How to Begin Implement Flow Based Routing in NS3

To implement Flow-based routing utilizing NS3 that needs to make a custom routing protocol in which the sending decision is according to the certain flow identifiers for packets like source/destination IP addresses, ports, protocol, or other criteria. This kind of routing is typically leveraged within Software-Defined Networking (SDN), Quality of Service (QoS), and traffic engineering scenarios.

Below is a detailed implementation process to get started:

Steps to Begin Implement Flow Based Routing in NS3

Step 1: Understand Flow-Based Routing

1. Key Concepts:
   • Flow Identification: A flow is normally described by a 5-tuple like:
     • Source IP, Destination IP, Source Port, Destination Port, Protocol.
   • Flow Table: A table saves routing decisions (next hop) for certain flows.
   • Flow Management: Packets are matched versus the flow table for computing its forwarding routes.
2. Characteristics:
   • It offers fine-grained routing decisions.
   • It can be prolonged for QoS-aware routing or SDN-style mechanisms.

Step 2: Set Up NS3

1. Install NS3:

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: Confirm set up by executing a basic instance script:

./ns3 run examples/tutorial/first

Step 3: Plan the Flow-Based Routing Protocol

1. Core Components:
   • Flow Table: Connects flow identifiers to routing decisions.
   • Flow Matching: Equal incoming packets versus flow accesses.
   • Flow Installation: Dynamically integrate or modernize the flow rules for example according to the network strategies.
2. Implementation Workflow:
   • Describe the flow table structure.
   • Equal incoming packets to flow table accesses.
   • Depends on the similar flow, to send packets.

Step 4: Implement Flow-Based Routing

Step 4.1: Define the Protocol Class

Execute the custom protocol for prolonging the Ipv4RoutingProtocol class:

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

#include “ns3/socket.h”

#include <map>

#include <tuple>

using namespace ns3;

class FlowBasedRouting : public Ipv4RoutingProtocol {

public:

static TypeId GetTypeId(void);

FlowBasedRouting();

virtual ~FlowBasedRouting();

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;

void AddFlow(Ipv4Address src, Ipv4Address dst, uint16_t srcPort, uint16_t dstPort, uint8_t protocol, Ipv4Address nextHop);

private:

using FlowKey = std::tuple<Ipv4Address, Ipv4Address, uint16_t, uint16_t, uint8_t>; // Flow identifier

std::map<FlowKey, Ipv4Address> m_flowTable; // Maps flow key to next hop

};

Step 4.2: Implement Core Functions

• Add a Flow: Integrate entries to the flow table.

void FlowBasedRouting::AddFlow(Ipv4Address src, Ipv4Address dst, uint16_t srcPort, uint16_t dstPort, uint8_t protocol, Ipv4Address nextHop) {

FlowKey key = std::make_tuple(src, dst, srcPort, dstPort, protocol);

m_flowTable[key] = nextHop;

}

• Match Packets to Flows: Equal received packets versus the flow table.

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

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

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

for (const auto &entry : m_flowTable) {

FlowKey key = entry.first;

if (std::get<0>(key) == header.GetSource() &&

std::get<1>(key) == header.GetDestination()) {

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

route->SetGateway(entry.second); // Use next hop from flow table

route->SetOutputDevice(oif);

return route;

}

}

sockerr = Socket::ERROR_NOROUTETOHOST;

return nullptr;

}

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

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) {

for (const auto &entry : m_flowTable) {

FlowKey key = entry.first;

if (std::get<0>(key) == header.GetSource() &&

std::get<1>(key) == header.GetDestination()) {

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

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

route->SetGateway(entry.second); // Use next hop from flow table

ucb(route, packet, header);

return true;

}

}

return false; // No matching flow found

}

Step 5: Register the Protocol with NS3

Record the protocol using TypeId system for incorporating it to the NS3:

TypeId FlowBasedRouting::GetTypeId(void) {

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

.SetParent<Ipv4RoutingProtocol>()

.SetGroupName(“Internet”)

.AddConstructor<FlowBasedRouting>();

return tid;

}

Step 6: Integrate into a Simulation

1. Simulation Script Example:

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

#include “ns3/flow-based-routing.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<FlowBasedRouting> flowRouting = CreateObject<FlowBasedRouting>();

flowRouting->AddFlow(Ipv4Address(“10.1.1.1”), Ipv4Address(“10.1.1.2”), 1000, 2000, 6, Ipv4Address(“10.1.1.2”)); // Example flow

stack.SetRoutingHelper(flowRouting);

stack.Install(nodes);

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 7: Test and Debug

1. Enable Logging: Make use of NS3’s logging system to debug:

export NS_LOG=”FlowBasedRouting=level_all|prefix_time”

./ns3 run my-simulation

1. Verify Results:
   • Confirm flow-based decisions.
   • Observe the flow table matching and packet distribution.

Step 8: Extend and Optimize

1. Enhancements:
   • Integrate the dynamic flow installation and elimination.
   • It contains QoS parameters within flow rules such as bandwidth or latency.
2. Performance Testing:
   • Experiment the performance in large-scale networks.
   • Examine flow table scalability and better performance.

In this guide, you can obtain the knowledge on how to start and implement the Flow Based Routing using NS3 simulation tool through the comprehensive procedure with relevant sample snippets. We are ready to give further detailed insights about this topic in another manual.