How to Calculate Network Failover in omnet++
To calculate the network failover in OMNeT++ has encompasses assessing how efficiently and rapidly the network can reroute traffic when a node, link, or other network component fails. This network failover is a critical aspect of network resilience, make sure that the network can continue to operate even in the face of failures.
Given below is a step-by-step procedure to calculate and analyse network failover in OMNeT++:
Step-by-Step Implementations:
- Define Failover Criteria
Failover normally includes rerouting traffic to an alternative way or node when the major one fails. The key criteria to calculate during failover contain:
- Failover Time: The duration required for the network to detect a failure and redirect traffic.
- Packet Loss during Failover: During the transition the number of packets lost from the failed component to the alternate way.
- Throughput and Latency Post-Failover: The influence of failover on overall network performance.
- Simulate Network Failures
In the OMNeT++ simulation, mimic network failures by purposely disabling a node or link. This can be done using self-messages or timed events.
Example: Simulating a Node or Link 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 node or link failure
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1); // Example: fail node 1
failedModule->bubble(“Node failed”);
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
delete msg;
} else {
// Normal message processing
send(msg, “out”);
}
}
- Implement Failover Mechanism
Implement a mechanism to reroute traffic to alternative paths or nodes after a failure is identified.
Example: Simple Rerouting After Failure
void rerouteTraffic(cMessage *msg) {
int failedNode = 1; // Example: node 1 has failed
int alternativeNode = 2; // Example: reroute to node 2
if (msg->getArrivalGate()->getPreviousGate()->getOwnerModule()->getIndex() == failedNode) {
EV << “Rerouting traffic to node ” << alternativeNode << endl;
send(msg, “out”, alternativeNode);
} else {
send(msg, “out”);
}
}
void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “failureEvent”) == 0) {
// Simulate node failure
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1); // Example: fail node 1
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
delete msg;
} else {
rerouteTraffic(msg);
}
}
- Measure Failover Time
Failover time is the time elapsed among the effective rerouting of traffic and the detection of a failure. We can determine this by recording the simulation time at the moment of failure and the time when traffic begins flowing within the new route.
Example: Calculating Failover Time
simtime_t failureTime;
simtime_t recoveryTime;
void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “failureEvent”) == 0) {
// Simulate failure
failureTime = simTime();
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1); // Example: fail node 1
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
delete msg;
} else {
if (isRerouted(msg)) {
recoveryTime = simTime();
simtime_t failoverTime = recoveryTime – failureTime;
EV << “Failover time: ” << failoverTime << ” seconds” << endl;
recordScalar(“Failover Time”, failoverTime);
}
rerouteTraffic(msg);
}
}
bool isRerouted(cMessage *msg) {
// Logic to determine if the packet has been rerouted
return msg->getArrivalGate()->getIndex() == 2; // Example: rerouted to node 2
}
- Measure Packet Loss during Failover
Track the number of packets that are lost in the failover process. It can be done by observing how many packets reach at the destination and comparing it to the number sent during the failover period.
Example: Tracking Packet Loss
int packetsSent = 0;
int packetsReceived = 0;
int packetsLost = 0;
void handleMessage(cMessage *msg) override {
if (strcmp(msg->getName(), “failureEvent”) == 0) {
failureTime = simTime();
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1);
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
delete msg;
} else if (msg->isSelfMessage()) {
packetsSent++;
rerouteTraffic(msg);
} else {
packetsReceived++;
if (isRerouted(msg) && simTime() – failureTime < recoveryTime – failureTime) {
packetsLost++;
}
send(msg, “out”);
}
}
void finish() override {
EV << “Packets sent: ” << packetsSent << endl;
EV << “Packets received: ” << packetsReceived << endl;
EV << “Packets lost during failover: ” << packetsLost << endl;
recordScalar(“Packets Lost During Failover”, packetsLost);
}
- Analyse Network Performance Post-Failover
Examine the network’s performance metrics, like packet delivery ratio, throughput, and latency to check the impact of the failover on the network’s overall performance after the failover.
- Example Scenario
The following is a comprehensive example of executing and computing network failover in OMNeT++:
class NetworkNode : public cSimpleModule {
private:
simtime_t failureTime;
simtime_t recoveryTime;
int packetsSent = 0;
int packetsReceived = 0;
int packetsLost = 0;
protected:
virtual void initialize() override {
// Schedule a failure event
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 node failure
failureTime = simTime();
cModule *failedModule = getParentModule()->getSubmodule(“node”, 1);
failedModule->gate(“out”)->disconnect();
failedModule->gate(“in”)->disconnect();
delete msg;
} else {
if (msg->isSelfMessage()) {
packetsSent++;
} else {
packetsReceived++;
if (isRerouted(msg)) {
recoveryTime = simTime();
simtime_t failoverTime = recoveryTime – failureTime;
EV << “Failover time: ” << failoverTime << ” seconds” << endl;
recordScalar(“Failover Time”, failoverTime);
}
if (simTime() < recoveryTime && isRerouted(msg)) {
packetsLost++;
}
}
send(msg, “out”);
}
}
bool isRerouted(cMessage *msg) {
// Logic to determine if the packet has been rerouted
return msg->getArrivalGate()->getIndex() == 2; // Example: rerouted to node 2
}
virtual void finish() override {
EV << “Packets sent: ” << packetsSent << endl;
EV << “Packets received: ” << packetsReceived << endl;
EV << “Packets lost during failover: ” << packetsLost << endl;
recordScalar(“Packets Lost During Failover”, packetsLost);
}
};
- Post-Simulation Analysis
Use OMNeT++’s built-in tools to examine the recorded metrics after running the simulation. This will offer insights into how successfully the network handles failover events, with the speed of failover, the amount of packet loss, and the impact on overall network performance.
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