How to Calculate Network Availability in omnet++
To calculate the network availability in OMNeT++ requires estimating the proportion of time the network (or a specific node or link within the network) which is operational and successfully able to deliver packets. To know the reliability and uptime of the network, network availability is a key metric and it can be expressed as a percentage of the total simulation time. omnet-manual.com are leading developers who provide you with best simulation and implementation guidance , share with us your project details to guide you more.
Here’s a calculation of network availability with samples:
Steps to Calculate Network Availability in OMNeT++:
- Define Availability Metric:
- Node Availability: The proportion of time a node is operational.
- Link Availability: The proportion of time a link amongst two nodes is operational.
- Overall Network Availability: The proportion of time the whole network is operational.
- Set Up the Network Model:
- Use NED files to describe the network topology in OMNeT++ which contains setting up nodes, links, and configuring failure and recovery models if you want to simulate nodes or links going down and coming back online.
- Implement Failure and Recovery Models:
- We may need to mimic the scenarios in which their nodes or links can fail and after retrieve. It is accomplished by planning events which disable and re-enable nodes or links in the simulation.
- Track Uptime and Downtime:
- For each node or link, Keep record the time they are operational (uptime) and the time they are down (downtime).
- The obtainability can then be calculated as the ratio of uptime to the total simulation time.
- Calculate Network Availability:
- Availability Formula: Availability=UptimeTotal Simulation Time×100%\text{Availability} = \frac{\text{Uptime}}{\text{Total Simulation Time}} \times 100\%Availability=Total Simulation TimeUptime×100%
Example Implementation: Node Availability
Follow the sample approach to calculate node availability in OMNeT++:
#include <omnetpp.h>
using namespace omnetpp;
class NodeAvailabilityModule : public cSimpleModule {
private:
simtime_t uptime; // Total time the node has been operational
simtime_t downtime; // Total time the node has been down
simtime_t lastChangeTime; // Last time the status changed (up or down)
bool isOperational; // Current status of the node (up or down)
simsignal_t availabilitySignal; // Signal to record availability
protected:
virtual void initialize() override {
uptime = 0;
downtime = 0;
lastChangeTime = simTime();
isOperational = true;
availabilitySignal = registerSignal(“availabilitySignal”);
// Schedule potential failures and recoveries
scheduleAt(simTime() + par(“failureTime”).doubleValue(), new cMessage(“fail”));
}
virtual void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “fail”) == 0) {
// Node failure event
if (isOperational) {
// Node was up, now going down
uptime += simTime() – lastChangeTime;
lastChangeTime = simTime();
isOperational = false;
EV << “Node ” << getId() << ” has failed.\n”;
// Schedule recovery
scheduleAt(simTime() + par(“recoveryTime”).doubleValue(), new cMessage(“recover”));
}
delete msg;
} else if (strcmp(msg->getName(), “recover”) == 0) {
// Node recovery event
if (!isOperational) {
// Node was down, now coming back up
downtime += simTime() – lastChangeTime;
lastChangeTime = simTime();
isOperational = true;
EV << “Node ” << getId() << ” has recovered.\n”;
// Schedule the next failure
scheduleAt(simTime() + par(“failureTime”).doubleValue(), new cMessage(“fail”));
}
delete msg;
}
}
virtual void finish() override {
// If the simulation ends while the node is up, add the remaining time to uptime
if (isOperational) {
uptime += simTime() – lastChangeTime;
} else {
downtime += simTime() – lastChangeTime;
}
// Calculate availability
simtime_t totalTime = uptime + downtime;
double availability = (totalTime > 0) ? (uptime / totalTime).dbl() * 100.0 : 100.0;
// Emit the availability signal
emit(availabilitySignal, availability);
EV << “Node ” << getId() << ” Availability: ” << availability << “%\n”;
}
};
Define_Module(NodeAvailabilityModule);
Explanation:
- NodeAvailabilityModule:
- uptime and downtime: Record the total time the node has been operational and down, respectively.
- lastChangeTime: Trace the last time the node’s status modified (either up or down).
- isOperational: A boolean flag signifying whether the node is currently operational.
- initialize() Function:
- Initializes the uptime, downtime, and schedules the first failure event.
- handleMessage() Function:
- Manages node failure and recovery events. As per the node’s current status, it update the uptime or downtime.
- finish() Function:
- At the end of the simulation, computes the availability as the ratio of uptime to the total time (uptime + downtime). The availability is emitted as a signal and logged.
- Run the Simulation:
- Compile and run the OMNeT++ project. The simulation will calculate the uptime and downtime for each node and define the availability by using this data.
- Analyze and Interpret Results:
- The calculated availability offers a measure of how reliable the node (or network, if applied to all nodes) has been during the simulation. Higher availability represents that the network was operational for a larger portion of the simulation time.
Additional Considerations:
- Link Availability: The same approach can be applied to links amongst nodes by tracking their uptime and downtime.
- Overall Network Availability: For overall network availability, you can consider the network to be available if key nodes or a majority of nodes are operational, and unavailable otherwise.
- Simulating Failures: We need to execute more sophisticated failure model by simulating more difficult failure situations (like correlated failures, cascading failures).
Using this demonstration, we grasped detailed concept on how to calculate the network availability in the OMNeT++ and what is to use in there to implement it. We can help you out, if there is some doubts rises in this process.