How to Begin Implement Shortest Path Routing in NS3

To begin a Shortest Path Routing in NS3 has includes the build a custom routing protocol which calculate the shortest path among nodes according to their metric such as hop count, delay, or link cost. This can be accomplished through leveraging procedures such as Dijkstra’s Algorithm or Bellman-Ford Algorithm for measure the optimal paths.

Here’s a detailed guide to get started:

Steps to Begin Implement Shortest Path Routing in NS3

Step 1: Understand Shortest Path Routing Basics

1. Key Concepts:
   • Shortest Path: The path among the source and destination by least cost terms on express the metric for sample number of hops, link delay, and bandwidth.
   • Topology Awareness: The routing protocols are should recognize the network topology for estimate the paths.
2. Algorithm Choice:
   • Dijkstra’s Algorithm: Appropriate for link-state protocols in which the node has the complete network topology.
   • Bellman-Ford Algorithm: It operates well in distance-vector protocols in which nodes are distributing the partial knowledge by neighbor.
3. Routing Table:
   • Destination: It aims the node.
   • Next Hop: Intermediate the node for transmitting the packet.
   • Cost: The parameter metric has charge for the path.

Step 2: Set Up NS-3

1. Install NS-3:

git clone https://gitlab.com/nsnam/ns-3-dev.git

cd ns-3-dev

./ns3 configure –enable-examples –enable-tests

./ns3 build

1. Verify Installation: Run an example:

./ns3 run examples/tutorial/first

Step 3: Plan the Protocol Design

1. Components:
   • Topology Discovery: It collects the network topology information for instance neighbor discovery or link-state advertisement.
   • Routing Table Calculation: Utilized their Dijkstra’s procedures for calculate the shortest paths.
   • Packet Forwarding: Transmitting the packets according to their measured a routing table.
2. Workflow:
   • Gather the network topology information from neighbor or the network.
   • Estimate the shortest paths using the collected a network topology.
   • Bring up-to-date the routing table and transmit the packets accordingly.

Step 4: Implement Shortest Path Routing

Step 4.1: Define the Protocol Class

Encompass the Ipv4RoutingProtocol class for develop a custom routing protocol:

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

#include “ns3/node.h”

#include “ns3/socket.h”

#include <map>

using namespace ns3;

class ShortestPathRouting : public Ipv4RoutingProtocol {

public:

static TypeId GetTypeId(void);

ShortestPathRouting();

virtual ~ShortestPathRouting();

virtual Ptr<Ipv4Route> RouteOutput(Ptr<Packet> packet, const Ipv4Header &header,

Ptr<NetDevice> oif, Socket::SocketErrno &sockerr) override;

virtual bool RouteInput(Ptr<const Packet> packet, const Ipv4Header &header,

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) override;

virtual void NotifyInterfaceUp(uint32_t interface) override;

virtual void NotifyInterfaceDown(uint32_t interface) override;

void ComputeShortestPaths();

private:

void DiscoverTopology();

void SendTopologyUpdates();

void ReceiveTopologyUpdates(Ptr<Socket> socket);

std::map<Ipv4Address, std::pair<Ipv4Address, uint32_t>> m_routingTable; // Destination -> (NextHop, Cost)

Ptr<Socket> m_socket;

std::map<Ipv4Address, std::map<Ipv4Address, uint32_t>> m_topology; // Topology graph

};

Step 4.2: Implement Core Functions

• Topology Discovery: Determine the neighbors and bring together data for network topology.

void ShortestPathRouting::DiscoverTopology() {

// Broadcast a topology discovery message to neighbors

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

m_socket->SendTo(packet, 0, InetSocketAddress(Ipv4Address(“255.255.255.255”), 9999));

}

void ShortestPathRouting::ReceiveTopologyUpdates(Ptr<Socket> socket) {

Ptr<Packet> packet = socket->Recv();

// Parse and update the topology graph

}

• Shortest Path Calculation: Evaluate the Dijkstra’s procedures for estimate the shortest paths.

