How to Begin Implement Distributed Routing in NS3

To implement Distributed Routing within NS3 focuses on designing a routing protocol in which nodes determine the routes independently with the support of local data and neighbor exchanges. Distributed routing protocols are generally leveraged within large-scale networks in which global data isn’t possible to handle.

Below is a detailed approach on how to begin executing the Distributed Routing in NS3:

Steps to Begin Implement Distributed Routing in NS3

Step 1: Understand Distributed Routing Basics

1. Key Concepts:
   • Nodes sustain the routing tables according to the local and neighbor data.
   • Interchange routing tables or updates periodically including the neighbors.
   • Routes are independently determined through every single node to utilize protocols such as:
     • Distance-Vector (e.g., RIP): Transmits according to the hop counts or costs.
     • Link-State (e.g., OSPF): Entire topology awareness by LSAs.
2. Characteristics of Distributed Routing:
   • If functions devoid of a central controller.
   • It is used for scalability and fault tolerance.
   • Efficiently manages the dynamic topology modifications.

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: Execute an example script:

./ns3 run examples/tutorial/first

Step 3: Plan the Distributed Routing Protocol Design

1. Core Components:
   • Routing Table: Sustains destination, next hop, and cost for every single node.
   • Periodic Updates: Periodically interchange the routing tables or incremental updates including neighbors.
   • Route Computation: According to the received data, modernize routing tables.
2. Workflow Example:
   • Every single node sets their routing table.
   • Nodes swap routing tables periodically by neighbors.
   • Depends on the neighbor data, routing tables are modernized.
   • Packets are sent rely on the routing table.

Step 4: Implement Distributed Routing

Step 4.1: Define the Protocol Class

Make a custom routing protocol class by means of prolonging the Ipv4RoutingProtocol:

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

#include “ns3/socket.h”

#include <map>

using namespace ns3;

class DistributedRouting : public Ipv4RoutingProtocol {

public:

static TypeId GetTypeId(void);

DistributedRouting();

virtual ~DistributedRouting();

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 NotifyInterfaceUp(uint32_t interface) override;

void NotifyInterfaceDown(uint32_t interface) override;

private:

void InitializeRoutingTable();

void SendRoutingUpdates();

void ReceiveRoutingUpdates(Ptr<Socket> socket);

void UpdateRoutingTable(Ipv4Address neighbor, const std::map<Ipv4Address, uint32_t> &neighborTable);

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

Ptr<Socket> m_socket;

};

Step 4.2: Implement Core Functions

• Initialize Routing Table: Inhabit the routing table using direct neighbors.

void DistributedRouting::InitializeRoutingTable() {

for (uint32_t i = 0; i < GetNode()->GetNDevices(); ++i) {

Ptr<NetDevice> device = GetNode()->GetDevice(i);

Ipv4Address address = GetNode()->GetObject<Ipv4>()->GetAddress(i, 0).GetLocal();

m_routingTable[address] = {address, 0}; // Cost to itself is 0

}

}

• Send Routing Updates: Transmit the routing table which renovates to neighbors.

void DistributedRouting::SendRoutingUpdates() {

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

for (const auto &entry : m_routingTable) {

// Serialize routing table entries into packet

}

for (uint32_t i = 0; i < GetNode()->GetNDevices(); ++i) {

Ptr<NetDevice> device = GetNode()->GetDevice(i);

m_socket->SendTo(packet, 0, InetSocketAddress(Ipv4Address(“255.255.255.255”), 520));

}

Simulator::Schedule(Seconds(10.0), &DistributedRouting::SendRoutingUpdates, this);

}

• Update Routing Table: Rely on inherited neighbor updates modernize the routing table.

void DistributedRouting::UpdateRoutingTable(Ipv4Address neighbor,

const std::map<Ipv4Address, uint32_t> &neighborTable) {

for (const auto &entry : neighborTable) {

Ipv4Address dest = entry.first;

uint32_t costToDest = entry.second;

uint32_t newCost = m_routingTable[neighbor].second + costToDest;

if (m_routingTable.find(dest) == m_routingTable.end() || newCost < m_routingTable[dest].second) {

m_routingTable[dest] = {neighbor, newCost};

}

}

}

• Handle Routing Input and Output:

Ptr<Ipv4Route> DistributedRouting::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); // Use NextHop from routing table

route->SetOutputDevice(oif);

}

return route;

}

bool DistributedRouting::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); // Deliver locally

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); // Use NextHop from routing table

ucb(route, packet, header);

return true;

}

return false;

}

Step 5: Register the Protocol with NS3

1. TypeId Registration:

TypeId DistributedRouting::GetTypeId(void) {

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

.SetParent<Ipv4RoutingProtocol>()

.SetGroupName(“Internet”)

.AddConstructor<DistributedRouting>();

return tid;

}

Step 6: Integrate into a Simulation

1. Simulation Script Example:

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

#include “ns3/distributed-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<DistributedRouting> distRouting = CreateObject<DistributedRouting>();

stack.SetRoutingHelper(distRouting);

stack.Install(nodes);

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 7: Test and Debug

1. Enable Logging:

export NS_LOG=”DistributedRouting=level_all|prefix_time”

./ns3 run my-simulation

1. Validate:
   • Confirm for routing table convergence time.
   • Observe the packet delivery and routing exactness.

Step 8: Optimize and Extend

1. Enhancements:
   • Execute the loop prevention approaches such as divided horizon.
   • Make use of dynamic parameters such as delay or bandwidth.
2. Performance Testing:
   • Experiment the performance at larger network topologies.
   • Examine scalability and convergence time.

With the help of this implementation procedure, we had delivered the valuable insights regarding how to implement and analyze the Distributed Routing in NS3 environment. We are equipped to present more detailed insights on this topic in upcoming manual.