How to Start Application Layer Projects Using NS2

To start an Application Layer project using NS2 which has needs to replicates the application-level protocols behavior like HTTP, FTP, VoIP, DNS, or custom traffic. The application layer manages the end-user processes and concentrates the data exchange among the applications. NS2 environment have support to replicate the behavior of application layer via default traffic generators and it provides tools such as FTP, CBR (Constant Bit Rate), and traffic across TCP/UDP. Below is a sequential method to get started:

Steps to Start Application Layer Projects in NS2

  1. Understand the Scope of the Application Layer

The application layer within networking that addresses:

  • End-to-end interaction among the software applications.
  • Protocols such as HTTP, FTP, DNS, SMTP, VoIP, and so on.
  • Data generation models like constant rate, bursty, or exponential.

Common Application Layer Project Ideas:

  • Replicate the web traffic to utilize HTTP over TCP.
  • File transfer applying the FTP.
  • Real-time traffic such as VoIP with the support of RTP/UDP.
  • Comparison of application-layer protocols.
  • Performance estimation in diverse network scenarios.
  1. Set Up NS2
  1. Install NS2: We can set up NS2 on the system:

sudo apt-get install ns2

  1. Verify Installation: Run:

ns

If the NS2 prompt is opens, the installation is effectively functioning.

  1. Application Layer in NS2: NS2 environment have inherent support for traffic generation tools such as FTP and CBR. Also, we will need to script custom behaviors.
  1. Define Your Project Goals

Focus on the projects objectives of Application layer to simulate:

  • Application protocol performance such as HTTP vs. FTP.
  • Traffic patterns and QoS metrics such as throughput, latency, and packet loss.
  • Behavior of application-layer in network congestion.
  1. Create a Basic Simulation Script

We can make a TCL script for replicating application-layer behavior.

Example TCL Script:

This instance illustrates the FTP over TCP traffic generation.

# Create a new simulator instance

set ns [new Simulator]

# Open trace and NAM files

set tracefile [open app_layer.tr w]

$ns trace-all $tracefile

set namfile [open app_layer.nam w]

$ns namtrace-all $namfile

# Create network nodes

set client [$ns node]

set server [$ns node]

# Create a duplex link with bandwidth and delay

$ns duplex-link $client $server 1Mb 10ms DropTail

# Attach TCP agents for reliable communication

set tcp [new Agent/TCP]

$ns attach-agent $client $tcp

set sink [new Agent/TCPSink]

$ns attach-agent $server $sink

$ns connect $tcp $sink

# Simulate FTP application on top of TCP

set ftp [new Application/FTP]

$ftp attach-agent $tcp

# Start and stop the FTP session

$ns at 0.5 “$ftp start”

$ns at 4.5 “$ftp stop”

# End simulation

$ns at 5.0 “finish”

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam app_layer.nam &

exit 0

}

$ns run

  1. Run the Simulation
  1. We can store the simulation tcl script like app_layer.tcl.
  2. Then execute the simulation using NS2:

ns app_layer.tcl

  1. Envision the outcomes to apply NAM:

nam app_layer.nam

  1. Analyze Application Layer Metrics
  1. Trace File Analysis: Extort key performance parameters from the .tr file for analysis:
    • Throughput: Compute the ratio of effective data transfer.
    • Latency: Measure the duration for data delivery.
    • Packet Loss: Assess the packets that are lost.
  2. Tools for Analysis: Execute the trace files and make performance graphs leveraging AWK, Python, or MATLAB tools.
  1. Experiment with Advanced Scenarios
  1. HTTP Traffic: Replicate the web traffic with HTTP across TCP:

set http [new Application/Traffic/HTTP]

$http attach-agent $tcp

  1. Real-Time Traffic: Mimic VoIP to utilize RTP/UDP in real-time traffic model:

set udp [new Agent/UDP]

$ns attach-agent $client $udp

set null [new Agent/Null]

$ns attach-agent $server $null

$ns connect $udp $null

set rtp [new Application/Traffic/CBR]

$rtp attach-agent $udp

$rtp set packetSize_ 160

$rtp set interval_ 0.02

  1. Congestion Scenarios: We can launch background traffic for replicating the network congestion:

set udp_bg [new Agent/UDP]

$ns attach-agent $client $udp_bg

set null_bg [new Agent/Null]

$ns attach-agent $server $null_bg

$ns connect $udp_bg $null_bg

  1. Traffic Patterns: We should simulate the real-world behavior of traffic model with the help of CBR or exponential traffic generators:

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $tcp

$cbr set packetSize_ 512

$cbr set interval_ 0.01

  1. Extend the Project
  1. Compare Protocols: Replicate FTP, HTTP, and VoIP and then equate its performance in diverse network situations.
  2. QoS Analysis: Focus on the impact of traffic shaping or prioritization at the application-layer traffic for QoS analysis.
  3. Scalability: Integrate several clients and servers for examining the scalability.
  4. Custom Application Protocols: Execute custom application-layer logic for prolonging NS2 source code.
  1. Document Your Findings

This project should contain:

  • Objectives: To attain the simulation goals.
  • Simulation Setup: Network topology and metrics.
  • Results: Performance parameters such as throughput, latency, and packet loss.
  • Insights: Explanations regarding the application-layer protocols performance.
  1. Tools for Advanced Analysis
  1. AWK or Python: Analyze the trace files using these tools for in-depth metrics.
  2. MATLAB: We can make performance graphs and envision the outcomes using MATLAB environment.

Utilizing a step-by-step process in NS2 environment, we have performed the simulation and analysis for Application Layer Projects that contains valuable insights with sample coding. More advanced topics and example projects ideas will be included in the future.