicationContainer apps = onoff.Install (nodes.Get (0));

apps.Start (Seconds (1.0));

apps.Stop (Seconds (20.0));

PacketSinkHelper sink (“ns3::UdpSocketFactory”, Address (Inet6SocketAddress (Ipv6Address::GetAny (), port)));

apps = sink.Install (nodes.Get (9));

apps.Start (Seconds (1.0));

apps.Stop (Seconds (20.0));

Step 4: Run the Simulation

Now we have to compile and run your simulation script:

./waf configure

./waf build

./waf –run DODAGFaultTolerance

Explanation

• Node Creation: Create a node that represents various devices in the network.
• Point-to-Point Links: Configure point-to-point links between nodes.
• Internet Stack: Install the Internet stack on all nodes with IPv6 support.
• IPv6 Configuration: Assign IPv6 addresses to the nodes.
• RPL Installation: Install RPL on the nodes to create a DODAG.
• Mobility: Set constant positions for nodes.
• Applications: Use OnOffApplication and PacketSink to simulate traffic between nodes.
• Fault Simulation: while the simulation, disable the node’s interface by simulating a fault.

Advanced Fault Tolerance Techniques

1. Redundancy:

If the node failures, it should be able to find the alternative paths that is available in DODAG by executing redundancy and adding various paths into it.

void AddRedundantPaths (Ptr<Node> node, Ipv6InterfaceContainer &interfaces)

{

// Add additional paths between nodes for redundancy

pointToPoint.Install (node, nodes.Get (4));

pointToPoint.Install (node, nodes.Get (5));

ipv6.Assign (devices);

}

// In main function, call AddRedundantPaths

AddRedundantPaths (nodes.Get (2), interfaces);

Dynamic Reconfiguration:

Based on the node failures, it has to detect and reconfigure the nodes by implementing dynamic reconfiguration.

void ReconfigureNetwork (Ptr<Node> node)

{

NS_LOG_UNCOND (“Reconfiguring network at ” << Simulator::Now ().GetSeconds () << ” seconds”);

// Implement logic to reconfigure network, e.g., updating routes

}

// Schedule reconfiguration

Simulator::Schedule (Seconds (6.0), &ReconfigureNetwork, nodes.Get (4));

Monitoring and Alerts:

To discover the failures and notify by generating the alerts, we have to execute monitoring.

void MonitorNetwork (Ptr<Node> node)

{

// Implement monitoring logic to detect failures

NS_LOG_UNCOND (“Monitoring network at ” << Simulator::Now ().GetSeconds () << ” seconds”);

}

// Schedule monitoring

Simulator::Schedule (Seconds (1.0), &MonitorNetwork, nodes.Get (0));

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