How to Calculate Maximum Deadline in Ns3

To calculate the maximum deadline in ns3, we had to simulate a scenario in which the packets or tasks meet the deadlines and also to evaluates the maximum delay observed. This is mainly used in real-time systems in that tasks or packets are processed or delivered in a specific time frame.

The following steps will provide the instructions to simulate the tasks or packets with deadlines, and calculate the maximum deadline observed during the simulation.

Steps to Calculate Maximum Deadline in ns3

1. Set Up ns3 Environment:
   • Make sure ns3 is installed on the system.
2. Create a New ns-3 Script:
   • Create a new script file in the scratch directory of ns-3, e.g., deadline_calculation.cc.
3. Include Necessary Headers:
   • Include the necessary ns-3 headers in your script.
4. Define Network Topology:
   • Set up a network topology with multiple nodes.
5. Simulate Tasks or Packets with Deadlines:
   • Implement logic to simulate tasks or packets with deadlines.
6. Measure Delays and Calculate Maximum Deadline:
   • Use ns-3 tracing or callbacks to measure the delay of each packet or task and then determine the maximum delay observed.

Example Code:

Here we hqad provide the simplifies example to simulate tasks or packets with deadlines and calculate the maximum deadlines in ns3 by using the UDP packets to measure the delay.

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/point-to-point-module.h”

#include “ns3/applications-module.h”

#include “ns3/packet-sink.h”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“DeadlineCalculationExample”);

double maxDelay = 0.0;

void PacketReceiveCallback(Ptr<Socket> socket)

{

Ptr<Packet> packet;

Address from;

while ((packet = socket->RecvFrom(from)))

{

Time sendTime;

packet->PeekPacketTag(sendTime);

Time delay = Simulator::Now() – sendTime;

if (delay.GetSeconds() > maxDelay)

{

maxDelay = delay.GetSeconds();

}

std::cout << “Packet received with delay: ” << delay.GetSeconds() << ” seconds” << std::endl;

}

}

void GenerateTraffic(Ptr<Socket> socket, uint32_t pktSize, uint32_t pktCount, Time interPacketInterval)

{

if (pktCount > 0)

{

Ptr<Packet> packet = Create<Packet>(pktSize);

packet->AddPacketTag(Simulator::Now());

socket->Send(packet);

Simulator::Schedule(interPacketInterval, &GenerateTraffic, socket, pktSize, pktCount – 1, interPacketInterval);

}

}

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

{

uint32_t nNodes = 2;

double simulationTime = 10.0; // seconds

uint32_t packetSize = 1024; // bytes

uint32_t numPackets = 100;

double interPacketInterval = 0.1; // seconds

 

CommandLine cmd;

cmd.AddValue(“nNodes”, “Number of nodes”, nNodes);

cmd.AddValue(“simulationTime”, “Total simulation time”, simulationTime);

cmd.AddValue(“packetSize”, “Size of each packet”, packetSize);

cmd.AddValue(“numPackets”, “Number of packets to send”, numPackets);

cmd.AddValue(“interPacketInterval”, “Interval between packets”, interPacketInterval);

cmd.Parse(argc, argv);

NodeContainer nodes;

nodes.Create(nNodes);

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute(“DataRate”, StringValue(“5Mbps”));

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

NetDeviceContainer devices;

devices = pointToPoint.Install(nodes);

InternetStackHelper stack;

stack.Install(nodes);

Ipv4AddressHelper address;

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

Ipv4InterfaceContainer interfaces = address.Assign(devices);

 

Ptr<Socket>recvSocket=Socket::CreateSocket(nodes.Get(1), TypeId::LookupByName(“ns3::UdpSocketFactory”));

InetSocketAddress local = InetSocketAddress(Ipv4Address::GetAny(), 9);

recvSocket->Bind(local);

recvSocket->SetRecvCallback(MakeCallback(&PacketReceiveCallback));

Ptr<Socket>sourceSocket=Socket::CreateSocket(nodes.Get(0), TypeId::LookupByName(“ns3::UdpSocketFactory”));

InetSocketAddress remote = InetSocketAddress(interfaces.GetAddress(1), 9);

sourceSocket->Connect(remote);

Simulator::ScheduleWithContext(sourceSocket->GetNode()->GetId(), Seconds(1.0), &GenerateTraffic, sourceSocket, packetSize, numPackets, Seconds(interPacketInterval));

Simulator::Stop(Seconds(simulationTime));

Simulator::Run();

Simulator::Destroy();

std::cout << “Maximum delay observed: ” << maxDelay << ” seconds” << std::endl;

return 0;

}

Explanation:

1. Nodes and Links:
   • Created two nodes and configured a point-to-point network between them.
   • Set up the network with nodes connected using point-to-point links.
2. Applications:
   • Created a UDP socket on the receiver node and set a callback function PacketReceiveCallback to handle received packets.
   • Created a UDP socket on the sender node to send packets.
3. Traffic Generation:
   • Implemented the GenerateTraffic function to send packets from the source node to the sink node at regular intervals.
   • Each packet is tagged with the current simulation time to track when it was sent.
4. Delay Measurement:
   • Implemented the PacketReceiveCallback function to calculate the delay of each received packet by comparing the current simulation time with the timestamp in the packet tag.
   • Updated the maxDelay variable if the current packet’s delay is greater than the previously observed maximum delay.
5. Running the Simulation:
   • The simulation runs, sending and receiving packets.
   • After the simulation, the maximum delay observed is printed.

At last, the calculation of maximum deadline in ns3 is done successfully by measuring the delays and calculating the maximum deadline using UDP packets.

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