How to Begin Implement Mail Transfer Protocol in ns3

To implement a Mail Transfer Protocol in NS3, such as a basic version of SMTP (Simple Mail Transfer Protocol), has been including their build a custom of application which replicates the behavior for forwarding and receiving email communications. Here’s a step-by-step guide:

Steps to Begin Implement Mail Transfer Protocol in ns3

Step 1: Understand the Mail Transfer Protocol

1. SMTP Basics:
   • Purpose: SMTP is used for forwarding the emails among mail servers and from clients to servers.
   • Communication Flow:
     • Client: Transmitting the email request by sender, recipient, and communication data.
     • Server: Recognizes the receipt and manage the delivery.
   • Key Commands: The SMTP concludes the some of commands they are HELO, MAIL FROM, RCPT TO, DATA, and QUIT.
2. Simulation Goals:
   • Clarify the SMTP for replications such as basic email send/receive workflow.
   • Concentrate on the protocol flow rather than full SMTP functionality.

Step 2: Set Up NS-3

1. Install NS-3:

git clone https://gitlab.com/nsnam/ns-3-dev.git

cd ns-3-dev

./ns3 configure –enable-examples –enable-tests

./ns3 build

1. Verify Installation: Run a sample script:

./ns3 run examples/tutorial/first

Step 3: Plan the Mail Transfer Protocol

1. Components:
   • SMTP Client: The client replicates a sending an email.
   • SMTP Server: The server replicates a receiving and treat the email.
   • Message Exchange: Use tool NS3 sockets for transmission.
2. Simplified Workflow:
   • Clients are forward the MAIL FROM, RCPT TO, and DATA.
   • Server responds by 250 OK for successful processes.
   • Client transmit the QUIT for dismiss the session.

Step 4: Implement the Mail Transfer Protocol

Step 4.1: Define the SMTP Server

Create a class for the server application:

#include “ns3/application.h”

#include “ns3/socket.h”

using namespace ns3;

class SmtpServer : public Application {

public:

static TypeId GetTypeId(void);

SmtpServer();

virtual ~SmtpServer();

private:

virtual void StartApplication() override;

virtual void StopApplication() override;

void HandleRequest(Ptr<Socket> socket);

Ptr<Socket> m_socket;

Address m_localAddress;

};

Step 4.2: Define the SMTP Client

Develop a class for the client application:

#include “ns3/application.h”

#include “ns3/socket.h”

using namespace ns3;

class SmtpClient : public Application {

public:

static TypeId GetTypeId(void);

SmtpClient();

virtual ~SmtpClient();

void SetServer(Address serverAddress);

private:

virtual void StartApplication() override;

virtual void StopApplication() override;

void SendEmail();

Ptr<Socket> m_socket;

Address m_serverAddress;

};

Step 4.3: Implement Core Functions

• SMTP Server Logic:
  • Begin and drop the server.
  • It maintains the incoming requests.

void SmtpServer::StartApplication() {

m_socket = Socket::CreateSocket(GetNode(), TypeId::LookupByName(“ns3::TcpSocketFactory”));

InetSocketAddress local = InetSocketAddress(Ipv4Address::GetAny(), 25);

m_socket->Bind(local);

m_socket->Listen();

m_socket->SetAcceptCallback(

MakeNullCallback<bool, Ptr<Socket>, const Address &>(),

MakeCallback(&SmtpServer::HandleRequest, this));

}

void SmtpServer::StopApplication() {

if (m_socket) {

m_socket->Close();

}

}

void SmtpServer::HandleRequest(Ptr<Socket> socket) {

// Read the incoming data and respond

Ptr<Packet> packet = socket->Recv();

std::string data = std::string((char *)packet->PeekData(), packet->GetSize());

std::cout << “Received: ” << data << std::endl;

// Respond with “250 OK”

Ptr<Packet> response = Create<Packet>((uint8_t *)”250 OK”, 6);

socket->Send(response);

}

• SMTP Client Logic:
  • Launch the connection and transmit the email commands.

void SmtpClient::StartApplication() {

m_socket = Socket::CreateSocket(GetNode(), TypeId::LookupByName(“ns3::TcpSocketFactory”));

m_socket->Connect(m_serverAddress);

Simulator::Schedule(Seconds(1.0), &SmtpClient::SendEmail, this);

}

void SmtpClient::StopApplication() {

if (m_socket) {

m_socket->Close();

}

}

void SmtpClient::SendEmail() {

// Send MAIL FROM

Ptr<Packet> mailFrom = Create<Packet>((uint8_t *)”MAIL FROM: sender@example.com”, 27);

m_socket->Send(mailFrom);

// Send RCPT TO

Ptr<Packet> rcptTo = Create<Packet>((uint8_t *)”RCPT TO: recipient@example.com”, 29);

m_socket->Send(rcptTo);

// Send DATA

Ptr<Packet> data = Create<Packet>((uint8_t *)”DATA\nHello World!\n.\n”, 21);

m_socket->Send(data);

// Send QUIT

Ptr<Packet> quit = Create<Packet>((uint8_t *)”QUIT”, 4);

m_socket->Send(quit);

}

Step 5: Set Up the Simulation

Express a network topology and install the SMTP applications:

int main(int argc, char *argv[]) {

NodeContainer nodes;

nodes.Create(2);

PointToPointHelper p2p;

p2p.SetDeviceAttribute(“DataRate”, StringValue(“10Mbps”));

p2p.SetChannelAttribute(“Delay”, StringValue(“2ms”));

NetDeviceContainer devices = p2p.Install(nodes);

InternetStackHelper stack;

stack.Install(nodes);

Ipv4AddressHelper address;

address.SetBase(“10.1.1.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces = address.Assign(devices);

// Set up the SMTP Server

Ptr<SmtpServer> server = CreateObject<SmtpServer>();

nodes.Get(1)->AddApplication(server);

server->SetStartTime(Seconds(1.0));

server->SetStopTime(Seconds(10.0));

// Set up the SMTP Client

Ptr<SmtpClient> client = CreateObject<SmtpClient>();

client->SetServer(InetSocketAddress(interfaces.GetAddress(1), 25));

nodes.Get(0)->AddApplication(client);

client->SetStartTime(Seconds(2.0));

client->SetStopTime(Seconds(10.0));

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 6: Test and Debug

1. Enable Logging:
   • Use the metrices for debug tool NS-3:

export NS_LOG=”SmtpServer=level_all|prefix_time,SmtpClient=level_all|prefix_time”

./ns3 run my-simulation

1. Validate Behavior:
   • Verify the commands for client sends correctly.
   • Validate the server responses for instance “250 OK”.

Step 7: Extend and Optimize

1. Enhancements:
   • Improve helps for several recipients.
   • Execute the more SMTP commands for sample HELO, AUTH.
2. Performance Testing:
   • It replicates the many clients and servers.
   • Study the performance of using the testing like as FlowMonitor.

In the end of the simulation, we all learn and get knowledge about the Simple Mail Transfer Protocol that is used for communication through email was simulated in ns3 simulation tool. We will elaborate on the Simple Mail Transfer Protocol strategy applied in different simulation instances in further manual.