How to Calculate End to End Delay in ns3

Calculating end-to-end delay in ns3 involves measuring the time taken for a packet to traverse from the source to the destination. End-to-end delay can be calculated by subtracting the send time of the packet from its receive time. Below is the guide on calculating end-to-end delay in ns3.

Steps for calculating end-to-end delay

1. Set up the simulation :

• To simulate the network, create a network topology with nodes, protocols and links configured.

2. Install applications :

• To generate and receive traffic, set up application.

3. Trace the packets :

• To record the send and receive times of packets, use ns3 tracing capabilities.

4. Calculate end-to-end delay :
   • Subtract the send time from the receive time for each packet.

Below is an example to demonstrate the process:

1. set up the simulation

Create a simple network topology by using a point-to-point link between two nodes.

#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”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“EndToEndDelayExample”);

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

{

// Create two nodes

NodeContainer nodes;

nodes.Create (2);

// Set up the point-to-point link

PointToPointHelper pointToPoint;

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

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

// Install the link devices on the nodes

NetDeviceContainer devices;

devices = pointToPoint.Install (nodes);

// Install the internet stack

InternetStackHelper stack;

stack.Install (nodes);

// Assign IP addresses

Ipv4AddressHelper address;

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

Ipv4InterfaceContainer interfaces = address.Assign (devices);

// Set up the UDP echo server and client

uint16_t port = 9; // well-known echo port number

UdpEchoServerHelper echoServer (port);

ApplicationContainer serverApps = echoServer.Install (nodes.Get (1));

serverApps.Start (Seconds (1.0));

serverApps.Stop (Seconds (10.0));

UdpEchoClientHelper echoClient (interfaces.GetAddress (1), port);

echoClient.SetAttribute (“MaxPackets”, UintegerValue (100));

echoClient.SetAttribute (“Interval”, TimeValue (Seconds (0.1))); // 10 packets per second

echoClient.SetAttribute (“PacketSize”, UintegerValue (1024));

ApplicationContainer clientApps = echoClient.Install (nodes.Get (0));

clientApps.Start (Seconds (2.0));

clientApps.Stop (Seconds (10.0));

// Enable tracing

AsciiTraceHelper ascii;

pointToPoint.EnableAsciiAll (ascii.CreateFileStream (“end-to-end-delay.tr”));

// Run the simulation

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

2. Install applications

In the above example, on one node a UDP echo server is installed. and on another node, a UDP echo client is installed. The client sends 1000 packets, each 1024 bytes in size, at an interval of 0.01 seconds.

3. Trace the packets

There are several ways to trace packets in ns3. We can use either ASCII or PCAP tracing. But in our example, we enabled ASCII tracing.

4. Calculate end-to-end delay

Parse the trace file to extract the send and receive times of packets after the simulation. Here is a basic way to process the trace file :

Example Python Script to Calculate end-to-end delay

send_times = {}

recv_times = {}

with open(“end-to-end-delay.tr”, “r”) as trace_file:

for line in trace_file:

fields = line.split()

time = float(fields[1])  # Assuming the time is the second field

node_id = fields[2]

event = fields[3]

packet_id = fields[5]  # Assuming packet ID is the sixth field

if “UdpEchoClient” in line and “Sent” in event:

send_times[packet_id] = time

elif “UdpEchoServer” in line and “Received” in event:

recv_times[packet_id] = time

delays = []

for packet_id in send_times:

if packet_id in recv_times:

delays.append(recv_times[packet_id] – send_times[packet_id])

average_delay = sum(delays) / len(delays) if delays else 0

print(f”Average End-to-End Delay: {average_delay} seconds”)

Explanation

1. Simulation setup :

Two nodes are created. Those nodes are connected using a point-to-point link.

2. Application setup :

On one node, a UDP echo server is installed. and On another node, a UDP echo client is installed. Configure the client to send a specified number of packets at a specified interval.

3. Packet tracing :

To record packet events, enable ASCII.

4. Calculating end-to-end delay :

to extract the send and receive times of packets, parse the trace files. Subtract the send time from the receive time for each packet to get the end-to-end delay.

Overall, we went through the guide on calculating end-to-end delay in ns3 by measuring the time taken for a packet to travel from the source to the destination. Also, we offer more topics related to end-to-end delay.

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