How to Calculate Network Recovery in omnet++
To calculate the network recovery in OMNeT++ has needs to evaluate how quickly and efficiently the network returns to normal operation after a failure and this is a crucial aspect of network resilience and robustness, particularly in dynamic or large-scale networks. The given below are the procedures on how to execute the network recovery in OMNeT++:
Step-by-Step Implementation:
- Define Network Recovery Metrics
To assess network recovery to state the metrics that will be used to measure the recovery process. Common metrics include:
- Recovery Time: The time it takes for the network to restore normal operation after a failure.
- Post-Recovery Throughput: The throughput of the network after recovery, compared to pre-failure levels.
- Packet Loss during Recovery: The number of packets lost during the recovery process.
- Latency Post-Recovery: The latency experienced by packets after the network has recovered.
- Simulate Network Failures
To emulate the failure in the network that has a node or link failure. we schedule this failure to occur at a particular time during the simulation.
Example: Simulating a Failure
void scheduleFailureEvent(cModule* moduleToFail, simtime_t failTime) {
cMessage *failureEvent = new cMessage(“failureEvent”);
scheduleAt(failTime, failureEvent);
moduleToFail->setDisplayString(“p=100,100;i=block/network_red”);
}
void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “failureEvent”) == 0) {
// Simulate failure
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1); // Example: fail node 1
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
delete msg;
} else {
// Normal message processing
send(msg, “out”);
}
}
- Implement Recovery Mechanism
After the failure occurs, execute a recovery mechanism to restore the network’s functionality. This could contain the rerouting traffic, replacing failed components, or re-establishing connections.
Example: Rerouting Traffic for Recovery
void recoverNetwork() {
// Example: Reroute traffic from failed node to an alternative node
cModule *alternativeNode = getParentModule()->getSubmodule(“node”, 2); // Example: use node 2 for recovery
if (!alternativeNode->gate(“in”)->isConnected()) {
alternativeNode->gate(“in”)->connectTo(getParentModule()->getSubmodule(“node”, 0)->gate(“out”));
}
alternativeNode->gate(“out”)->connectTo(getParentModule()->getSubmodule(“node”, 3)->gate(“in”));
}
void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “failureEvent”) == 0) {
// Simulate failure
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1);
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
recoverNetwork(); // Trigger recovery process
delete msg;
} else {
// Process and forward the message
send(msg, “out”);
}
}
- Measure Recovery Time
Recovery time is the duration among the occurrence of the failure and the moment when the network has fully recovered and is operating normally. Recording the time when the failure occurs and when normal operation is restored.
Example: Calculating Recovery Time
simtime_t failureTime;
simtime_t recoveryStartTime;
simtime_t recoveryEndTime;
void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “failureEvent”) == 0) {
// Simulate failure
failureTime = simTime();
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1);
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
recoverNetwork(); // Start the recovery process
recoveryStartTime = simTime(); // Mark the start of recovery
delete msg;
} else {
// If the network has recovered, record the recovery end time
if (isRecovered()) {
recoveryEndTime = simTime();
simtime_t recoveryTime = recoveryEndTime – recoveryStartTime;
EV << “Network recovery time: ” << recoveryTime << ” seconds” << endl;
recordScalar(“Network Recovery Time”, recoveryTime);
}
send(msg, “out”);
}
}
bool isRecovered() {
// Logic to determine if the network has fully recovered
// Example: check if traffic is being routed through the alternative path
return getParentModule()->getSubmodule(“node”, 2)->gate(“out”)->isConnected();
}
- Measure Post-Recovery Performance
After recovery, evaluate the performance of the network to make sure it has returned to its pre-failure levels. This contains thethroughput, latency, and packet delivery ratio.
Example: Measuring Post-Recovery Throughput and Latency
simsignal_t postRecoveryThroughputSignal;
simsignal_t postRecoveryLatencySignal;
void initialize() override {
postRecoveryThroughputSignal = registerSignal(“postRecoveryThroughput”);
postRecoveryLatencySignal = registerSignal(“postRecoveryLatency”);
}
void handleMessage(cMessage *msg) override {
if (isRecovered()) {
// Measure post-recovery performance
simtime_t latency = simTime() – msg->getCreationTime();
emit(postRecoveryLatencySignal, latency);
double throughput = msg->getByteLength() / latency.dbl(); // Bytes per second
emit(postRecoveryThroughputSignal, throughput);
}
send(msg, “out”);
}
- Measure Packet Loss during Recovery
Monitor the number of packets lost during the recovery process. This can be completed by comparing the number of packets sent during recovery with the number received.
