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How to Implement Link Aggregation Control Protocol in OMNeT++

To implement the Link Aggregation Control Protocol (LACP) in OMNeT++ is part of the IEEE 802.1AX standard (previously IEEE 802.3ad). It is known as a Link Aggregation Group used to bundle multiple physical network links into a single logical link. It gives redundancy and rises bandwidth by allowing traffic to be distributed across numerous links.

To implement LACP in OMNeT++ using the INET framework, need to mimic the behaviour of LACP, including the distribution of traffic across the aggregated links and the negotiation method to form link aggregation groups.

Step-by-Step Implementations:

Step 1: Set Up OMNeT++ and INET Framework

  1. Install OMNeT++:
    • Make sure OMNeT++ is installed on the system.
  2. Install the INET Framework:
    • Download and install the INET Framework, which offers several networking protocols and models, including Ethernet and switching models. INET can be downloaded from the INET GitHub repository.

Step 2: Create a New OMNeT++ Project

  1. Create the Project:
    • Open OMNeT++ and make a new OMNeT++ project through File > New > OMNeT++ Project.
    • Name the project like LACPSimulation and set up the project directory.
  2. Set Up Project Dependencies:
    • Make sure the project references the INET Framework by right-clicking on the project in the Project Explorer, navigating to Properties > Project References, and verifying the INET project.

Step 3: Define the Network Topology

  1. Create a NED File:
    • By using the NED language to define the network topology. This topology will contain switches with multiple physical links among them that can be bundled into a LAG.

Example:

network LACPNetwork

{

parameters:

int numLinks = default(2); // Number of physical links to aggregate

submodules:

switchA: EtherSwitch {

@display(“i=block/switch”);

}

switchB: EtherSwitch {

@display(“i=block/switch”);

}

hostA: StandardHost {

@display(“i=block/host”);

}

hostB: StandardHost {

@display(“i=block/host”);

}

connections allowunconnected:

for i=0..numLinks-1 {

switchA.ethg++ <–> Eth10Gbps <–> switchB.ethg++;

}

hostA.ethg++ <–> Eth10Gbps <–> switchA.ethg++;

hostB.ethg++ <–> Eth10Gbps <–> switchB.ethg++;

}

  1. Configure Network Parameters:
    • Set up needed link parameters like delay, bandwidth, and packet loss to simulate a realistic network setting.

Step 4: Implement the Link Aggregation Control Protocol (LACP)

LACP includes negotiating the formation of a LAG and managing the distribution of traffic across the combined links.

  1. Create the LACP Module in NED

Example (in NED):

simple LACP

{

parameters:

@display(“i=block/network2”);

gates:

inout lowerLayerIn[];

inout lowerLayerOut[];

}

  1. Implement LACP in C++

The given below is basic structure for implementing LACP in C++:

#include “inet/common/INETDefs.h”

#include “inet/linklayer/ethernet/EtherFrame_m.h”

#include “inet/common/packet/Packet.h”

#include “inet/networklayer/common/InterfaceTable.h”

#include “inet/linklayer/common/MACAddress.h”

#include “inet/linklayer/common/Ieee802Ctrl.h”

class LACP : public cSimpleModule

{

private:

InterfaceTable *interfaceTable;

std::vector<int> activeLinks; // Indices of active links in the LAG

cMessage *lacpTimer;

protected:

virtual void initialize() override;

virtual void handleMessage(cMessage *msg) override;

void sendLACPDU();

void processLACPDU(Packet *packet);

void updateLAG();

};

Define_Module(LACP);

void LACP::initialize() {

interfaceTable = getModuleFromPar<InterfaceTable>(par(“interfaceTableModule”), this);

 

// Schedule periodic LACPDU broadcasts

lacpTimer = new cMessage(“LACP_Timer”);

scheduleAt(simTime() + 1, lacpTimer);

}

void LACP::handleMessage(cMessage *msg) {

if (msg == lacpTimer) {

sendLACPDU();

scheduleAt(simTime() + 1, lacpTimer);  // Reschedule LACPDU broadcast

} else {

Packet *packet = check_and_cast<Packet *>(msg);

processLACPDU(packet);

}

}

void LACP::sendLACPDU() {

for (int i = 0; i < gateSize(“lowerLayerOut”); i++) {

Packet *lacpPacket = new Packet(“LACPDU”);

auto ethFrame = makeShared<EtherFrame>();

ethFrame->setDest(MACAddress::BROADCAST_ADDRESS);

ethFrame->setSrc(interfaceTable->getInterface(i)->getMacAddress());

lacpPacket->insertAtBack(ethFrame);

send(lacpPacket, “lowerLayerOut”, i);

}

}

void LACP::processLACPDU(Packet *packet) {

auto ethFrame = packet->peekAtFront<EtherFrame>();

// Example: Activate the link if the LACPDU is valid and conditions are met

int receivingPort = packet->getArrivalGate()->getIndex();

if (std::find(activeLinks.begin(), activeLinks.end(), receivingPort) == activeLinks.end()) {

activeLinks.push_back(receivingPort);

updateLAG();

}

delete packet;

}

void LACP::updateLAG() {

// Logic to update the LAG based on activeLinks

// For example, configure traffic distribution across activeLinks

}

Step 5: Configure the Simulation

  1. Set Up the Simulation in omnetpp.ini:
    • State the simulation parameters like the network to use, simulation time, and LACP behaviour.

Example:

[General]

network = LACPNetwork

sim-time-limit = 100s

**.scalar-recording = true

**.vector-recording = true

# LACP Configuration

**.switch*.hasLACP = true  # Enable LACP on all switches

  1. Compile and Run the Simulation:
    • Make sure everything is correctly implemented and compiled. Run the simulation using OMNeT++’s IDE or command line.

Step 6: Analyse the Results

  1. Monitor LACP Behaviour:
    • Monitor how LACP packets are replaced between switches and how links are combined to form a LAG.
  2. Evaluate Performance:
    • Analyse key performance metrics like the time taken to form a LAG, the use the aggregated links, and the overall throughput.
    • Scalars and Vectors: To record and analyse scalar and vector data, such as the number of LACPDUs exchanged, the number of active links in the LAG, and the traffic distribution across the links by using OMNeT++ tools.

Step 7: Optimize and Extend the Protocol

  1. Address Any Issues:
    • If the simulation exposes any issues like incorrect link aggregation, packet loss, adjust the LACP logic or network configuration as required.
  2. Extend the Protocol:
    • Implement supplementary LACP features like load balancing algorithms, support for LACP priority, or LACP state machines for more exact simulation of LACP behaviour.

Hence, we had demonstrate how to create the LACP module in NED file, implement in C++, configure the simulation, and optimize the protocol in Link Aggregation Control Protocol using OMNeT++ tool. We will give more appropriate information about this topic using other tool.

Feel free to reach out to us for simulation results on Link Aggregation Control Protocol using the OMNeT++ tool for your projects.

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