How to Begin Implement Dijkstra’s Link State Routing in NS3

To start Dijkstra’s Link State Routing utilising NS3 that has requires designing a routing protocol which leverages Dijkstra’s algorithm for determining the shortest path in the network from each node to every other node. This routing mechanism is appropriate for networks in which all nodes sustain a global outlook of the topology like OSPF (Open Shortest Path First).

We can follow these steps on how to execute Dijkstra’s Link State Routing in NS3:

Steps to Begin Implement Dijikstra’s Link State Routing in NS3

Step 1: Understand Link State Routing with Dijkstra

1. Key Concepts:
   • Link State Advertisements (LSAs):
     • Nodes distribute its link state such as neighbors and link costs including all other nodes.
   • Topology Database:
     • Every single node builds a global outlook of the network leveraging inherited LSAs.
   • Shortest Path Calculation:
     • Find the shortest path to all other node using Dijkstra’s algorithm.
2. Steps in Link State Routing:
   • Determine neighbors and connection costs.
   • Overflow LSAs to distribute topology data.
   • Find shortest routes to utilize Dijkstra’s algorithm.

Step 2: Set Up NS3 Environment

1. Create a Protocol Directory:
   • Make a protocol directory in src/, for instance src/link-state-routing/.
2. Add Necessary Files:
   • link-state-routing-protocol.h: Header file for the routing protocol.
   • link-state-routing-protocol.cc: For the routing protocol, it contains execution file.
   • link-state-routing-helper.h and link-state-routing-helper.cc: Helper classes to add protocol to the simulations.
3. Update Build System:
   • Adjust the wscript in src/ with the new component.

Step 3: Design Link State Routing Protocol

Define the Protocol Class

Execute the routing protocol logic for prolonging the Ipv4RoutingProtocol class.

Header File (link-state-routing-protocol.h)

#include “ns3/ipv4-routing-protocol.h”

#include “ns3/socket.h”

#include “ns3/timer.h”

#include <map>

#include <set>

class LinkStateRoutingProtocol : public ns3::Ipv4RoutingProtocol {

public:

static ns3::TypeId GetTypeId (void);

LinkStateRoutingProtocol ();

virtual ~LinkStateRoutingProtocol ();

// Override Ipv4RoutingProtocol methods

virtual ns3::Ptr<ns3::Ipv4Route> RouteOutput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<ns3::NetDevice> oif,

ns3::Socket::SocketErrno &sockerr);

virtual bool RouteInput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<const ns3::NetDevice> idev,

ns3::UnicastForwardCallback ucb,

ns3::MulticastForwardCallback mcb,

ns3::LocalDeliverCallback lcb,

ns3::ErrorCallback ecb);

// Link State Routing Methods

void FloodLinkStateAdvertisement ();

void ProcessLinkStateAdvertisement (ns3::Ptr<const ns3::Packet> packet);

void ComputeShortestPaths ();

private:

struct LinkState {

ns3::Ipv4Address neighbor;

uint32_t cost;

};

struct NodeState {

ns3::Ipv4Address nodeAddress;

std::vector<LinkState> neighbors;

};

ns3::Ipv4Address m_selfAddress;

std::map<ns3::Ipv4Address, NodeState> m_topologyDatabase; // Global topology

std::map<ns3::Ipv4Address, ns3::Ipv4Address> m_routingTable; // Destination -> Next hop

ns3::Timer m_lsaTimer; // Periodic LSA flooding

};

Implement Core Functions

Flood Link State Advertisement

Overflow LSAs periodically to distribute the local link state.

void LinkStateRoutingProtocol::FloodLinkStateAdvertisement () {

// Create LSA packet

ns3::Ptr<ns3::Packet> packet = ns3::Create<ns3::Packet> ();

// Serialize local topology information into the packet

// …

// Broadcast LSA

m_socket->SendTo(packet, 0, ns3::InetSocketAddress(ns3::Ipv4Address::GetBroadcast(), 9999));

// Schedule next LSA flooding

m_lsaTimer.Schedule(ns3::Seconds(10.0));

}

Process Incoming LSAs

Modernize the topology database once inheriting the LSAs.