Example: Tracking Packet Loss
int packetsSent = 0;
int packetsReceived = 0;
int packetsLost = 0;
void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “failureEvent”) == 0) {
// Simulate failure
failureTime = simTime();
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1);
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
recoverNetwork(); // Start the recovery process
recoveryStartTime = simTime();
delete msg;
} else {
packetsReceived++;
if (isRecovered() && simTime() – recoveryStartTime < 1.0) { // Example: during the first second after recovery
packetsLost++;
}
send(msg, “out”);
}
}
void finish() override {
EV << “Packets sent: ” << packetsSent << endl;
EV << “Packets received: ” << packetsReceived << endl;
EV << “Packets lost during recovery: ” << packetsLost << endl;
recordScalar(“Packets Lost During Recovery”, packetsLost);
}
- Post-Simulation Analysis
After running the simulation, measure the recorded metrics to measure the network’s recovery process. This analysis should include:
- Recovery Time: The total time taken for the network to recover.
- Post-Recovery Performance: Throughput, latency, and packet delivery ratio after recovery.
- Packet Loss: The number of packets lost during the recovery process.
- Example Scenario
The below are the complete samples to incorporate the all the steps above:
class NetworkNode : public cSimpleModule {
private:
simtime_t failureTime;
simtime_t recoveryStartTime;
simtime_t recoveryEndTime;
int packetsSent = 0;
int packetsReceived = 0;
int packetsLost = 0;
simsignal_t postRecoveryThroughputSignal;
simsignal_t postRecoveryLatencySignal;
protected:
virtual void initialize() override {
postRecoveryThroughputSignal = registerSignal(“postRecoveryThroughput”);
postRecoveryLatencySignal = registerSignal(“postRecoveryLatency”);
scheduleFailureEvent(getParentModule()->getSubmodule(“node”, 1), 10.0);
}
void scheduleFailureEvent(cModule* moduleToFail, simtime_t failTime) {
cMessage *failureEvent = new cMessage(“failureEvent”);
scheduleAt(failTime, failureEvent);
moduleToFail->setDisplayString(“p=100,100;i=block/network_red”);
}
virtual void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “failureEvent”) == 0) {
// Simulate failure
failureTime = simTime();
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1);
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
recoverNetwork();
recoveryStartTime = simTime();
delete msg;
} else {
packetsReceived++;
if (isRecovered()) {
recoveryEndTime = simTime();
simtime_t recoveryTime = recoveryEndTime – recoveryStartTime;
EV << “Network recovery time: ” << recoveryTime << ” seconds” << endl;
recordScalar(“Network Recovery Time”, recoveryTime);
// Measure post-recovery performance
simtime_t latency = simTime() – msg->getCreationTime();
emit(postRecoveryLatencySignal, latency);
double throughput = msg->getByteLength() / latency.dbl(); // Bytes per second
emit(postRecoveryThroughputSignal, throughput);
if (simTime() – recoveryStartTime < 1.0) { // Example: during the first second after recovery
packetsLost++;
}
}
send(msg, “out”);
}
}
void recoverNetwork() {
// Example: Reroute traffic from failed node to an alternative node
cModule *alternativeNode = getParentModule()->getSubmodule(“node”, 2);
if (!alternativeNode->gate(“in”)->isConnected()) {
alternativeNode->gate(“in”)->connectTo(getParentModule()->getSubmodule(“node”, 0)->gate(“out”));
}
alternativeNode->gate(“out”)->connectTo(getParentModule()->getSubmodule(“node”, 3)->gate(“in”));
}
bool isRecovered() {
return getParentModule()->getSubmodule(“node”, 2)->gate(“out”)->isConnected();
}
virtual void finish() override {
EV << “Packets sent: ” << packetsSent << endl;
EV << “Packets received: ” << packetsReceived << endl;
EV << “Packets lost during recovery: ” << packetsLost << endl;
recordScalar(“Packets Lost During Recovery”, packetsLost);
}
};
- Post-Simulation Analysis
After running the simulation, use OMNeT++’s analysis tools to investigate the recorded metrics. This analysis will offers the insights into how efficiently and quickly the network recovers from failures, and the effect of recovery on overall network performance.
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