How to Implement Network Flexible Branching in NS2

To implement the Network Flexible Branching in Network simulator 2 (NS2), this branching is a network set up in which various branches (paths) are dynamically modified in terms of network conditions, load or performance metrics. It is commonly applied in networks to enable flexible routing, load balancing or multi-path communication. We can simulate flexible branching by building multiple paths amongst source and destination nodes and dynamically modified traffic routing depends on particular metrics like network load, packet loss or latency.

Below, we provide the step-by-step demonstration on how you can implement this in ns2:

Steps to Implement Network Flexible Branching in NS2:

  1. Set Up the Network Topology

Start by configuring a network topology with numerous paths (branches) exists amongst the source and destination. It will permit you to replicate flexible branching by dynamically altering traffic over various paths.

Example TCL Script for Basic Setup:

# Create a simulator instance

set ns [new Simulator]

# Define link parameters (bandwidth and delay)

set bw 10Mb          ;# Bandwidth for each link

set delay 10ms       ;# Delay for each link

# Create network nodes

set node1 [$ns node]   ;# Source node

set node2 [$ns node]   ;# Intermediate node (Branch 1)

set node3 [$ns node]   ;# Intermediate node (Branch 2)

set node4 [$ns node]   ;# Intermediate node (Branch 3)

set node5 [$ns node]   ;# Destination node

# Create links between the nodes

$ns duplex-link $node1 $node2 $bw $delay DropTail   ;# Path 1 (via node2)

$ns duplex-link $node2 $node5 $bw $delay DropTail

$ns duplex-link $node1 $node3 $bw $delay DropTail   ;# Path 2 (via node3)

$ns duplex-link $node3 $node5 $bw $delay DropTail

$ns duplex-link $node1 $node4 $bw $delay DropTail   ;# Path 3 (via node4)

$ns duplex-link $node4 $node5 $bw $delay DropTail

This topology builds three branches (paths) amongst Node1 (source) and Node5 (destination):

  • Path 1: Via Node2
  • Path 2: Via Node3
  • Path 3: Via Node4
  1. Configure Traffic for Each Path

Secondly, set up traffic for all paths. We can imitate traffic branching and dynamic routing by generating traffic flows. You can also modify the traffic dynamically during the simulation depends on network conditions.

Example of Configuring Traffic:

# Create a UDP agent for traffic from Node1 (source)

set udp_src [new Agent/UDP]

$ns attach-agent $node1 $udp_src

# Create a CBR traffic generator to simulate constant packet flow

set cbr_src [new Application/Traffic/CBR]

$cbr_src set packet_size_ 500      ;# Packet size in bytes

$cbr_src set rate_ 2Mb             ;# Data rate (e.g., 2 Mbps)

$cbr_src attach-agent $udp_src

# Create a UDP sink at Node5 (destination)

set null_sink [new Agent/Null]

$ns attach-agent $node5 $null_sink

# Connect source to destination through multiple paths

$ns connect $udp_src $null_sink

# Start and stop the traffic

$ns at 1.0 “$cbr_src start”

$ns at 10.0 “$cbr_src stop”

Here, UDP traffic is created at Node1 and sent to Node5. The traffic flows can be dynamically modified to use numerous paths according to their network conditions.

  1. Simulate Flexible Branching (Dynamic Path Selection)

Depends on the network’s performance metrics includes queue size, packet loss or delay, we have to modify the routes dynamically to implement the flexible branching in the network. Adjust the routing tables dynamically during the simulation by using rtmodel command.

Example: Dynamically Switching Traffic to Another Path

You can replicate the dynamic adjustment of traffic amongst branches by disabling a path and shifting traffic to another path. For instance, you can replicate the failure of Path 1 and switch traffic to Path 2.

# At time 5.0, simulate the failure of Path 1 (via node2)

$ns at 5.0 “$ns rtmodel-at 5.0 down $node1 $node2”

$ns at 5.0 “$ns rtmodel-at 5.0 down $node2 $node5”

# At time 6.0, reroute traffic to Path 2 (via node3)

$ns at 6.0 “$ns rtmodel-at 6.0 up $node1 $node3”

$ns at 6.0 “$ns rtmodel-at 6.0 up $node3 $node5”

This script disables Path 1 at time 5.0 seconds and switches traffic to Path 2 at time 6.0 seconds. This simulates dynamic path switching (flexible branching) in reply to network changes.

  1. Simulate Load Balancing Across Multiple Paths

In addition to switching traffic amongst paths, you can also simulate load balancing by severe the traffic across several paths in terms of network load or performance metrics. This can be accomplished by producing multiple traffic generators and allocating them to various paths.

