How to Calculate Network Latency in NS2

To calculate network latency in ns2 has needs to define the end-to-end delay or round-trip time (RTT) knowledgeable by packets as they go from a source node to a destination node. Latency is key parameters in networks and it is specifically significant for applications that need a real-time data, like voice over IP (VoIP), video streaming, or online gaming. The below is the approach to calculate the network latency in ns2:

We can compute network latency using the following parameters:

End-to-End Delay: The time it proceeds for a packet to transportable from the source to the destination.
Round-Trip Time (RTT): The time it takes for a packet to go from the source to the destination and back.

Steps to Calculate Network Latency in NS2

Set Up NS2 Simulation:

To estimate network latency, we will replicate a scenario in which packets are sent from one node (source) to another node (destination). we will then measure the trace file to estimate the delay or latency.

Example TCL Script for Data Transmission:

# Create the simulator

set ns [new Simulator]

# Define the topology with two nodes: source and destination

set node_(0) [$ns node]

set node_(1) [$ns node]

# Create a duplex link between the nodes (1 Mbps bandwidth, 10ms delay)

$ns duplex-link $node_(0) $node_(1) 1Mb 10ms DropTail

# Attach UDP agents to nodes for sending and receiving data

set udp0 [new Agent/UDP]

set sink [new Agent/Null]

$ns attach-agent $node_(0) $udp0

$ns attach-agent $node_(1) $sink

$ns connect $udp0 $sink

# Set up CBR traffic on the UDP agent

set cbr0 [new Application/Traffic/CBR]

$cbr0 attach-agent $udp0

$cbr0 set packetSize_ 512 ;# Packet size in bytes

$cbr0 set rate_ 1Mb ;# Transmission rate

# Start and stop the traffic

$ns at 1.0 “$cbr0 start”

$ns at 10.0 “$cbr0 stop”

# Enable tracing to capture packet transmission and reception

set tracefile [open out.tr w]

$ns trace-all $tracefile

# End the simulation after 12 seconds

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# End simulation at 12 seconds

$ns at 12.0 “finish”

In this simulation:

The source node sends packets to the destination node over a link with 1 Mbps bandwidth and 10 ms propagation delay.
We can estimate latency by calculating the time among packet transmission and reception.

Trace File Overview:

After executing the simulation, NS2 creates a trace file (out.tr) that logs events like packet transmission, reception, and drop. We will utilize this trace file to estimate the end-to-end delay for packets.

Example Trace File Entries:

s 1.000000000 _0_ AGT — 512 cbr 0 0.0 1.0 1.0

r 1.010000000 _1_ AGT — 512 cbr 0 0.0 1.0 1.0

s 2.000000000 _0_ AGT — 512 cbr 1 0.0 2.0 2.0

r 2.010000000 _1_ AGT — 512 cbr 1 0.0 2.0 2.0

In this example:

s: Packet sent event.
r: Packet received event.
0 and 1: Node IDs (source node _0_ and destination node _1_).
512: Packet size in bytes.
1.000000000: Time when the packet was sent.
1.010000000: Time when the packet was received.

Calculate End-to-End Latency:

The end-to-end delay for a packet can be estimated as the difference among the time a packet is sent and the time it is received at the destination node.

End-to-End Delayi=Reception Timei−Transmission Timei\text{End-to-End Delay}_i = \text{Reception Time}_i – \text{Transmission Time}_iEnd-to-End Delayi=Reception Timei−Transmission Timei

AWK Script to Calculate Average End-to-End Latency:

We can utilize the following AWK script to estimate the average latency by calculating the end-to-end delay for each packet and averaging the values.

AWK Script:

BEGIN {

total_delay = 0;

received_packets = 0;

}

# Record the time each packet was sent from the source node (_0_)

$1 == “s” && $4 == “_0_” && $7 == “cbr” {

packet_time[$10] = $2; # Store the transmission time indexed by packet ID

}

# Calculate the delay for each received packet at the destination node (_1_)

$1 == “r” && $4 == “_1_” && $7 == “cbr” {

delay = $2 – packet_time[$10]; # Calculate the end-to-end delay

total_delay += delay;

received_packets++;

}

END {

if (received_packets > 0) {

avg_delay = total_delay / received_packets;

print “Average End-to-End Delay (Latency): ” avg_delay ” seconds”;

} else {

print “No packets received!”;

}

This script:

Tracks the time each packet is sent from the source node and received at the destination node.
Calculate the end-to-end delay for each packet and then estimate the average latency.

Running the AWK Script:

Save the AWK script as latency.awk, and executed it on the trace file created by NS2:

awk -f latency.awk out.tr

Calculate Round-Trip Time (RTT):

If we are interested in Round-Trip Time (RTT), that is the time it proceeds for a packet to travel from the source to the destination and back, we can mimic this by allowing bidirectional communication. evaluate the time it takes for an acknowledgment to return to the sender after sending a request.

AWK Script for RTT:

BEGIN {

request_sent_time = 0;

response_received_time = 0;

total_rtt = 0;

rtt_count = 0;

}

# Record the time the request is sent from the client (source)

$1 == “s” && $4 == “_0_” && $7 == “cbr” {

request_sent_time = $2;

}

# Record the time the response (acknowledgment) is received at the client (source)

$1 == “r” && $4 == “_0_” && $7 == “cbr” {

response_received_time = $2;

if (request_sent_time > 0) {

rtt = response_received_time – request_sent_time;

total_rtt += rtt;

rtt_count++;

}

END {

if (rtt_count > 0) {

avg_rtt = total_rtt / rtt_count;

print “Average Round-Trip Time (RTT): ” avg_rtt ” seconds”;

} else {

print “No response received!”;

}

Running the AWK Script for RTT:

Save this script as rtt.awk and executed it on the trace file:

awk -f rtt.awk out.tr

Conclusion:

To compute network latency (end-to-end delay) or Round-Trip Time (RTT) in NS2:

Set up the simulation with packets being sent from a source to a destination.
Enable tracing to capture the transmission and reception events.
Analyse the trace file using AWK scripts to estimate whether the end-to-end delay or RTT.
The outcome will provide you the average latency that is need for measuring the performance of delay-sensitive applications like real-time streaming, VoIP, and gaming.

We clearly learned and demonstrate how to calculate and measure the network latency using the ns2 tool with sample code snippets and we also offer the more additional data regarding the network latency. Please provide us with all relevant parameter details, and we guarantee optimal comparison outcomes. For any project ideas or topics, do not hesitate to reach out to us. Calculating network latency in NS2 can be quite challenging; therefore, we encourage you to stay connected with us for expert guidance and superior results.