How to Start Overlay Topology Projects Using NS2

To create an Overlay Topology in NS2 (Network Simulator 2) has built a virtual network such as overlay on top of the existing physical network. Overlay networks abstract the fundamental organization and offer the structures such as routing, content delivery, or peer-to-peer communication

Here’s how to start your Overlay Topology project in NS2:

Steps to Simulate Overlay Topology in NS2

  1. Understand Overlay Topology
  • Structure:
    • Nodes in the overlay are linked the virtually using logical connection.
    • Logical connection can span many physical connections in the underlying network.
  • Applications:
    • Peer-to-peer (P2P) networks.
    • Content delivery networks (CDNs).
    • Application-level multicast systems.
    • Virtual private networks (VPNs).
  • Key Features:
    • Separation of logical such as overlay and physical like as underlay topologies.
    • The Multi-hop communication has through an overlay paths.
  1. Set Up NS2
  1. Install NS2:

sudo apt-get install ns2

  1. Verify Installation: validate through a simple replication of script:

ns example.tcl

  1. Define Overlay Topology
  • It built a physical network such as underlay.
  • Launch the logical connection among the overlay nodes which plot to the underlay.
  • Route overlay congestion above the physical network.
  1. TCL Script for Overlay Topology

Under is an sample TCL script for replicate the Overlay Topology:

TCL Script Example

# Initialize NS2 Simulator

set ns [new Simulator]

set tracefile [open overlay_topology.tr w]

$ns trace-all $tracefile

# Define physical network (underlay)

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

# Create physical links

$ns duplex-link $n0 $n1 1Mb 10ms DropTail

$ns duplex-link $n1 $n2 1Mb 10ms DropTail

$ns duplex-link $n2 $n3 1Mb 10ms DropTail

# Define overlay nodes (logical links between physical nodes)

set overlay_n0 $n0

set overlay_n1 $n2

set overlay_n2 $n3

# Logical links in overlay topology (overlay_n0 -> overlay_n1 -> overlay_n2)

# Overlay traffic routed over physical links

set tcp0 [new Agent/TCP]

$ns attach-agent $overlay_n0 $tcp0

set sink0 [new Agent/TCPSink]

$ns attach-agent $overlay_n2 $sink0

$ns connect $tcp0 $sink0

# Add traffic generator

set ftp [new Application/FTP]

$ftp attach-agent $tcp0

# Start overlay traffic

$ns at 1.0 “$ftp start”

# End simulation

$ns at 5.0 “finish”

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

$ns run

  1. Key Features to Simulate
  1. Overlay Traffic:
    • Logical communication between overlay nodes.
    • Fundamental physical network by the Multi-hop routing.
  2. Performance Metrics:
    • Throughput: Amount of data delivery among the overlay nodes.
    • Latency: Study the delays are caused through overlay routing.
    • Packet Loss: Estimate the reliability for the overlay network.
  1. Analyze the Trace File
  • For use the trace files (overlay_topology.tr) and study the overlay network performance.
  • Excerpt the detailed parameter metrics:
    • Throughput:

grep “tcp” overlay_topology.tr > throughput.log

    • Dropped Packets:

grep “drop” overlay_topology.tr > dropped_packets.log

  1. Visualize Results

Use the tool for outcomes Gnuplot or other graphing tool:

  1. Throughput Graph:

set title “Overlay Topology Throughput”

plot “throughput.log” using 1:2 with lines title “Throughput”

  1. Latency Graph:
    • Associate the delays among overlay nodes and physical paths.
  1. Extend the Simulation
  2. Dynamic Overlay Links
  • Replicate the dynamic formation or teardown of overlay connection:

$ns at 2.5 “$ns connect-overlay $overlay_n0 $overlay_n2”

$ns at 4.0 “$ns disconnect-overlay $overlay_n0 $overlay_n1”

  1. Overlay Routing Protocols
  • Execute the routing procedures such as DHT (Distributed Hash Table), Chord, or CAN:

proc overlay-routing {src dst packet} {

# Example: Forward through intermediary nodes

set next_hop [overlay-route $src $dst]

forward $packet $next_hop

}

  1. Experiment with Different Traffic Patterns
  • Enhance the concurrent congestion flows among the overlay nodes:

set udp1 [new Agent/UDP]

$ns attach-agent $overlay_n1 $udp1

set null1 [new Agent/Null]

$ns attach-agent $overlay_n0 $null1

$ns connect $udp1 $null1

  1. Simulate Node Failures
  • Validate the overlay resiliency through replicating a node or connection failures:

$ns at 3.0 “$ns reset-links $n1 $n2”

  1. Modify NS2 Core for Advanced Features
  1. Overlay Node Behavior:
    • Execute the custom packet are maintain or routing logic in the recv() techniques.
  2. Dynamic Overlay Formation:
    • It uses the procedures for built and handle the overlay connection according to the parameter metrics such as latency, bandwidth, or node capacity.

Tools and Resources

  • Wireshark: Examine the overlay congestion and fundamental physical paths.
  • Gnuplot: Envision for performance of parameter metrices such as throughput and latency.
  • NS2 Documentation: Reference for encompass the scripts and functionality.

In this setup we had clearly gather information on how to setup the simulation and how to replicate the Overlay Topology using ns2 tool. We will suggest the insights for the execution of the Overlay Topology in various simulation scenarios.