How to Implement Network Event Management in NS2

To implement the Network Event Management using NS2, which contains managing dynamic events like node failures, link failures, traffic changes, or other network disruptions. By replicating these events then handling them within real-time, we can examine how the network responds and calculate the performance of the protocols under changing the conditions. We show to implement the Network Event Management within NS2 that node and link failures, appending new traffic, and displaying the network response.

Steps to Implement Network Event Management in NS2:

  1. Understand the Event Types:
  • Node Failure: Replicate the failure of a node (e.g., because of a crash or battery depletion).
  • Link Failure: Mimic the failure of a communication link among these two nodes.
  • Traffic Events: Launch new traffic sources or stop existing traffic while the simulation.
  • Network Recovery: Replicate the recovery scenarios, like node reactivation or re-establishing a failed link.
  1. Set Up the Basic Network Topology:
  • Make a simple network in which we can handle the events such as link failures or node failures. Given below instances makes a basic network including several links and nodes.

Example OTcl script for network setup:

set ns [new Simulator]

set nf [open out.tr w]

$ns trace-all $nf

set namfile [open out.nam w]

$ns namtrace-all $namfile

# Define nodes

set node0 [$ns node]   ;# Node 0

set node1 [$ns node]   ;# Node 1

set node2 [$ns node]   ;# Node 2

set node3 [$ns node]   ;# Node 3

# Create links between nodes

$ns duplex-link $node0 $node1 1Mb 10ms DropTail

$ns duplex-link $node0 $node2 1Mb 10ms DropTail

$ns duplex-link $node1 $node3 1Mb 10ms DropTail

$ns duplex-link $node2 $node3 1Mb 10ms DropTail

# Define traffic between node0 and node3

set udp [new Agent/UDP]

set null [new Agent/Null]

$ns attach-agent $node0 $udp

$ns attach-agent $node3 $null

$ns connect $udp $null

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$cbr set packetSize_ 512

$cbr set rate_ 1Mb

$ns at 1.0 “$cbr start”

$ns at 5.0 “$cbr stop”

$ns at 10.0 “finish”

proc finish {} {

global ns nf namfile

$ns flush-trace

close $nf

close $namfile

exec nam out.nam &

exit 0

}

$ns run

  • This script makes a basic topology of four nodes including the traffic among the node3 and node0.
  1. Simulate Node Failure Event:
  • A node failure event mimic a scenario in which a node ends the functioning. We can be disabled a node by stopping its transmission and severing its links.

Example OTcl script to simulate a node failure:

# At time 3.0 seconds, simulate node1 failure by detaching its links

$ns at 3.0 “$ns detach-agent $node1”

$ns at 3.0 “$node1 reset”  ;# Simulate node failure

  • The detach-agent command eliminates the node from the network as well as the reset command deactivates it. After it, the node will no longer participate in the network.
  1. Simulate Link Failure Event:
  • A link failure event can replicate by deactivating a link among two nodes. It may denote a physical disconnection or network outage.

Example OTcl script to simulate a link failure:

# At time 3.0 seconds, simulate link failure between node0 and node1

$ns at 3.0 “$ns link $node0 $node1 down”

  • Above command gives down the link among node0 and node1 at the stipulated time, forcing the network to reroute traffic if possible.
  1. Simulate Traffic Change Events:
  • A traffic change event can use to actively launch or end the traffic while the simulation. It is helpful for analysing how the network adjusts to differing the traffic loads.

Example OTcl script to dynamically add new traffic:

# At time 4.0 seconds, start new traffic between node2 and node3

set udp2 [new Agent/UDP]

set null2 [new Agent/Null]

$ns attach-agent $node2 $udp2

$ns attach-agent $node3 $null2

$ns connect $udp2 $null2

set cbr2 [new Application/Traffic/CBR]

$cbr2 attach-agent $udp2

$cbr2 set packetSize_ 512

$cbr2 set rate_ 1Mb

$ns at 4.0 “$cbr2 start”

$ns at 8.0 “$cbr2 stop”

  • This introduces new traffic among the node2 and node3 at 4.0 seconds as well as the traffic ends at 8.0 seconds.
  1. Simulate Network Recovery (Node or Link Re-activation):
  • A network recovery event replicates the reactivation of a failed node or link. We can give a link or node back online and monitor how the network reacts

Example OTcl script to recover a link or node:

# At time 6.0 seconds, bring the link between node0 and node1 back up

$ns at 6.0 “$ns link $node0 $node1 up”

# At time 7.0 seconds, bring node1 back online

$ns at 7.0 “$node1 reset”  ;# Simulate node recovery

  • The above script restarts the link among the node0 and node1 at 6.0 seconds and retrieves node1 at 7.0 seconds.
  1. Handling Event-Based Packet Loss (Optional):
  • We can be mimicked the impacts of link or node failures on the packet loss. Once a node or link goes down then a packets which was in transit are lost.

Example OTcl script to track packet loss:

# At time 3.0 seconds, simulate link failure and track packet loss

$ns at 3.0 “$ns link $node0 $node1 down”

$ns at 3.0 “$udp drop”

  • The above command replicates a packet loss because of the link failure that packets in transit are dropped.
  1. Run the Simulation and Analyze Events:
  • Run the simulation, after configure the network events. The generated trace files will be included data regarding all network activates that containing the link or node failures and traffic changes.
  • To run the simulation:

ns your_script.tcl

  1. Analyze Event-Driven Metrics:
  • We can examined the effect of network events on vital metrics such as throughput, delay, packet loss, and recovery time by analysing the trace files.
  • We can use the AWK scripts to extract specific metrics from the trace file.

Example AWK script to calculate packet loss:

awk ‘

BEGIN { sent_packets = 0; received_packets = 0; }

{

if ($1 == “+” && $4 == “UDP”) sent_packets++;

if ($1 == “r” && $4 == “UDP”) received_packets++;

}

END {

packet_loss = sent_packets – received_packets;

print “Packet Loss:”, packet_loss;

}’ out.tr

  • The above script counts the total number of sent and received packets to establish the packet loss that is helpful when assessing the impacts of link or node failures.
  1. Visualize the Network Events in NAM:
  • We can envision the network events using the NAM (Network Animator) to monitor how the network topology alters over time because of node or link failures and how traffic flows adapt dynamically.
  • To visualize the simulation in NAM:

nam out.nam

  • It will show the network and we can observe how the links and nodes are perform when recoveries or failures happen.

Summary:

To execute Network Event Management within NS2, we:

  1. Configure a simple network topology including a links and nodes.
  2. Replicate the network events like node or link failures using OTcl commands.
  3. Handle traffic changes by dynamically appending or eliminating the traffic flows.
  4. Simulate recovery events, like reactivating nodes or links.
  5. Estimate the trace files to observe the impacts of this on network performance.
  6. View events in NAM to well understand the dynamic performance of the network.

We had shown the detailed step-by-step implementation and brief summary that helps you to understand this concepts for executing and analysing the Network Event Management within NS2 tool. Also we provide further insights based on your needs.

If you need more help with implementing Network Event Management in the NS2 tool, feel free to reach out to ns2project.com for further assistance with your implementation.