How to Start Link Aggregation Control Protocol Using OMNeT++

To start a Link Aggregation Control Protocol (LACP) project using OMNeT++, we want to replicate the combination of numerous network links offering higher bandwidth and redundancy among the network devices like switches. LACP is small portion of the IEEE 802.1AX standard that supports to automatically devices transfer and handle the link aggregation which is normally use Ethernet interfaces.

OMNeT++ environment and the INET framework offer the essential tools to replicate network protocols, but LACP doesn’t directly have support for executing in INET framework, thus we want to make custom modules or adapt existing modules replicating the functionality of LACP.

Following is a stepwise approach on how to start a LACP project using OMNeT++.

Steps to Start LACP Projects in OMNeT++

Step 1: Install OMNeT++ and INET Framework

  1. Install OMNeT++:
    • We should download the new version of OMNeT++ environment on the system.
    • Adhere to the installation guidance according to the OS.
  2. Install INET Framework:
    • The INET offers several network simulation models with Ethernet and network devices such as switches and routers.
    • Copy INET using GitHub:

git clone https://github.com/inet-framework/inet.git

    • Also, we need to import the INET framework to OMNeT++ with the support of OMNeT++ Module Manager.

Step 2: Create a New OMNeT++ Project for LACP

  1. Create a New OMNeT++ Project:
    • Navigate File > New > OMNeT++ Project and make a new project like LACP_Project in OMNeT++.
  2. Set Up the Network Topology:
    • Make a network topology, which has several network interfaces or devices that can be supported for Link Aggregation like switches or routers. Two switches including two or more aggregated links will be enough for a basic LACP simulation.

Example of a basic LACP topology:

network LACPNetwork {

submodules:

switch1: EthernetSwitch;

switch2: EthernetSwitch;

connections:

switch1.eth[0] <–> EthernetInterface <–> switch2.eth[0];

switch1.eth[1] <–> EthernetInterface <–> switch2.eth[1];

}

In this topology:

  • EthernetSwitch is a switch component.
  • EthernetInterface denotes the network interface which is utilised by the switches.
  • switch1 and switch2 are linked by two links which will be combined by LACP.

Step 3: Implementing LACP Protocol

While LACP doesn’t directly have support for executing in the INET Framework then we will make a custom module, which simulates Link Aggregation. The main functionality to execute the following:

  • LACP Data Units (LACPDUs): These are the control packets, which LACP utilises to transfer, handle, and observe the link aggregation groups (LAGs).
  • Link Aggregation Group (LAG): A set of physical links among the two devices, which are considered like a single logical link.
  • LACP Protocol States: The protocol functions in diverse states like:
    • Detached: The link is not portion of any aggregation group.
    • Waiting: The link is staying to connect with group.
    • Negotiating: LACP is transferring link aggregation.
    • Aggregated: The link is portion of an active aggregation group.

Create a Custom Module for LACP

We can make a custom module like LacpModule, which denotes a switch or device that assists LACP. Below is a structure for how to execute the protocol:

  1. Define the Module Class: Make a LacpModule class, which prolongs the cSimpleModule for each switch.

class LacpModule : public cSimpleModule {

private:

bool isActive; // Indicates if the LAG is active

std::vector<cGate *> links; // Physical links participating in LAG

protected:

virtual void initialize() override {

isActive = false;

// Initialize links, states, and timers

links.push_back(gate(“eth[0]”));

links.push_back(gate(“eth[1]”));

}

virtual void handleMessage(cMessage *msg) override {

if (msg->isSelfMessage()) {

// Process LACP timers or state transitions

handleLacpTimer();

} else {

// Handle incoming LACP Data Units (LACPDUs)

processLacpDU(msg);

}

}

void handleLacpTimer() {

// Periodically send LACPDU to manage the aggregation group

if (!isActive) {

sendLacpDU();

}

}

void processLacpDU(cMessage *msg) {

// Process incoming LACP Data Units (LACPDUs)

if (msg->getKind() == LACPDU_TYPE) {

// Check the state of the LACPDU and update aggregation state

processLacpNegotiation(msg);

