How to Begin Implement BGP routing in NS3

To begin a BGP (Border Gateway Protocol) in NS-3 tool has built a routing protocol which simulates the BGP’s behavior, like as route commercial, choose, and manage the path vector. Although NS-3 does not have the built-in BGP module, we can execute the unique using his extensible for routing framework.

Here’s a guide to help you begin implementing BGP Routing in NS-3:

Steps to Begin Implement BGR routing in NS3

Step 1: Understand BGP Basics

1. Key Concepts:
   • Autonomous Systems (AS): The network has below a single administrative domain.
   • Path Vector Protocol: Every BGP route has commercial it contains the full path for the destination.
   • Route Selection: BGP chooses improve the route according to their policy and path characteristics.
   • Message Types:
     • OPEN: Launch the connection among BGP peers.
     • UPDATE: Advertise or withdraw routes.
     • KEEPALIVE: It manages the connection.
     • NOTIFICATION: Specify the errors.
2. Features to Implement:
   • Determine the Peer.
   • Selection and Route advertisement.
   • Path vectors using the loop prevention.

Step 2: Set Up NS-3 Environment

1. Create a Protocol Directory:
   • Generate a directory below src/, e.g., src/bgp-routing/.
2. Add Required Files:
   • bgp-routing-protocol.h: Header file for the BGP protocol.
   • bgp-routing-protocol.cc: Execute the file.
   • bgp-routing-helper.h and bgp-routing-helper.cc: Replicate for helper classes.
3. Update Build System:
   • Alter the wscript in src/ has involves the BGP component.

Step 3: Design BGP Protocol

Define the Protocol Class

Encompass the Ipv4RoutingProtocol for execute the BGP logic.

Header File (bgp-routing-protocol.h)

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

#include “ns3/socket.h”

#include “ns3/timer.h”

#include <map>

#include <vector>

class BgpRoutingProtocol : public ns3::Ipv4RoutingProtocol {

public:

static ns3::TypeId GetTypeId (void);

BgpRoutingProtocol ();

virtual ~BgpRoutingProtocol ();

// Override Ipv4RoutingProtocol methods

virtual ns3::Ptr<ns3::Ipv4Route> RouteOutput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<ns3::NetDevice> oif,

ns3::Socket::SocketErrno &sockerr);

virtual bool RouteInput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<const ns3::NetDevice> idev,

ns3::UnicastForwardCallback ucb,

ns3::MulticastForwardCallback mcb,

ns3::LocalDeliverCallback lcb,

ns3::ErrorCallback ecb);

void EstablishPeer (ns3::Ipv4Address peer);

void SendUpdate (ns3::Ipv4Address destination, std::vector<ns3::Ipv4Address> path);

void HandleUpdate (ns3::Ptr<const ns3::Packet> packet);

private:

struct BgpRoute {

std::vector<ns3::Ipv4Address> path;

ns3::Ipv4Address nextHop;

};

ns3::Ipv4Address m_selfAddress;

std::map<ns3::Ipv4Address, BgpRoute> m_routingTable; // Destination -> Route

std::vector<ns3::Ipv4Address> m_peers;               // List of BGP peers

};

Implement Core Functions

Peer Establishment

Introduce the connections by BGP peers using the OPEN message.

void BgpRoutingProtocol::EstablishPeer (ns3::Ipv4Address peer) {

m_peers.push_back(peer);

// Send OPEN message to the peer

ns3::Ptr<ns3::Packet> openPacket = ns3::Create<ns3::Packet> ();

// Serialize OPEN message

// …

m_socket->SendTo(openPacket, 0, ns3::InetSocketAddress(peer, 179));

}

Route Advertisement

Routes for commercial to peer using the UPDATE communication.

void BgpRoutingProtocol::SendUpdate (ns3::Ipv4Address destination, std::vector<ns3::Ipv4Address> path) {

for (auto peer : m_peers) {

ns3::Ptr<ns3::Packet> updatePacket = ns3::Create<ns3::Packet> ();

// Serialize UPDATE message with destination and path

// …

m_socket->SendTo(updatePacket, 0, ns3::InetSocketAddress(peer, 179));

}

}

Handle Route Updates

Develop the incoming UPDATE messages and bring up-to-date the routing table.

void BgpRoutingProtocol::HandleUpdate (ns3::Ptr<const ns3::Packet> packet) {

// Deserialize UPDATE message

ns3::Ipv4Address destination = …; // Extract destination

std::vector<ns3::Ipv4Address> path = …; // Extract path

// Check for loops

if (std::find(path.begin(), path.end(), m_selfAddress) != path.end()) {

return; // Loop detected, ignore update

}

// Update routing table

m_routingTable[destination] = {path, packet->GetSource()};

// Propagate the update to peers

path.push_back(m_selfAddress);

SendUpdate(destination, path);

}

Packet Forwarding

Use the forward packets for BGP routing table.

ns3::Ptr<ns3::Ipv4Route> BgpRoutingProtocol::RouteOutput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<ns3::NetDevice> oif,

ns3::Socket::SocketErrno &sockerr) {

ns3::Ptr<ns3::Ipv4Route> route = ns3::Create<ns3::Ipv4Route> ();

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

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

route->SetGateway(it->second.nextHop);

route->SetOutputDevice(oif);

return route;

} else {

sockerr = ns3::Socket::ERROR_NOROUTETOHOST;

return nullptr;

}

}

Step 4: Write a Helper Class

Enable the incorporate of BGP in replication scripts.

#include “bgp-routing-protocol.h”

class BgpRoutingHelper {

public:

void Install (ns3::NodeContainer nodes) {

for (auto it = nodes.Begin(); it != nodes.End(); ++it) {

ns3::Ptr<BgpRoutingProtocol> protocol = ns3::CreateObject<BgpRoutingProtocol>();

(*it)->AggregateObject(protocol);

}

}

};

Step 5: Write a Simulation Script

Example Simulation Script

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “bgp-routing-helper.h”

using namespace ns3;

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

NodeContainer nodes;

nodes.Create (4);

InternetStackHelper stack;

stack.Install (nodes);

BgpRoutingHelper bgpHelper;

bgpHelper.Install (nodes);

PointToPointHelper p2p;

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

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

p2p.Install (nodes.Get (0), nodes.Get (1));

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

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

Ipv4AddressHelper ipv4;

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

ipv4.Assign (p2p.GetNetDeviceContainer());

// Establish BGP peers

ns3::Ptr<BgpRoutingProtocol> bgp0 = nodes.Get(0)->GetObject<BgpRoutingProtocol>();

ns3::Ptr<BgpRoutingProtocol> bgp1 = nodes.Get(1)->GetObject<BgpRoutingProtocol>();

bgp0->EstablishPeer(Ipv4Address(“10.1.1.2”));

bgp1->EstablishPeer(Ipv4Address(“10.1.1.1”));

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

Step 6: Compile and Run

1. Build the Protocol:

./waf configure

./waf build

1. Run the Simulation:

./waf –run your-script

Step 7: Analyze and Extend

1. Tracing:
   • AsciiTraceHelper or PcapHelper used to seizure the congestion study.
2. Enhancements:
   • Encourage for improve the route policies and filtering.
   • Execute the features such as AS-PATH, NEXT-HOP, and LOCAL-PREF.

With the help of this procedure you can obtain the knowledge and can be able to simulate the Border Gateway Protocol projects in ns3 tool. We will issue an additional document for queries related to this project.