How to Implement Border Gateway Protocol in NS2

To implement the Border Gateway Protocol (BGP) using NS2 is a difficult task since NS2 is mainly created for mimicking small-scale networks and MANETs. It does not natively assist BGP that normally used in large-scale Internet routing. This protocol is an inter-domain routing protocol used to exchange routing information among the autonomous systems (ASes). But, we can expand NS2 by executing BGP functionality. Given below is a high-level process on how we may approach this:

Step-by-Step Implementation:

Step 1: Understand BGP Protocol

BGP is a path-vector protocol that maintains paths to various networks and creates a routing decisions according to the path attributes such as path length, policy-based routing, and prefix advertisement.

Step 2: Set Up NS2

Make sure NS2 is installed on the system. Check the installation by running a simple simulation. If we want a latest simulator with better BGP support then we deliberate using the simulation tool NS3 or another network simulator such as Quagga which an actual BGP execution that can be used in network simulations.

Step 3: Create the BGP Agent Class (C++)

We want to make a new C++ class in NS2 that executes BGP routing logic. This agent class should manage the following:

  • BGP Sessions: Determine BGP peering sessions with other BGP routers.
  • Route Advertisement: Promote prefixes to peers.
  • Route Selection: Choose the best route according to the BGP attributes.
  • Route Maintenance: Manage updates, withdrawals, and policy-based routing decisions.

The following is a basic structure:

#include <agent.h>

#include <packet.h>

#include <trace.h>

#include <address.h>

#include <map>

#include <vector>

class BGPAgent : public Agent {

public:

BGPAgent();

void recv(Packet* p, Handler* h);

void establishBGPSession(int peer);

void advertiseRoute(int prefix, int nextHop);

void selectBestRoute(int prefix);

void handleUpdate(Packet* p);

void withdrawRoute(int prefix);

protected:

std::map<int, int> routingTable_; // Prefix -> Next Hop

std::map<int, std::vector<int>> bgpTable_; // Prefix -> List of AS paths

std::vector<int> peers_; // List of BGP peers

};

// Constructor

BGPAgent::BGPAgent() : Agent(PT_TCP) {

// Initialization code here

}

// Packet reception

void BGPAgent::recv(Packet* p, Handler* h) {

// Handle BGP messages like UPDATE, WITHDRAW, etc.

handleUpdate(p);

}

// Establish a BGP session with a peer

void BGPAgent::establishBGPSession(int peer) {

// Implement session establishment logic (TCP handshake, etc.)

peers_.push_back(peer);

}

// Advertise a route to peers

void BGPAgent::advertiseRoute(int prefix, int nextHop) {

// Send UPDATE message to all peers

for (int peer : peers_) {

// Code to send the route advertisement

}

}

// Select the best route based on BGP attributes

void BGPAgent::selectBestRoute(int prefix) {

// Implement route selection logic based on AS path, etc.

}

// Handle route updates from peers

void BGPAgent::handleUpdate(Packet* p) {

// Process the UPDATE message, modify routing table accordingly

}

// Withdraw a route from peers

void BGPAgent::withdrawRoute(int prefix) {

// Send WITHDRAW message to all peers

}

Step 4: Integrate the BGP Agent into NS2

  1. Modify the Makefile: Append the new BGPAgent class to the NS2 Makefile so as to it acquires compiled with the rest of the simulator.
  2. Recompile NS2:

make clean

make

Step 5: Create a Tcl Script to Simulate BGP

When the BGP protocol is executed and compiled, and make a Tcl script to mimic a network using BGP.

Example Tcl Script:

# Create a simulator object

set ns [new Simulator]

# Define the topology

set val(chan)   Channel/WiredChannel

set val(ll)     LL

set val(ifq)    Queue/DropTail/PriQueue

set val(ifqlen) 50

set val(ant)    Antenna/OmniAntenna

set val(nn)     5

set val(stop)   50.0

set val(rp)     BGP   ;# Border Gateway Protocol

# Initialize the topology object

set topo [new Topography]

$topo load_flatgrid 1000 1000

# Create nodes (representing AS routers)

for {set i 0} {$i < $val(nn)} {incr i} {

set node_($i) [$ns node]

}

# Establish links between nodes (representing AS connections)

$ns duplex-link $node_(0) $node_(1) 1Mb 10ms DropTail

$ns duplex-link $node_(1) $node_(2) 1Mb 10ms DropTail

$ns duplex-link $node_(2) $node_(3) 1Mb 10ms DropTail

$ns duplex-link $node_(3) $node_(4) 1Mb 10ms DropTail

# Set up BGP sessions between the routers

$ns at 0.5 “$node_(0) establishBGPSession $node_(1)”

$ns at 0.5 “$node_(1) establishBGPSession $node_(2)”

$ns at 0.5 “$node_(2) establishBGPSession $node_(3)”

$ns at 0.5 “$node_(3) establishBGPSession $node_(4)”

# Start advertising routes

$ns at 1.0 “$node_(0) advertiseRoute 10.0.0.0/8 1”

$ns at 1.5 “$node_(1) advertiseRoute 20.0.0.0/8 2”

# Simulation end

$ns at $val(stop) “stop”

$ns at $val(stop) “exit 0”

proc stop {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

}

# Run the simulation

$ns run

Step 6: Run the Simulation

  1. We can save the Tcl script like bgp_example.tcl.
  2. Open a terminal and navigate to the directory in which we can saved the Tcl script.
  3. Run the simulation using the below command:

ns bgp_example.tcl

Step 7: Analyse the Results

  • We can use trace files and the network animator (NAM) to estimate the performance of the BGP protocol, concentrating on parameters like the route convergence time, policy enforcement, and route advertisement behaviour.
  • Analyse how efficiently BGP manages routing among several ASes and how policy-based routing affects path selection.

Additional Considerations

  • Routing Policies: Execute and test with various BGP routing policies to observe how these affect route selection and network behaviour.
  • Performance Comparison: Compare the performance of the BGP execution with other routing protocols to compute its scalability and efficiency.

We applied a sequential process to Border gateway protocol, which was then executed and analysed using the simulation tool ns2. If you want further details regarding this, we will offered. You can receive customized assistance from our team for the implementation of Border Gateway Protocol in NS2. We will provide guidance at every stage of the process. Additionally, explore a variety of optimal project topics available at ns2project.com. Our services also include support for the performance analysis of your project