}

}

void processLacpNegotiation(cMessage *msg) {

// Handle the negotiation process and determine if the link should be aggregated

if (isActive) {

// Add the link to the aggregation group and mark it as active

EV << “Link aggregated and active.\n”;

} else {

// Mark the link as waiting or detached

EV << “Link in negotiation state.\n”;

}

}

void sendLacpDU() {

// Send LACP Data Unit (LACPDU) to the connected switches

cMessage *lacpDU = new cMessage(“LACPDU”);

lacpDU->setKind(LACPDU_TYPE);

send(lacpDU, “out”);

}

};

In this simple execution:

  • isActive monitors whether the link aggregation is functioning or not.
  • links saves the physical links that is included within aggregation.
  • handleLacpTimer() handles the timing to transmit LACPDUs.
  • processLacpDU() executes incoming LACPDUs from other switches to transfer link aggregation.
  1. Define LACP Data Unit (LACPDU):
    • We can specify the structure of the LACP Data Unit (LACPDU) to take negotiation data among the switches.
    • Every single LACPDU will be contained data like system priority, port number, LAG state, and timers.

Example of a simplified LACPDU message class:

class LacpDU : public cMessage {

public:

int systemPriority;

int portNumber;

bool aggregationState; // True if aggregated, false otherwise

LacpDU(const char *name = nullptr) : cMessage(name) {

systemPriority = 0;

portNumber = -1;

aggregationState = false;

}

};

In this class:

  • systemPriority: It denotes the precedence of the system for selection purposes.
  • portNumber: In the LAG, signifies the physical port volume of the link.
  • aggregationState: Denotes the state of the link whether it is portion of an aggregation group.

Step 4: Configure the Simulation

  1. Configure Network Settings:
    • We want to set the simulation metrics relevant to LACP like LACP timers, aggregation settings, and network topology using the omnetpp.ini file.

Example omnetpp.ini configuration:

network = LACPNetwork

sim-time-limit = 100s

[Config LacpConfig]

*.switch1.typename = “LacpModule”

*.switch2.typename = “LacpModule”

# Set LACP parameters

*.switch1.aggregationState = true

*.switch1.lacpHelloTime = 1s

*.switch2.lacpHelloTime = 1s

Now:

  • aggregationState finds whether the link aggregation is functioning or not.
  • lacpHelloTime configurs the hello time for LACP negotiation.
  1. Traffic Generation:
    • Configure the network traffic among linked hosts. We need to utilise the UDP or TCP applications for checking the link aggregation enhances the bandwidth and offers redundancy.

Example traffic configuration:

*.host1.app[0].typename = “UdpBasicApp”

*.host1.app[0].destAddr = “host2”

*.host1.app[0].startTime = 1s

*.host1.app[0].messageLength = 100B

*.host1.app[0].sendInterval = 0.5s

Step 5: Run the Simulation

  1. Build the Project:
    • In OMNeT++, execute the project by selecting Build
  2. Run the Simulation:
    • Make use of Tkenv or Qtenv, we need to execute the simulation.
    • Observe the LACP protocol’s behavior since the switches transfer link aggregation.
  3. Monitor LACP Negotiation:
    • Observe the sending and receiving of LACPDUs to utilise EV logging.
    • Monitor how the aggregation state of the links are modifies rely on negotiation progression.

Step 6: Extend the Simulation

  1. Test Different Configurations:
    • Test with various link aggregation settings like inserting or eliminating the physical links, modifying system priorities, or adapting the hello time.
  2. Evaluate Link Failures:
    • We have to mimic link failures and then monitor how the aggregation group responses. Confirm that traffic even flow via remaining aggregated links.
  3. Scalability:
    • Execute the functionality of LACP including a higher volume of switches and aggregated links.

Conclusion

Replicating Link Aggregation Control Protocol (LACP) we will make custom modules, which manage the LACP negotiation, handle Link Aggregation Groups (LAGs), and execute the LACP Data Units (LACPDUs) using OMNeT++. After configuring the network topology and executing LACP logic then we can execute simulations modifying how link aggregation functions, enhancing bandwidth and redundancy among the network devices.

We have outlined the structure with OMNeT++ -specific content, including simulation, implementation with code snippets for replicating Link Aggregation Control Protocol Projects. Additional details on this topic will be made available.

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