How to Calculate Network Capacity in NS2

To calculate the Network Capacity in NS2 signifies the extreme rate at which data can be transferred through the network without causing congestion, loss or degradation in performance. It can be computed based on the throughput, bandwidth consumption or the potential of the network to manage several instantaneous transmissions.

Compute the network capacity in ns2 by focusing on the parameters include aggregate throughput, bandwidth utilization or the maximum achievable data rate in various network conditions. To determine network capacity using the NS2 tool, we are here to assist you in achieving optimal results. Reach out to ns2project.com for exceptional outcomes. Our team is dedicated to sharing innovative project ideas and topics, focusing on issues related to performance loss or degradation.

The given procedure will walk you through the estimation of network capacity in ns2:

Steps to Calculate Network Capacity in NS2

  1. Generate the Trace File

Start by making sure that your NS2 script creates a trace file that records packet transmission and reception events. This trace file will help you compute network throughput, packet delivery, and other relevant metrics.

In your NS2 script, attach the following to allow trace generation:

set tracefile [open out.tr w]

$ns trace-all $tracefile

The trace file will contain entries that log when packets are delivered, obtained, or dropped.

  1. Calculate Aggregate Throughput

Throughput means that the count of data successfully transferred across the network per unit of time. Aggregate throughput considers the total data transmitted by all nodes in the network.

AWK Script to Calculate Throughput:

AWK script to extract packet sizes and compute the entire number of data acquired during the simulation. Here’s an example AWK script that calculates throughput:

awk ‘{

if ($1 == “r” && $4 == “tcp”) {

total_data += $6;  # $6 is the packet size in bytes

}

} END {

simulation_time = 100.0;  # Replace with the total simulation time in seconds

throughput = total_data / simulation_time;

print “Network Throughput: ” throughput ” bytes/second”;

}’ out.tr

  • total_data: This variable aggregates the total amount of bytes successfully acquired in the network.
  • simulation_time: Substitute this with the original duration of your simulation (in seconds).
  • throughput: This is the network throughput in bytes per second.

Throughput in Kilobits or Megabits per Second:

You can convert throughput to kilobits per second (Kbps) or megabits per second (Mbps):

throughput_kbps = throughput * 8 / 1000;  # Convert bytes to bits and then to Kbps

throughput_mbps = throughput * 8 / 1000000;  # Convert bytes to bits and then to Mbps

  1. Calculate Bandwidth Utilization

To evaluate network capacity, it’s crucial to understand how much of the existed bandwidth is being used by the network traffic.

If you know the total bandwidth of the links in your network, you can estimate bandwidth utilization as follows:

Bandwidth Utilization=Aggregate ThroughputTotal Available Bandwidth×100\text{Bandwidth Utilization} = \frac{\text{Aggregate Throughput}}{\text{Total Available Bandwidth}} \times 100Bandwidth Utilization=Total Available BandwidthAggregate Throughput​×100

For instance, if your network has a link capacity of 1 Mbps, and the aggregate throughput is 800 Kbps, the bandwidth utilization is:

Bandwidth Utilization=8001000×100=80%\text{Bandwidth Utilization} = \frac{800}{1000} \times 100 = 80\%Bandwidth Utilization=1000800​×100=80%

You can alter the AWK script to attach this calculation if you know the link capacity.

  1. Calculate Packet Delivery Ratio (PDR)

Packet Delivery Ratio (PDR) is the ratio of the number of packets successfully acquired to the number of packets delivered. High PDR values represent that the network is able to manage the traffic, which implies good network capacity.

Here’s an AWK script to calculate PDR:

awk ‘{

if ($1 == “+” && $4 == “tcp”) {

sent_packets++;

}

if ($1 == “r” && $4 == “tcp”) {

received_packets++;

}

} END {

if (sent_packets > 0) {

pdr = (received_packets / sent_packets) * 100;

print “Packet Delivery Ratio (PDR): ” pdr “%”;

} else {

print “No packets were sent.”;

}

}’ out.tr

  • A high PDR denotes that most packets are reaching their destination, suggesting the network is operating within its capacity.
  • A low PDR might signify that the network is congested or overloaded.
  1. Calculate Maximum Achievable Data Rate

The maximum achievable data rate can be evaluated by gradually maximizing the traffic load in the network (such as by rising the transmission rate of source nodes) until packet drops or delays improve significantly, representing that the network has reached its capacity.

You can adjust your NS2 script to rise the transmission rate of traffic generators (like CBR or TCP flows) and observe when packet loss begins to maximize or throughput flattens. For instance, increase the rate in the CBR application:

$ns at 0.0 “$cbr set rate_ 512Kb”   ;# Initial rate

$ns at 10.0 “$cbr set rate_ 1Mb”    ;# Increase rate after 10 seconds

$ns at 20.0 “$cbr set rate_ 2Mb”    ;# Increase rate after 20 seconds

As you rise the rate, you can see packet loss and throughput to discover the maximum achievable throughput or maximum network capacity.

  1. Calculate Link Capacity Utilization for Each Link

State the capacity utilization of separate links by assessing the trace file for transmission events amongst particular nodes. This assists identify bottlenecks in the network.

Measure the amount of data transmitted over each link by altering the AWK script. For example, to estimate how much data is transferred amongst two nodes (node 0 and node 1), use:

awk ‘{

if ($1 == “+” && $2 == 0 && $3 == 1 && $4 == “tcp”) {

link_data += $6;

}

} END {

print “Data transmitted over link 0 -> 1: ” link_data ” bytes”;

}’ out.tr

This will give you the total data transmitted through the link from node 0 to node 1.

  1. Analyze Packet Loss and Delay

Packet loss and delay are indirect pointers of network capacity. As the network approaches or surpasses its capacity, packet loss and delays will maximize because of congestion or buffer overflows.

Here’s an AWK script to calculate packet loss:

awk ‘{

if ($1 == “+” && $4 == “tcp”) {

sent_packets++;

}

if ($1 == “r” && $4 == “tcp”) {

received_packets++;

}

} END {

packet_loss = sent_packets – received_packets;

print “Packet Loss: ” packet_loss;

}’ out.tr

  1. Simulate and Analyze Network Conditions

To fully understand network capacity, you can execute various simulations under changing network conditions like:

  • Increasing traffic load (CBR or TCP rates).
  • Changing link capacities or node mobility.
  • Simulating congestion or failures (by dropping links or nodes).

Observe how these alterations impact the throughput, packet delivery, and latency. By gradually rising the traffic load, you can detect the point at which the network capacity is reached (when packet loss or delay increases significantly).

Example: Full Workflow for Network Capacity Calculation

  1. Configure the network in NS2 by configuring traffic flows, link capacities, and mobility if needed.
  2. Run the simulation and create a trace file that logs packet events.
  3. Use AWK scripts to measure:
    • Total data transmitted via the network (throughput).
    • Packet delivery ratio (PDR).
    • Packet loss and delay.
  4. Gradually increase the traffic load and see how network performance modifications.
  5. Identify the maximum throughput before the network begins dropping packets or performance degrades, representing the network’s extreme capacity.

Through the above structured process, we have utterly presented the instruction with some examples regarding the calculation of network capacity in the simulation set up using ns2 in terms of throughput, bandwidth utilization. We also provide the estimation of the required parameters.