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How to Calculate Network Bandwidth in omnet++

To calculate the network bandwidth in OMNeT++ requires us to estimating the number of data transferred through a network link within a given time period. Bandwidth is usually expressed in bits per second (bps), and it represents the capacity of the network to manage traffic. This procedure offered the demonstration to calculate network bandwidth:

Steps to Calculate Network Bandwidth in OMNeT++:

  1. Set Up the Network Model:
    • In OMNeT++, use NED file to state the network topology as well as creating nodes and connecting them with network links that have certain data rates (e.g., 10 Mbps, 100 Mbps).
  2. Implement Traffic Generation:
    • Generate network traffic by using or creating modules. Simulate the data flow through the network by using Applications like UdpApp, TcpApp, or custom traffic generators.
    • To examine the bandwidth of the network like sending a stream of data packets from one node to another, we have to design the traffic generation.
  3. Measure the Amount of Data Transferred:
    • To compute bandwidth, you need to measure the total amount of data (in bits) that has been successfully conveyed over a specific period.
  4. Calculate Bandwidth:
    • Bandwidth can be calculated by dividing the total amount of data transferred by the time it took to transfer that data.
    • Use the following formula: Bandwidth=Total Data Transferred (in bits)Time (in seconds)\text{Bandwidth} = \frac{\text{Total Data Transferred (in bits)}}{\text{Time (in seconds)}}Bandwidth=Time (in seconds)Total Data Transferred (in bits)​

Example Implementation:

Here’s an example of how to measure network bandwidth in a point-to-point link scenario:

#include <omnetpp.h>

using namespace omnetpp;

class BandwidthModule : public cSimpleModule {

private:

int64_t totalBitsSent;  // Total number of bits sent

simtime_t startTime;    // Start time of the measurement period

protected:

virtual void initialize() override {

totalBitsSent = 0;

startTime = simTime();

// Schedule first packet send

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

}

virtual void handleMessage(cMessage *msg) override {

if (msg->isSelfMessage()) {

// Simulate sending a packet

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

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

totalBitsSent += bitsSent;

cMessage *packet = new cMessage(“dataPacket”);

send(packet, “out”);

// Schedule next packet send

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

delete msg;

} else {

// Packet received

delete msg;

}

}

virtual void finish() override {

// Calculate and print bandwidth

simtime_t endTime = simTime();

double bandwidth = totalBitsSent / (endTime – startTime).dbl(); // in bits per second (bps)

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

EV << “Time Taken: ” << (endTime – startTime).dbl() << ” seconds\n”;

EV << “Calculated Bandwidth: ” << bandwidth / 1e6 << ” Mbps\n”;

}

};

Define_Module(BandwidthModule);

Explanation:

  • initialize() Function:
    • Initializes the variables totalBitsSent and startTime. It also schedules the first packet transmission.
  • handleMessage() Function:
    • Manages both self-messages (specifying it’s time to send another packet) and incoming packets.
    • For every packet sent, the module estimates the size in bits and adds it to the total.
  • finish() Function:
    • At the end of the simulation, the function calculates the total time elapsed and the total bits sent.
    • It then use the formula to calculates the bandwidth and prints it out.
  1. Run the Simulation:
  • Compile the OMNeT++ project and run the simulation.
  • Examine the console output or logs to view the calculated bandwidth once the simulation ends.
  1. Analyze and Interpret Results:
  • The calculated bandwidth gives you an idea of the network’s capacity to manage data. You can relate it with the theoretical maximum bandwidth of the link to define if there are bottlenecks or inefficiencies.

Additional Considerations:

  • Traffic Type: The type of traffic (e.g., TCP, UDP) and its characteristics (e.g., packet size, inter-arrival time) can disturb the measured bandwidth.
  • Link Characteristics: Make sure that the link’s data rate (datarate attribute in the NED file) is set properly to replicate the network’s capacity.
  • Network Conditions: During the simulation, factors like congestion, packet loss, and delay can impact the actual bandwidth measured.

In this procedure, we completely focused and learned the calculation of Network Bandwidth and its functionalities that are needed in the OMNeT++.

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