How to implement switching protocols in OMNeT++
To implement switching protocols in OMNeT++ has numerous steps. The Switching protocols, like Spanning Tree Protocol (STP) or Rapid Spanning Tree Protocol (RSTP), are vital for handling the network switches and guarantee a loop-free topology. Below is the structure to implement the switching protocol in OMNeT++:
Step-by-Step Implementation:
Step 1: Set Up OMNeT++ and INET Framework
- Install OMNeT++: Download and install the latest version of OMNeT++ from the OMNeT++
- Install INET Framework: Download and install the INET framework from the INET repository.
Step 2: Understand Switching Protocols
The Switching protocols such as STP/RSTP are mitigating the network loops by generating a spanning tree inside a network of connected layer-2 bridges (switches). The protocols use Bridge Protocol Data Units (BPDUs) to transmission among switches.
Step 3: Create the Switching Protocol Module
Define the Module in .ned File
Create a .ned file for the switching protocol module.
ned
Copy code
simple STP
{
parameters:
double helloTime @unit(s) = default(2s); // Interval for sending BPDUs
double maxAge @unit(s) = default(20s); // Maximum age of BPDU information
double forwardDelay @unit(s) = default(15s); // Forward delay timer
gates:
input fromNetworkLayer[];
output toNetworkLayer[];
}
Implement the Module in C++
Create the corresponding .cc and .h files.
STP.h
#ifndef __STP_H_
#define __STP_H_
#include <omnetpp.h>
#include “inet/networklayer/contract/IRoutingTable.h”
#include “inet/networklayer/common/L3AddressResolver.h”
#include “inet/networklayer/ipv4/IPv4Datagram.h”
#include <map>
using namespace omnetpp;
using namespace inet;
class STP : public cSimpleModule
{
private:
double helloTime;
double maxAge;
double forwardDelay;
cMessage *helloMsg;
IRoutingTable *routingTable;
std::map<int, simtime_t> bpduAge; // Age of received BPDUs
protected:
virtual void initialize() override;
virtual void handleMessage(cMessage *msg) override;
void sendBPDU();
void processBPDU(cMessage *msg);
public:
STP();
virtual ~STP();
};
#endif
STP.cc
#include “STP.h”
Define_Module(STP);
STP::STP()
{
helloMsg = nullptr;
}
STP::~STP()
{
cancelAndDelete(helloMsg);
}
void STP::initialize()
{
helloTime = par(“helloTime”);
maxAge = par(“maxAge”);
forwardDelay = par(“forwardDelay”);
helloMsg = new cMessage(“sendHello”);
routingTable = getModuleFromPar<IRoutingTable>(par(“routingTableModule”), this);
scheduleAt(simTime() + helloTime, helloMsg);
}
void STP::handleMessage(cMessage *msg)
{
if (msg == helloMsg)
{
sendBPDU();
scheduleAt(simTime() + helloTime, helloMsg);
}
else if (strcmp(msg->getName(), “BPDU”) == 0)
{
processBPDU(msg);
}
else
{
// Handle other messages
}
}
void STP::sendBPDU()
{
cMessage *bpdu = new cMessage(“BPDU”);
for (int i = 0; i < gateSize(“toNetworkLayer”); ++i)
{
send(bpdu->dup(), “toNetworkLayer”, i);
}
delete bpdu;
}
void STP::processBPDU(cMessage *msg)
{
// Implement processing of BPDU message
int srcGate = msg->getArrivalGate()->getIndex();
bpduAge[srcGate] = simTime();
// Check for outdated BPDUs
for (auto it = bpduAge.begin(); it != bpduAge.end();)
{
if (simTime() – it->second > maxAge)
{
it = bpduAge.erase(it);
}
else
{
++it;
}
}
delete msg;
}
Step 4: Integrate with Simulation Model
Incorporate the STP module into a network simulation model.
Network Configuration .ned File
network STPNetwork
{
submodules:
switch1: StandardHost {
parameters:
@display(“p=100,100”);
routingTableModule = “^.routingTable”;
}
switch2: StandardHost {
parameters:
@display(“p=300,100”);
routingTableModule = “^.routingTable”;
}
// Add more switches as needed
connections:
switch1.pppg++ <–> { @display(“m=100,100”); } <–> switch2.pppg++;
}
omnetpp.ini Configuration
network = STPNetwork
*.switch*.pppg[*].queue.typename = “DropTailQueue”
*.switch*.ipv4.routingTable = “inet.networklayer.routing.manet.Router”
*.switch*.networkLayer.networkProtocol.typename = “IPv4NetworkLayer”
*.switch*.transportLayer.tcp.typename = “Tcp”
*.switch*.transportLayer.udp.typename = “Udp”
*.switch*.application[*].typename = “UdpBasicApp”
*.switch*.application[*].destAddresses = “switch1” // Set destination as needed
*.switch*.application[*].destPort = 2000
*.switch*.application[*].startTime = uniform(0s, 10s)
*.switch*.application[*].sendInterval = uniform(1s, 2s)
*.switch*.application[*].packetLength = 512B
*.switch*.app[0].typename = “STP”
Step 5: Test and Debug
- Run Simulations: Implement simulations to investigate the conduct STP module under various network conditions.
- Analyse Results: Verify the correctness and performance of your implementation.
- Debugging: Use OMNeT++’s debugging tools to troubleshoot any issues.
As we discussed earlier about how the switching protocols will perform in OMNeT++ tool and we help to provide further information about how the switching protocols will adapt in diverse scenarios.