void ShortestPathRouting::ComputeShortestPaths() {

std::map<Ipv4Address, uint32_t> distance;

std::map<Ipv4Address, Ipv4Address> previous;

// Initialize distances

for (auto &node : m_topology) {

distance[node.first] = UINT32_MAX;

}

distance[GetNode()->GetObject<Ipv4>()->GetAddress(1, 0).GetLocal()] = 0;

// Dijkstra’s algorithm

while (!distance.empty()) {

auto it = std::min_element(distance.begin(), distance.end(),

[](const auto &a, const auto &b) { return a.second < b.second; });

Ipv4Address current = it->first;

uint32_t currentDist = it->second;

distance.erase(it);

for (auto &neighbor : m_topology[current]) {

uint32_t newDist = currentDist + neighbor.second;

if (newDist < distance[neighbor.first]) {

distance[neighbor.first] = newDist;

previous[neighbor.first] = current;

}

}

}

// Update routing table

for (auto &node : previous) {

m_routingTable[node.first] = {node.second, distance[node.first]};

}

}

• Packet Forwarding: Forward packets according to the computed routing table.

Ptr<Ipv4Route> ShortestPathRouting::RouteOutput(Ptr<Packet> packet, const Ipv4Header &header,

Ptr<NetDevice> oif, Socket::SocketErrno &sockerr) {

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

auto it = m_routingTable.find(header.GetDestination());

if (it != m_routingTable.end()) {

route->SetDestination(header.GetDestination());

route->SetGateway(it->second.first); // Next hop

route->SetOutputDevice(oif);

}

return route;

}

bool ShortestPathRouting::RouteInput(Ptr<const Packet> packet, const Ipv4Header &header,

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) {

if (header.GetDestination() == GetNode()->GetObject<Ipv4>()->GetAddress(1, 0).GetLocal()) {

lcb(packet, header, idev);

return true;

}

auto it = m_routingTable.find(header.GetDestination());

if (it != m_routingTable.end()) {

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

route->SetDestination(header.GetDestination());

route->SetGateway(it->second.first); // Next hop

ucb(route, packet, header);

return true;

}

return false;

}

Step 5: Integrate the Protocol

Step 5.1: Register the Protocol

Store the protocol by NS3’s TypeId system:

TypeId ShortestPathRouting::GetTypeId(void) {

static TypeId tid = TypeId(“ns3::ShortestPathRouting”)

.SetParent<Ipv4RoutingProtocol>()

.SetGroupName(“Internet”)

.AddConstructor<ShortestPathRouting>();

return tid;

}

Step 5.2: Add to Simulation

Incorporate the protocol in a replication script:

#include “ns3/internet-stack-helper.h”

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

NodeContainer nodes;

nodes.Create(4);

PointToPointHelper p2p;

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

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

NetDeviceContainer devices = p2p.Install(nodes.Get(0), nodes.Get(1));

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

devices.Add(p2p.Install(nodes.Get(2), nodes.Get(3)));

InternetStackHelper stack;

Ptr<ShortestPathRouting> sprRouting = CreateObject<ShortestPathRouting>();

stack.SetRoutingHelper(sprRouting);

stack.Install(nodes);

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 6: Test and Debug

1. Enable Logging: Use logging system NS-3’s:

export NS_LOG=”ShortestPathRouting=level_all|prefix_time”

./ns3 run my-simulation

1. Validate Results:
   • Validate the routing table correctness.
   • FlowMonitor for utilized their examine path selection.

Step 7: Extend and Optimize

1. Enhancements:
   • Enhance the connection cost parameter metrics such as bandwidth, delay, or consistency.
   • Evaluate the QoS-aware routing.
2. Performance Testing:
   • Investigate by larger topologies.
   • Enhance the dynamic topologies by repeated modification.

These project ideas focus on testing Shortest Path Routing using NS3 to understand their performance in different conditions. Any queries related to this project will be clarified in a different manual.