How to Calculate Network Capacity in omnet++

To calculate the network capacity in OMNeT++, we have to state the maximum number of data which can be managed through a certain period in the network. Network capacity is frequently measured in bits per second (bps) and can be influenced by factors like link data rates, network topology, traffic patterns, and protocol overhead.

Steps to Calculate Network Capacity in OMNeT++:

1. Set Up the Network Model:
   • Use NED files to state the network topology in OMNeT++. It includes setting up nodes, links with certain data rates, and configuring any essential routing protocols.
2. Implement Traffic Generation:
   • Simulate the data flow through the network by using modules like UdpApp, TcpApp, or custom traffic generators. The traffic should be configured to fully utilize the network, pushing it to its capacity limits.
3. Measure Data Throughput:
   • Throughput is the actual rate at which data is successfully transmitted over the network. We need to compute the total throughput over the network to measure the network capacity.
4. Calculate Network Capacity:
   • Calculate the total throughput across all links and nodes in optimal traffic conditions where it fully utilized without congestion only to estimate the network capacity.

Example Implementation: Measuring Network Throughput

Sample of how to calculate network capacity by measuring the total throughput in OMNeT++:

#include <omnetpp.h>

using namespace omnetpp;

class ThroughputModule : public cSimpleModule {

private:

int64_t totalBitsSent;  // Total number of bits sent across the network

simsignal_t throughputSignal;  // Signal to record throughput

protected:

virtual void initialize() override {

totalBitsSent = 0;

throughputSignal = registerSignal(“throughputSignal”);

// Schedule the first packet send

scheduleAt(simTime() + par(“sendInterval”).doubleValue(), new cMessage(“sendPacket”));

}

virtual void handleMessage(cMessage *msg) override {

if (strcmp(msg->getName(), “sendPacket”) == 0) {

// Simulate sending a packet

int packetSize = par(“packetSize”).intValue();  // in bytes

int64_t bitsSent = packetSize * 8;  // Convert to bits

totalBitsSent += bitsSent;

// Schedule the next packet send

scheduleAt(simTime() + par(“sendInterval”).doubleValue(), new cMessage(“sendPacket”));

delete msg;

} else if (strcmp(msg->getName(), “dataPacket”) == 0) {

// Packet received at destination

// Optionally, you could add logic here to calculate per-link throughput

delete msg;

}

}

virtual void finish() override {

// Calculate total simulation time

simtime_t totalTime = simTime();

// Calculate and record throughput (bits per second)

double throughput = (double)totalBitsSent / totalTime.dbl();  // in bps

emit(throughputSignal, throughput);

EV << “Total Bits Sent: ” << totalBitsSent << ” bits\n”;

EV << “Total Simulation Time: ” << totalTime << ” seconds\n”;

EV << “Calculated Network Throughput (Capacity): ” << throughput / 1e6 << ” Mbps\n”;

}

};

Define_Module(ThroughputModule);

Explanation:

• ThroughputModule:
  • totalBitsSent: In the course of simulation, we can tracks the entire amount of bits sent through the network.
  • throughputSignal: At the end of the simulation, we have to emit the computed throughput by registering a signal.
• initialize() Function:
  • Initializes the total bits sent and schedules the first packet transmission.
• handleMessage() Function:
  • Simulates the sending of packets and apprises the total bits sent.
  • If needed, we can expand this to estimate per-link or per-node throughput.
• finish() Function:
  • At the end of the simulation, the function computes the overall network throughput by dividing the total bits sent by the total simulation time.
  • The result is logged and can be interpreted as the network’s capacity in Mbps (Megabits per second).

5. Run the Simulation:

• Compile and run the OMNeT++ project. The simulation will calculate the total bits sent across the network and use this data to estimate the network capacity.

6. Analyze and Interpret Results:

• The calculated throughput gives you an approximation of the network’s capacity as per the given conditions. If the network is fully utilized without congestion, this value approximates the network’s capacity.

Additional Considerations:

• Link Data Rates: To exactly reflect the network’s capacity, we have to make sure that the links in the network are configured with realistic data rates (data rate attribute in the NED files).
• Traffic Patterns: The traffic pattern (e.g., constant bit rate, bursty traffic) can affect throughput measurements. Use traffic which increases link utilization to precisely measure capacity.
• Congestion and Overhead: Consider factors like congestion, packet loss, and protocol overhead, which can ease the effective capacity of the network.

In this procedure, we provided the detailed guide on how to calculate the network capacity in OMNeT++ and their execution using samples to help you understand it. If you need any information about this calculation, we will provide them.

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