How to Implement LAN Protocols in NS2

To implement the LAN (Local Area Network) protocols in ns2, we have to simulate the protocol and its features which are often used inside the LAN environment. It is usually works at Layer 2 (Data Link Layer) and Layer 3 (Network Layer) of the OSI model. Examples include Ethernet (Layer 2), VLANs (Virtual LANs), Spanning Tree Protocol (STP), and IP routing within a LAN (Layer 3). The given procedure will guide you through the implementation of these protocols in ns2:

Step-by-Step Implementation:

Step 1: Define the LAN Protocol Requirements

State the specific LAN protocol you want to execute or simulate. Examples such as:

  • Ethernet: Simulating basic Ethernet frames and switches.
  • VLANs: Implementing VLAN tagging and communication amongst VLANs.
  • Spanning Tree Protocol (STP): Preventing loops in Ethernet networks.
  • IP Routing in LAN: Routing IP packets inside a LAN environment.

Step 2: Set Up NS2

Make certain to install the ns2 on your computer. Validate it by executing the simulation. Ns2 has in-built support for simple Ethernet-based actions and IP routing, yet we might need to execute or expand the functionality for more difficult LAN protocols like VLANs or STP.

Step 3: Implement the LAN Protocol in C++

  1. Create the LAN Protocol Agent Class

Here’s a basic structure for executing a basic Ethernet-based LAN protocol. This instance offers the skeleton for a protocol that could replicate Ethernet switching with basic frame forwarding.

#include <agent.h>

#include <packet.h>

#include <trace.h>

#include <address.h>

#include <map>

class LANProtocolAgent : public Agent {

public:

LANProtocolAgent();

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

void forwardFrame(Packet* p);

void handleBroadcast(Packet* p);

protected:

std::map<int, int> macTable_; // MAC Address -> Port

int port_; // Port number for this agent

};

// Constructor

LANProtocolAgent::LANProtocolAgent() : Agent(PT_UDP), port_(0) {

// Initialization code here

}

// Packet reception

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

hdr_cmn* cmnh = hdr_cmn::access(p);

int dest_mac = cmnh->next_hop_;

if (macTable_.find(dest_mac) != macTable_.end()) {

forwardFrame(p);

} else {

handleBroadcast(p);

}

}

// Forward Ethernet frame to the correct port

void LANProtocolAgent::forwardFrame(Packet* p) {

hdr_cmn* cmnh = hdr_cmn::access(p);

int dest_mac = cmnh->next_hop_;

int next_port = macTable_[dest_mac];

// Forward the frame to the correct port

send(p, next_port);

}

// Handle broadcast frames (e.g., ARP requests)

void LANProtocolAgent::handleBroadcast(Packet* p) {

// Broadcast the frame to all ports except the one it came from

for (auto& entry : macTable_) {

if (entry.second != port_) {

send(p->copy(), entry.second);

}

}

Packet::free(p);

}

  1. Implement VLAN Support (Optional)

Expand the LANProtocolAgent by replicating VLANs to support VLAN tagging and filtering. This would involve attaching logic to tag frames with VLAN IDs and only forward them to the proper VLANs.

class LANProtocolAgentVLAN : public LANProtocolAgent {

public:

void handleVLAN(Packet* p, int vlan_id);

protected:

std::map<int, std::vector<int>> vlanTable_; // VLAN ID -> List of Ports

};

// Handle VLAN tagged frames

void LANProtocolAgentVLAN::handleVLAN(Packet* p, int vlan_id) {

if (vlanTable_.find(vlan_id) != vlanTable_.end()) {

for (int port : vlanTable_[vlan_id]) {

send(p->copy(), port);

}

}

Packet::free(p);

}

Step 4: Integrate the LAN Protocol into NS2

  1. Modify the Makefile: Include your new LANProtocolAgent class (and optionally LANProtocolAgentVLAN for VLAN support) to the NS2 Makefile so that it gets compiled with the rest of the simulator.
  2. Recompile NS2:

make clean

make

Step 5: Create a Tcl Script to Simulate the LAN Protocol

After the LAN protocol is compiled, set up a Tcl script to replicate a LAN environment using your custom protocol.

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(stop)   50.0

# Initialize the topology object

set topo [new Topography]

$topo load_flatgrid 500 500

# Create nodes representing switches and hosts

set switch1 [$ns node]

set switch2 [$ns node]

set host1 [$ns node]

set host2 [$ns node]

# Establish links between switches and hosts

$ns duplex-link $switch1 $switch2 100Mb 1ms DropTail

$ns duplex-link $switch1 $host1 100Mb 1ms DropTail

$ns duplex-link $switch2 $host2 100Mb 1ms DropTail

# Attach LAN protocol agents to switches

set lan1 [new Agent/LANProtocolAgent]

set lan2 [new Agent/LANProtocolAgent]

$ns attach-agent $switch1 $lan1

$ns attach-agent $switch2 $lan2

# Set up traffic sources and sinks

set udp [new Agent/UDP]

set null [new Agent/Null]

$ns attach-agent $host1 $udp

$ns attach-agent $host2 $null

$ns connect $udp $null

# Start the simulation

$ns at 0.0 “$udp start”

$ns at $val(stop) “stop”

$ns at $val(stop) “exit 0”

proc stop {} {

global ns

$ns flush-trace

exit 0

}

# Run the simulation

$ns run

Step 6: Run the Simulation

  1. Save the Tcl script (lan_protocol_simulation.tcl).
  2. Open a terminal and navigate to the directory where you saved the Tcl script.
  3. Use the below command to run the simulation:

ns lan_protocol_simulation.tcl

Step 7: Analyze the Results

  • Use trace files and the network animator (NAM) to evaluate the performance of your LAN protocol concentrates on metrics includes frame delivery, network overhead, and correct VLAN tagging and forwarding.
  • Inspect how well your protocol manages various traffic patterns and network topologies.

Additional Considerations

  • Spanning Tree Protocol (STP): To prevent loops in your LAN, you could execute a basic version of STP that restricts particular ports to uphold a loop-free topology.
  • Advanced VLAN Features: Implement latest VLAN features like inter-VLAN routing and dynamic VLAN allocation in terms of MAC addresses.
  • Performance Optimization: Enhance your protocol for performance depends on efficient frame forwarding and less latency.

Overall, we completely guided you to understand and set up the simulation to implement the LAN protocol with the help of Network Simulation 2 (ns2). You can optimize the protocol by following the given advanced considerations. We will present any additional information on this topic, if you need. We provide the best results for implementing LAN Protocols in NS2, and our topic support is backed by ns2project.com.