How to Calculate Network Delay Variance in NS2

To calculate the Network Delay Variance using NS2 (Network Simulator 2) that frequently referred to as jitter that is the variation in packet delays across the time. This is vital metric in the real-time applications like video conferencing, VoIP, and online gaming that consistent packet delivery is essential for maintaining the quality of service (QoS). It is estimated by calculating the variances among the delays of consecutive packets and ascertaining how much these delays are diverge from the average delay. We provide typical steps to estimate the network delay variance within NS2:

Steps to Calculate Network Delay Variance in NS2

To analyse network delay variance (or jitter), we require to:

Capture the transmission and reception times of every packet in the simulation.
Compute the end-to-end delay for each packet (time between transmission and reception).
Evaluate the difference in the delays that is how much the delays are deviate from the average delay.

Formula for Delay Variance:

For each packet iii, the delay variance (jitter) is calculated as:

Jitter=1n∑i=1n(Delayi−Average Delay)2\text{Jitter} = \frac{1}{n} \sum_{i=1}^{n} \left( \text{Delay}_i – \text{Average Delay} \right)^2Jitter=n1i=1∑n(Delayi−Average Delay)2

Where:

nnn is the total number of packets.
Delay is the time variance among the packet reception and packet transmission.
Average Delay is the mean of all end-to-end delays.

Set Up NS2 Simulation:

Initially, we configure a replication in which packets are transferred from a source node to a destination node. The delay variance will assess rely on the transmission and reception times of these packets.

Example TCL Script for Data Transmission:

# Create the simulator

set ns [new Simulator]

# Create 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 instance:

A source node delivers the packets to an end node over a 1 Mbps link with a 10 ms propagation delay.
We will be estimated the trace file to analyse the end-to-end delays and the delay variance (jitter).

Trace File Overview:

The trace file (out.tr) generated by NS2 records the packet transmission and reception events that will use to estimate the delay variance.

Example Trace File Entries:

s 2.000000000 _0_ AGT — 512 cbr 0 0.0 1.0 1.0

r 2.010000000 _1_ AGT — 512 cbr 0 0.0 1.0 1.0

s 3.000000000 _0_ AGT — 512 cbr 1 0.0 2.0 2.0

r 3.015000000 _1_ AGT — 512 cbr 1 0.0 2.0 2.0

Here:

s: Packet sent.
r: Packet received.
0 and 1: Node IDs (source node _0_, destination node _1_).
512: Packet size in bytes.

Calculating End-to-End Delay:

For every packet, the end-to-end delay is computed as:

Delayi=Reception Timei−Transmission Timei\text{Delay}_i = \text{Reception Time}_i – \text{Transmission Time}_iDelayi=Reception Timei−Transmission Timei

When we have the delays for each packet then we can be calculated the average delay also then estimate the variance in delays to ascertain the jitter.

AWK Script to Calculate Delay Variance:

Step 1: Calculate the Average Delay

Initially, we compute the average delay for all packets.

BEGIN {

total_delay = 0;

received_packets = 0;

}

# Store the time each packet was sent

$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

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

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

total_delay += delay;

delays[received_packets] = delay; # Store the delay for variance calculation

received_packets++;

}

END {

avg_delay = total_delay / received_packets;

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

}

Step 2: Calculate the Delay Variance (Jitter)

When we have the average delay then we can be assessed the variance in the delays (jitter).

BEGIN {

total_delay = 0;

received_packets = 0;

variance = 0;

}

# Store the time each packet was sent

$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

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

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

total_delay += delay;

delays[received_packets] = delay; # Store the delay for variance calculation

received_packets++;

}

END {

# Calculate average delay

avg_delay = total_delay / received_packets;

# Calculate variance (jitter)

for (i = 0; i < received_packets; i++) {

variance += (delays[i] – avg_delay) ^ 2;

}

jitter = variance / received_packets;

print “Delay Variance (Jitter): ” jitter ” seconds^2″;

}

Running the AWK Script:

We can be saved the AWK script as jitter.awk then we run it on the trace file generated by NS2:

awk -f jitter.awk out.tr

Interpreting the Results:

The script will result the average end-to-end delay and the delay variance (jitter).

Example output:

Average End-to-End Delay: 0.012 seconds

Delay Variance (Jitter): 0.000015 seconds^2

The average end-to-end delay denotes the usual delay experienced by packets within the network.
The delay variance (jitter) measures how much the delays are differ from the average delay. A lower variance shows more consistent delays, whereas a higher variance shows more fluctuation in delay times.

Conclusion:

To estimate the network delay variance (jitter) in NS2:

Configure the simulation and generate a trace file including packet transmission and reception events.
Estimate the trace file using AWK scripts to compute the end-to-end delay for each packet.
Assess the delay variance (jitter) by comparing the delays to the average delay.
The outcomes is calculate of the variation in packet delays that is vital for computing the performance of real-time and time-sensitive applications.

In this setup, we shown the calculation methods on how to compute the Network Delay Variance using some examples within NS2 simulation platform. If you require further details on this topic then we will be delivered. Provide us with all the parameter details, and we guarantee you the best comparison project outcomes. Calculating Network Delay Variance in NS2 can be quite challenging, so keep in contact with us, and we will assist you in achieving the best results.