void LinkStateRoutingProtocol::ProcessLinkStateAdvertisement (ns3::Ptr<const ns3::Packet> packet) {

// Deserialize LSA packet

NodeState nodeState = …; // Extract node state information

// Update topology database

m_topologyDatabase[nodeState.nodeAddress] = nodeState;

// Recompute shortest paths

ComputeShortestPaths ();

}

Compute Shortest Paths Using Dijkstra’s Algorithm

Execute the Dijkstra’s algorithm for determining shortest paths from the node to every destination.

void LinkStateRoutingProtocol::ComputeShortestPaths () {

// Use Dijkstra’s algorithm

std::set<ns3::Ipv4Address> visited;

std::map<ns3::Ipv4Address, uint32_t> distances;

std::map<ns3::Ipv4Address, ns3::Ipv4Address> previous;

// Initialize distances

for (const auto &entry : m_topologyDatabase) {

distances[entry.first] = std::numeric_limits<uint32_t>::max();

}

distances[m_selfAddress] = 0;

// Dijkstra’s main loop

while (!visited.empty()) {

// Find the node with the smallest distance

ns3::Ipv4Address currentNode = …;

// Update distances for neighbors

for (const auto &neighbor : m_topologyDatabase[currentNode].neighbors) {

uint32_t newDistance = distances[currentNode] + neighbor.cost;

if (newDistance < distances[neighbor.neighbor]) {

distances[neighbor.neighbor] = newDistance;

previous[neighbor.neighbor] = currentNode;

}

}

visited.insert(currentNode);

}

// Build routing table

for (const auto &entry : previous) {

m_routingTable[entry.first] = entry.second;

}

}

Packet Forwarding

Execute the packet forwarding with the support of determined routing table.

ns3::Ptr<ns3::Ipv4Route> LinkStateRoutingProtocol::RouteOutput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<ns3::NetDevice> oif,

ns3::Socket::SocketErrno &sockerr) {

ns3::Ptr<ns3::Ipv4Route> route = ns3::Create<ns3::Ipv4Route> ();

if (m_routingTable.find(header.GetDestination()) != m_routingTable.end()) {

route->SetGateway(m_routingTable[header.GetDestination()]);

} else {

sockerr = ns3::Socket::ERROR_NOROUTETOHOST;

return nullptr;

}

return route;

}

Step 4: Write a Helper Class

Make a helper class to make easier incorporation within simulations.

#include “link-state-routing-protocol.h”

class LinkStateRoutingHelper {

public:

void Install (ns3::NodeContainer nodes) {

for (auto it = nodes.Begin(); it != nodes.End(); ++it) {

ns3::Ptr<LinkStateRoutingProtocol> protocol = ns3::CreateObject<LinkStateRoutingProtocol>();

(*it)->AggregateObject(protocol);

}

}

};

Step 5: Write a Simulation Script

Example Simulation Script

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “link-state-routing-helper.h”

using namespace ns3;

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

NodeContainer nodes;

nodes.Create (5);

InternetStackHelper stack;

stack.Install (nodes);

LinkStateRoutingHelper lsrHelper;

lsrHelper.Install (nodes);

// Configure links and addresses

PointToPointHelper p2p;

p2p.SetDeviceAttribute (“DataRate”, StringValue (“10Mbps”));

p2p.SetChannelAttribute (“Delay”, StringValue (“2ms”));

p2p.Install (nodes.Get (0), nodes.Get (1));

p2p.Install (nodes.Get (1), nodes.Get (2));

// Add additional links…

// Simulate traffic…

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

Step 6: Compile and Run

1. Build the Protocol:

./waf configure

./waf build

1. Run the Simulation:

./waf –run your-script

Step 7: Analyze and Extend

1. Tracing Tools:
   • Examine the packet flows with PcapHelper or AsciiTraceHelper.
2. Enhancements:
   • Integrate the support for mobility.
   • Enhance LSA flooding for minimizing overhead.

Detailed and sequential steps for implementing and examining the Dijkstra’s Link State Routing using NS3 have been offered. We’re ready to include more details and additional concepts, if necessary.