Example of Load Balancing Traffic:

# Create additional UDP agents for load balancing across multiple paths

# Agent for Path 1 (via node2)

set udp_path1 [new Agent/UDP]

$ns attach-agent $node1 $udp_path1

set cbr_path1 [new Application/Traffic/CBR]

$cbr_path1 set packet_size_ 500

$cbr_path1 set rate_ 1Mb    ;# Assign 1 Mbps to Path 1

$cbr_path1 attach-agent $udp_path1

# Agent for Path 2 (via node3)

set udp_path2 [new Agent/UDP]

$ns attach-agent $node1 $udp_path2

set cbr_path2 [new Application/Traffic/CBR]

$cbr_path2 set packet_size_ 500

$cbr_path2 set rate_ 1Mb    ;# Assign 1 Mbps to Path 2

$cbr_path2 attach-agent $udp_path2

# Create UDP sinks for each path at Node5

set null_sink1 [new Agent/Null]

$ns attach-agent $node5 $null_sink1

$ns connect $udp_path1 $null_sink1

set null_sink2 [new Agent/Null]

$ns attach-agent $node5 $null_sink2

$ns connect $udp_path2 $null_sink2

# Start and stop the traffic for load balancing

$ns at 1.0 “$cbr_path1 start”

$ns at 1.0 “$cbr_path2 start”

$ns at 10.0 “$cbr_path1 stop”

$ns at 10.0 “$cbr_path2 stop”

In this configuration, traffic is split amongst Path 1 and Path 2, with each path carrying 1 Mbps of traffic. This simulates load balancing across several branches in the network.

  1. Enable Tracing and Monitor Path Changes

NS2 offered tracing potential that permit you to observe how packets are transmitted through the network, which paths they take, and how flexible branching impacts the overall traffic distribution.

Enable Trace Files:

# Enable tracing for the simulation

set tracefile [open “flexible_branching_trace.tr” w]

$ns trace-all $tracefile

# Define a finish procedure to end the simulation and close the trace file

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# Set the simulation end time

$ns at 20.0 “finish”

The trace file will capture events like packet transmissions, path changes, and packet drops, granting you to evaluate the network’s flexible branching activities.

  1. Run the Simulation

Finally, execute the simulation to monitor how the network manages flexible branching, load balancing, and dynamic path switching.

# Run the simulation

$ns run

Example Complete TCL Script for Network Flexible Branching Simulation

# Create a simulator instance

set ns [new Simulator]

# Define link parameters (bandwidth and delay)

set bw 10Mb

set delay 10ms

# Create network nodes

set node1 [$ns node]   ;# Source node

set node2 [$ns node]   ;# Intermediate node (Branch 1)

set node3 [$ns node]   ;# Intermediate node (Branch 2)

set node4 [$ns node]   ;# Intermediate node (Branch 3)

set node5 [$ns node]   ;# Destination node

# Create links between the nodes

$ns duplex-link $node1 $node2 $bw $delay DropTail   ;# Path 1 (via node2)

$ns duplex-link $node2 $node5 $bw $delay DropTail

$ns duplex-link $node1 $node3 $bw $delay DropTail   ;# Path 2 (via node3)

$ns duplex-link $node3 $node5 $bw $delay DropTail

$ns duplex-link $node1 $node4 $bw $delay DropTail   ;# Path 3 (via node4)

$ns duplex-link $node4 $node5 $bw $delay DropTail

# Create UDP agent for traffic from Node1 (source) to Node5 (destination)

set udp_src [new Agent/UDP]

$ns attach-agent $node1 $udp_src

# Create CBR traffic generator for UDP source

set cbr_src [new Application/Traffic/CBR]

$cbr_src set packet_size_ 500

$cbr_src set rate_ 2Mb

$cbr_src attach-agent $udp_src

# Create UDP sink at Node5 (destination)

set null_sink [new Agent/Null]

$ns attach-agent $node5 $null_sink

# Connect source to destination through multiple paths

$ns connect $udp_src $null_sink

# Start and stop the traffic

$ns at 1.0 “$cbr_src start”

$ns at 10.0 “$cbr_src stop”

# Simulate dynamic path switching

$ns at 5.0 “$ns rtmodel-at 5.0 down $node1 $node2”

$ns at 5.0 “$ns rtmodel-at 5.0 down $node2 $node5”

$ns at 6.0 “$ns rtmodel-at 6.0 up $node1 $node3”

$ns at 6.0 “$ns rtmodel-at 6.0 up $node3 $node5”

# Enable tracing

set tracefile [open “flexible_branching_trace.tr” w]

$ns trace-all $tracefile

# End simulation

$ns at 20.0 “finish”

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# Run the simulation

$ns run

With the given procedure, you can now understand about how you can implement Network Flexible Branching in NS2 by setting up a multi-path network and simulating dynamic traffic distribution according to their network conditions. If you need any additional information, we will offer them. You can rely on our team for a successful implementation of  Network Flexible Branching in Network simulator 2 tailored to your needs. Get network analysis done by our team effectively