How to Start Flow Based Routing Projects Using NS3

To start a Flow-Based Routing project using NS3, we follow this structured guide:

Steps to Start Flow Based Routing Projects in NS3

  1. Understand Flow-Based Routing
  • Flow-Based Routing:
    • Packets are routed according to the flows (group of packets with common attributes like source and destination IP/port) in this routing mechanism.
    • This routing is frequently utilized within Software-Defined Networking (SDN) in which flow rules are predefined or actively allocated by a centralized controller.
  • Applications:
    • Traffic Engineering.
    • Quality of Service (QoS).
    • Network Function Virtualization (NFV).
  1. Set Up NS3
  1. We should install NS3 on the system:

sudo apt update

sudo apt install g++ python3 git cmake

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

cd ns-3-dev

./waf configure

./waf build

  1. Verify installation:

./waf –run scratch/my-first

  1. Approach to Implement Flow-Based Routing
  1. Option 1: Make use of pre-existing NS3 modules such as static or dynamic routing and then alter the logic executing flow-based routing.
  2. Option 2: Alternatively, we execute a custom routing protocol by means of prolonging the Ipv4RoutingProtocol class.
  1. Basic Flow-Based Routing Simulation

Below is an instance of flow-based routing in which routes are described for certain flows (e.g., based on destination IP).

Code Example:

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

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

#include “ns3/ipv4-static-routing-helper.h”

using namespace ns3;

int main() {

// Create 4 nodes

NodeContainer nodes;

nodes.Create(4);

// Set up point-to-point links

PointToPointHelper pointToPoint;

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

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

NetDeviceContainer devices1 = pointToPoint.Install(nodes.Get(0), nodes.Get(1));

NetDeviceContainer devices2 = pointToPoint.Install(nodes.Get(1), nodes.Get(2));

NetDeviceContainer devices3 = pointToPoint.Install(nodes.Get(2), nodes.Get(3));

// Install Internet stack

InternetStackHelper stack;

stack.Install(nodes);

// Assign IP addresses

Ipv4AddressHelper address;

address.SetBase(“10.1.1.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces1 = address.Assign(devices1);

address.SetBase(“10.1.2.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces2 = address.Assign(devices2);

address.SetBase(“10.1.3.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces3 = address.Assign(devices3);

// Define flow-based routing

Ipv4StaticRoutingHelper staticRoutingHelper;

Ptr<Ipv4StaticRouting> staticRoutingNode0 = staticRoutingHelper.GetStaticRouting(nodes.Get(0)->GetObject<Ipv4>());

// Route flow to destination 10.1.3.2 via Node 1 and Node 2

staticRoutingNode0->AddHostRouteTo(Ipv4Address(“10.1.3.2”), Ipv4Address(“10.1.1.2”), 1);

// Run the simulation

Simulator::Stop(Seconds(10.0));

Simulator::Run();

Simulator::Destroy();

return 0;

}

  1. Custom Flow-Based Routing Implementation

To make a custom flow-based routing protocol, we will require prolonging the Ipv4RoutingProtocol class.

Steps to Implement:

  1. Define the Routing Protocol: We make a new class FlowBasedRoutingProtocol, which receives from Ipv4RoutingProtocol.

Skeleton:

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

#include <map>

namespace ns3 {

class FlowBasedRoutingProtocol : public Ipv4RoutingProtocol {

public:

static TypeId GetTypeId();

FlowBasedRoutingProtocol();

virtual ~FlowBasedRoutingProtocol();

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

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

void AddFlowRoute(uint32_t flowId, Ipv4Address nextHop, uint32_t interface);

private:

std::map<uint32_t, std::pair<Ipv4Address, uint32_t>> flowTable; // Flow ID -> (Next Hop, Interface)

};

} // namespace ns3

  1. Implement the Logic:
    • In the RouteOutput technique, match packets to flow rules within the flowTable.
    • If a flow rule occurs then consequently send packets.
    • Unless packet lost or utilize a default route.

Example Implementation:

#include “FlowBasedRoutingProtocol.h”

#include “ns3/log.h”

namespace ns3 {

NS_LOG_COMPONENT_DEFINE(“FlowBasedRoutingProtocol”);

FlowBasedRoutingProtocol::FlowBasedRoutingProtocol() {}

FlowBasedRoutingProtocol::~FlowBasedRoutingProtocol() {}

TypeId FlowBasedRoutingProtocol::GetTypeId() {

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

.SetParent<Ipv4RoutingProtocol>()

.SetGroupName(“Internet”)

.AddConstructor<FlowBasedRoutingProtocol>();

return tid;

}

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

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

uint32_t flowId = packet->GetUid(); // Example: Use packet UID as a flow identifier

if (flowTable.find(flowId) != flowTable.end()) {

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

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

route->SetGateway(flowTable[flowId].first); // Next hop

route->SetOutputDevice(oif);

return route;

}

NS_LOG_WARN(“No route found for flow”);

return nullptr; // Drop packet if no route

}

void FlowBasedRoutingProtocol::AddFlowRoute(uint32_t flowId, Ipv4Address nextHop, uint32_t interface) {

flowTable[flowId] = std::make_pair(nextHop, interface);

}

} // namespace ns3

This guide uncovered the step-by-step initiation and implementation process for Flow Based Routing Projects, which were successfully executed using NS3 tool. Upon your requests, we are equipped to extend this project in another manual.

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