How to Begin Implement a Layer 3 Route Protocol in NS3

To start executing a Layer 3 (L3) routing protocol utilising NS3 consist of either leveraging existing routing protocols or making a custom protocol, which functions on IP layer (Layer 3) for handling the routing decisions and packet forwarding. While NS3 environment offers numerous pre-implemented routing protocols such as AODV, OLSR, RIP, and DSR, for a custom Layer 3 protocol, we can prolong the Ipv4RoutingProtocol interface of NS3.

Now we are going to the brief procedure to execute a Layer 3 routing protocol using NS3:

Steps to Begin Implement a Layer 3 Route Protocol in NS3

1. Set Up ns3 Environment

1. Install ns3:
   • We should download and set up NS3 on the computer.
   • Make sure that installation by executing a sample instance script as ./waf –run hello-simulator.
2. Include Required Modules:
   • Make certain necessary components such as internet, ipv4, and applications are allowed.

2. Understand Layer 3 Protocol Requirements

1. Routing Decisions:
   • Compute how packets will be transmitted using shortest path, link-state, or distance-vector routing.
   • Focus on how routes are launched and sustained by leveraging static, dynamic, or hybrid.
2. Packet Management:
   • It manages the incoming and outgoing packets on the IP layer.
   • Execute routing table maintenance.
3. Protocol Messages:
   • Describe the custom protocol messages for route discovery and updates as needed.

3. Create a Custom Layer 3 Routing Protocol
4. Define the Routing Protocol Class

Make a new class, which receives from Ipv4RoutingProtocol:

class CustomRoutingProtocol : public Ipv4RoutingProtocol {

public:

static TypeId GetTypeId();

CustomRoutingProtocol();

virtual ~CustomRoutingProtocol();

// Override required methods

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

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

bool RouteInput(Ptr<const Packet> p, 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;

void NotifyAddAddress(uint32_t interface, Ipv4InterfaceAddress address) override;

void NotifyRemoveAddress(uint32_t interface, Ipv4InterfaceAddress address) override;

void SetIpv4(Ptr<Ipv4> ipv4) override;

private:

Ptr<Ipv4> m_ipv4; // Pointer to the Ipv4 instance

RoutingTable m_routingTable; // Custom routing table

};

1. Implement Core Methods

1. Route Output:
   • Manage the packets to be transmitted by the node.

Ptr<Ipv4Route> CustomRoutingProtocol::RouteOutput(

Ptr<Packet> p, const Ipv4Header &header,

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

// Implement logic to determine the outgoing route

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

// Populate route fields (e.g., destination, source, next hop, etc.)

return route;

}

1. Route Input:
   • Manage incoming packets and choose whether it locally transmitted or distributed.

bool CustomRoutingProtocol::RouteInput(

Ptr<const Packet> p, const Ipv4Header &header,

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) {

// Implement forwarding logic or local delivery

return true;

}

1. Routing Table:
   • Execute a data structure for sustaining routing data.

class RoutingTable {

public:

void AddRoute(Ipv4Address dest, Ipv4Address nextHop, uint32_t interface);

void RemoveRoute(Ipv4Address dest);

Ptr<Ipv4Route> Lookup(Ipv4Address dest);

private:

std::map<Ipv4Address, Ptr<Ipv4Route>> m_routes;

};

1. Protocol Messages

• Describe the custom headers or messages for route discovery or updates, as required.

class CustomRoutingHeader : public Header {

public:

void Serialize(Buffer::Iterator start) const override;

uint32_t Deserialize(Buffer::Iterator start) override;

void Print(std::ostream &os) const override;

};

4. Set Up Network Topology

1. Create Nodes:
   • Make nodes within the network.

NodeContainer nodes;

nodes.Create(10); // Create 10 nodes

1. Configure Links:
   • Apply PointToPointHelper or CsmaHelper to make connections.

PointToPointHelper p2p;

p2p.SetDeviceAttribute(“DataRate”, StringValue(“1Gbps”));

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

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

1. Install the Network Stack:
   • Integrate the network stack and traditional routing protocol.

InternetStackHelper internet;

Ptr<CustomRoutingProtocol> customRouting = CreateObject<CustomRoutingProtocol>();

internet.SetRoutingHelper(customRouting);

internet.Install(nodes);

1. Assign IP Addresses:
   • Allocate inimitable IP addresses to the nodes.

Ipv4AddressHelper ipv4;

ipv4.SetBase(“10.1.1.0”, “255.255.255.0”);

ipv4.Assign(devices);

5. Simulate Traffic

1. Install Applications:
   • Mimic traffic to leverage the applications such as UdpEchoClient and UdpEchoServer.

UdpEchoServerHelper echoServer(9);

ApplicationContainer serverApps = echoServer.Install(nodes.Get(9)); // Server at node 9

serverApps.Start(Seconds(1.0));

serverApps.Stop(Seconds(10.0));

UdpEchoClientHelper echoClient(Ipv4Address(“10.1.1.10”), 9);

echoClient.SetAttribute(“MaxPackets”, UintegerValue(20));

echoClient.SetAttribute(“Interval”, TimeValue(Seconds(1.0)));

echoClient.SetAttribute(“PacketSize”, UintegerValue(1024));

ApplicationContainer clientApps = echoClient.Install(nodes.Get(0)); // Client at node 0

clientApps.Start(Seconds(2.0));

clientApps.Stop(Seconds(10.0));

1. Monitor Traffic:
   • Observe the received packets in PacketSink.

6. Enable Tracing and Logging

1. PCAP Tracing:
   • Seize packets tracing for analysis.

p2p.EnablePcapAll(“layer3-routing”);

1. ASCII Logging:
   • Record all routing events using ASCII.

AsciiTraceHelper ascii;

p2p.EnableAsciiAll(ascii.CreateFileStream(“layer3-routing.tr”));

1. FlowMonitor:
   • Estimate the traffic performance parameters such as delay, throughput, and packet delivery ratio using FlowMonitor.

FlowMonitorHelper flowmon;

Ptr<FlowMonitor> monitor = flowmon.InstallAll();

7. Run the Simulation

1. Start the Simulator:

Simulator::Run();

Simulator::Destroy();

1. Export Results:
   • For in-depth analysis, we can store FlowMonitor outcomes.

monitor->SerializeToXmlFile(“layer3-routing-results.xml”, true, true);

8. Analyze and Visualize Results

1. Traffic Analysis:
   • Measure the performance of protocol with the help of PCAP files or FlowMonitor data.
2. NetAnim Visualization:
   • Envision routing behavior and packet flow by applying NetAnim tools.

AnimationInterface anim(“layer3-routing.xml”);

9. Extend and Optimize

1. Dynamic Topology:
   • Replicate the mobility to experiment performance of protocol under dynamic topology scenarios.
2. QoS Routing:
   • Integrate QoS routing indicators such as bandwidth or latency for enhancing the routing decisions.
3. Scalability:
   • Maximize the network size for computing scalability.

We used NS3 environment to perform detailed implementation process, which goal is to manage the routing decisions and packet forwarding on Layer 3 Projects that were executed and analysed. Should it be needed, we are ready to provide deeper insights and relevant information.