How to Implement Layer 3 Routed Protocol in NS2

To implement the Layer 3 routed protocol in NS2, we have to simulate a protocol that functions at the network layer (Layer 3) of the OSI model in which manages packet forwarding according to the IP addresses. Typical instances of Layer 3 routing protocols include OSPF, RIP, and BGP. Here, we provide the general type of implementation in ns2:

Step-by-Step Implementation:

Step 1: Understand Layer 3 Routing

Layer 3 protocols are accountable for stating the best path for data to move through networks. They involve routing decisions depends on IP addresses and consume routing tables to handle the paths data should take.

Step 2: Set Up NS2

Make certain that you have ns2 installed on your system. You can download it from the NS2 website and follow the installation instructions.

Step 3: Implement a Layer 3 Routing Protocol

  1. Create the Routing Agent Class (C++)

Execute the Layer 3 routing logic by configuring the new C++ class in ns2 which should manage the given below:

  • Routing Table Maintenance: Maintain a routing table that stores the best path to each destination.
  • Packet Forwarding: Forward packets depends on the routing table.

Here’s a basic structure:

#include <agent.h>

#include <packet.h>

#include <trace.h>

#include <address.h>

#include <map>

class Layer3RoutingAgent : public Agent {

public:

Layer3RoutingAgent();

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

void forwardPacket(Packet* p);

void updateRoutingTable(int dest, int nextHop);

protected:

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

};

// Constructor

Layer3RoutingAgent::Layer3RoutingAgent() : Agent(PT_UDP) {

// Initialization code here

}

// Packet reception

void Layer3RoutingAgent::recv(Packet* p, Handler* h) {

hdr_ip* iph = hdr_ip::access(p);

int dest = iph->dst();

if (routingTable_.find(dest) != routingTable_.end()) {

forwardPacket(p);

} else {

// Implement route discovery or handling

}

}

// Forward packet to the selected next hop

void Layer3RoutingAgent::forwardPacket(Packet* p) {

hdr_ip* iph = hdr_ip::access(p);

int nextHop = routingTable_[iph->dst()];

// Code to forward the packet to the next hop

}

// Update the routing table with a new route

void Layer3RoutingAgent::updateRoutingTable(int dest, int nextHop) {

routingTable_[dest] = nextHop;

}

  1. Integrate the Routing Agent into NS2
  1. Modify the Makefile: Include the new Layer3RoutingAgent class to the NS2 Makefile so that it gets compiled with the remaining of the simulator.
  2. Recompile NS2:

make clean

make

Step 4: Create a Tcl Script to Simulate the Layer 3 Protocol

Once the protocol is compiled, we have to build a Tcl script to simulate a network using this Layer 3 protocol.

Example Tcl Script:

# Create a simulator object

set ns [new Simulator]

# Define the topology

set val(chan)   Channel/WirelessChannel

set val(prop)   Propagation/TwoRayGround

set val(netif)  Phy/WirelessPhy

set val(mac)    Mac/802_11

set val(ifq)    Queue/DropTail/PriQueue

set val(ll)     LL

set val(ant)    Antenna/OmniAntenna

set val(ifqlen) 50

set val(nn)     10

set val(x)      1000

set val(y)      1000

set val(stop)   100.0

set val(rp)     Layer3Routing   ;# Custom Layer 3 routing protocol

# Initialize the topology object

set topo [new Topography]

$topo load_flatgrid $val(x) $val(y)

# Create the God object

create-god $val(nn)

# Configure the nodes

$ns node-config -adhocRouting $val(rp) \

-llType $val(ll) \

-macType $val(mac) \

-ifqType $val(ifq) \

-ifqLen $val(ifqlen) \

-antType $val(ant) \

-propType $val(prop) \

-phyType $val(netif) \

-channelType $val(chan) \

-topoInstance $topo \

-agentTrace ON \

-routerTrace ON \

-macTrace ON \

-movementTrace ON

# Create nodes

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

set node_($i) [$ns node]

}

# Define node positions and movement model

$node_(0) set X_ 100.0; $node_(0) set Y_ 200.0

$node_(1) set X_ 200.0; $node_(1) set Y_ 300.0

$node_(2) set X_ 300.0; $node_(2) set Y_ 400.0

$node_(3) set X_ 400.0; $node_(3) set Y_ 500.0

$node_(4) set X_ 500.0; $node_(4) set Y_ 600.0

# Set up traffic sources

set udp [new Agent/UDP]

$ns attach-agent $node_(0) $udp

set null [new Agent/Null]

$ns attach-agent $node_(4) $null

$ns connect $udp $null

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$cbr set packetSize_ 512

$cbr set interval_ 0.1

$cbr start

# Simulation end

$ns at $val(stop) “stop”

$ns at $val(stop) “$ns nam-end-wireless $val(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 5: Run the Simulation

  1. Save the Tcl script (layer3_example.tcl).
  2. Open a terminal and traverse to the directory where you stored the Tcl script.
  3. Use the given command to run the simulation:

ns layer3_example.tcl

Step 6: Analyze the Results

  • Utilize trace files and the network animator (NAM) to evaluate the performance of the Layer 3 protocol, aiming on metrics includes packet delivery ratio, end-to-end delay, and routing overhead.
  • Test how well the protocol manages route updates, vary in network topology, and numerous traffic patterns.

Additional Considerations

  • Routing Metrics: Agree on the routing metrics you want to use (for instance: hop count, delay, bandwidth) and execute these in your routing logic.
  • Performance Comparison: Compare your custom Layer 3 protocol with standard protocols like OSPF or RIP to assess its efficiency and scalability.

Through this approach, we can understand the basic simulation setup and implementation of Layer 3 (L3) routed protocol and examples using ns2 tool. If needed, we can provide the additional information of this layer for your references.

We carry on  performance analysis for you. We provide top results for Layer 3 Routed Protocol implementation in NS2, get in touch with  ns2project.com