How to Calculate Network Blockage probability in NS2

To calculate the network blockage probability in Network Simulator 2 (NS2), we have to analyse how frequently the communication among nodes are interrupted or congested. It can be defined by assessing the packet drops, failed transmissions or unavailability of communication resources (like bandwidth or signal intrusion). It reflects the possibility that a packet will fail to be send because of such issues.

The below contains the computational steps for the calculation of blockage probability in ns2:

Steps to Calculate Network Blockage Probability:

  1. Set Up the Simulation: Build a simulation with several nodes can interact over a network. You can replicate wireless environments or wired topologies where blockages could happen because of congestion, packet loss, or intervention.
  2. Generate a Trace File: Allow tracing in NS2 to capture detailed packet transmission events as well as packet drops and failed transmissions.
  3. Calculate Blockage Probability: Blockage probability can be stated as the ratio of the amount of blocked (or dropped) packets to the total number of packets sent. This can be estimated using the below formula:

Blockage Probability=Number of Blocked or Dropped PacketsTotal Packets Sent\text{Blockage Probability} = \frac{\text{Number of Blocked or Dropped Packets}}{\text{Total Packets Sent}}Blockage Probability=Total Packets SentNumber of Blocked or Dropped Packets​

Example Tcl Script for NS2 Simulation:

Here’s a sample script to mimic communication amongst nodes and log packet transmission, reception, and drop events.

# Create a new simulator instance

set ns [new Simulator]

# Open trace file to record events

set tracefile [open trace.tr w]

$ns trace-all $tracefile

# Create two nodes

set node1 [$ns node]

set node2 [$ns node]

# Define UDP agents and attach them to the nodes

set udp [new Agent/UDP]

set null [new Agent/Null]

$ns attach-agent $node1 $udp

$ns attach-agent $node2 $null

# Connect the nodes

$ns connect $udp $null

# Define traffic source (CBR)

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$cbr set packetSize_ 512

$cbr set rate_ 1Mb

# Schedule the traffic start and stop times

$ns at 1.0 “$cbr start”

$ns at 4.0 “$cbr stop”

$ns at 5.0 “finish”

# Define finish procedure

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# Run the simulation

$ns run

Analyzing the Trace File to Compute Blockage Probability:

  1. Identify Sent, Received, and Dropped Packets: In NS2 trace files:
    • Sent packets are marked with s.
    • Received packets are marked with r.
    • Dropped packets are marked with d.

Example trace entries:

s 0.500000 _1_ AGT — 512 [0 0 0 0] ——- [1:0 2:0 32 0]

r 0.550000 _2_ AGT — 512 [0 0 0 0] ——- [1:0 2:0 32 0]

d 0.520000 _2_ AGT — 512 [0 0 0 0] ——- [1:0 2:0 32 0]

    • s: Packet sent by node 1
    • r: Packet received by node 2
    • d: Packet dropped at node 2
  1. Extract Sent, Dropped, and Received Packet Information: You can use the grep and awk commands to extract the count of sent, dropped, and acquired packets from the trace file.
    • Count Sent Packets:

sent_packets=$(grep “^s” trace.tr | wc -l)

    • Count Dropped Packets:

dropped_packets=$(grep “^d” trace.tr | wc -l)

    • Total Packets: This is equivalent to the number of packets sent.
  1. Calculate Blockage Probability: The blockage probability is the ratio of dropped packets to the total number of sent packets:

blockage_probability=$(echo “scale=4; ($dropped_packets / $sent_packets)” | bc)

echo “Blockage Probability: $blockage_probability”

Example Script to Calculate Blockage Probability:

# Count the total number of packets sent

sent_packets=$(grep “^s” trace.tr | wc -l)

# Count the total number of packets dropped

dropped_packets=$(grep “^d” trace.tr | wc -l)

# Calculate the blockage probability

if [ $sent_packets -gt 0 ]; then

blockage_probability=$(echo “scale=4; ($dropped_packets / $sent_packets)” | bc)

echo “Blockage Probability: $blockage_probability”

else

echo “No packets were sent.”

fi

Summary of Steps:

  1. Configure the simulation with several nodes to simulate communication and capable blockages.
  2. Produce a trace file that logs packet-level information as well as packet transmissions and drops.
  3. Extract packet counts (sent, dropped) from the trace file using grep and awk.
  4. Calculate the blockage probability as the ratio of dropped packets to the total sent packets using the formula: Blockage Probability=Dropped PacketsSent Packets\text{Blockage Probability} = \frac{\text{Dropped Packets}}{\text{Sent Packets}}Blockage Probability=Sent PacketsDropped Packets​

Now, you can thoroughly get to know the information on how to calculate network blockage probability in ns2 by simulating a communication amongst nodes and packet transfers and how to monitor the transmission happening in the network. If you have any doubts about this computation, we will help you out of it.

Provide your parameter details, and we will compare them to give you an analysis of your project’s networking performance. To calculate the network blockage probability using the NS2 tool, we can assist you in getting the best results. Reach out to ns2project.com for excellent outcomes.