How to Implement Network Packet Tracing in NS2

To implement the Network Packet Tracing in NS2 encompasses to log all the network events (like its packet transmission, receptions, delays and drops) in a trace file that stores the detailed behaviors of the packets. It is useful for assessing network performance, packet flow, throughput, delays and more.

NS2 has built-in support for making trace files, which can be later evaluated to understand the activities of your network simulation.

In below, we have provided the detailed process on how to implement this in ns2:

Steps to Implement Packet Tracing in NS2:

  1. Set Up the Network Topology: Configure the nodes and links for the network.
  2. Enable Tracing: NS2 offers various types of tracing (for instance: packet-level tracing, queue tracing). You need to perdefine this in your TCL script.
  3. Generate and Analyze the Trace File: The trace file records all the events for analysis.
  1. Setting Up a Simple Network Topology with Packet Tracing

Here’s an example of how to state the packet tracing in NS2 using a simple TCP simulation with two nodes.

# Create a new simulator instance

set ns [new Simulator]

# Define the output trace file for packet tracing

set tracefile [open out.tr w]

$ns trace-all $tracefile

# Define the animation file (optional, for NAM visualization)

set namfile [open out.nam w]

$ns namtrace-all $namfile

# Create network nodes (for example, two nodes n0 and n1)

set n0 [$ns node]

set n1 [$ns node]

# Create a duplex link between nodes n0 and n1 with bandwidth and delay

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

# Enable queue tracing for the link

$ns queue-limit $n0 $n1 50

# Define a TCP agent and attach it to node n0 (sender)

set tcp0 [new Agent/TCP]

$ns attach-agent $n0 $tcp0

# Define a TCP Sink (receiver) agent and attach it to node n1

set sink [new Agent/TCPSink]

$ns attach-agent $n1 $sink

# Connect the TCP agent to the TCP Sink

$ns connect $tcp0 $sink

# Define an FTP application to generate traffic over the TCP connection

set ftp [new Application/FTP]

$ftp attach-agent $tcp0

# Schedule the FTP traffic to start and stop

$ns at 1.0 “$ftp start”

$ns at 4.0 “$ftp stop”

# Set the simulation end time

$ns at 5.0 “finish”

# Define the finish procedure to close trace files and end the simulation

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam out.nam &

exit 0

}

# Run the simulation

$ns run

Explanation of the Script:

  1. Simulator Instance: set ns [new Simulator] creates an instance of the NS2 simulator.
  2. Trace File Setup:
    • The trace file is generated using the command set tracefile [open out.tr w], and tracing is enabled with $ns trace-all $tracefile. This captures all packet-level events (sending, receiving, dropping, forwarding).
    • You can also create an animation trace file for NAM (Network Animator) by stating $ns namtrace-all $namfile.
  3. Node and Link Setup:
    • Two nodes (n0 and n1) are configured, and a duplex link with bandwidth (1Mb) and delay (10ms) is set up amongst them.
    • Queue tracing is enabled for the link using $ns queue-limit $n0 $n1 50.
  4. Agent and Application Setup:
    • A TCP agent is included to node n0 (the sender) and a TCP Sink agent is added to node n1 (the receiver).
    • Use an FTP application to produce traffic over the TCP connection. The FTP traffic begins at 1.0 seconds and terminates at 4.0 seconds.
  5. Simulation Control:
    • The simulation executes for 5.0 seconds, and after that, the finish procedure is called to flush and close the trace files.
  1. Packet Tracing Options in NS2

NS2 offers numerous kinds of tracing options to capture various characteristics of the network traffic:

  • Packet-Level Tracing:
    • $ns trace-all $tracefile logs all packet-level events like sending, receiving, dispatching, and dropping packets. This has information like the event type, timestamp, source, destination, packet size, etc.
  • Queue Tracing:
    • You can trace the packet queue activities at each link using the command $ns queue-limit $n0 $n1 50, which sets a restrict for the queue and traces when packets are enqueued or dequeued.
  • Link Tracing:
    • You can define tracing for separate links using $ns trace-queue $n0 $n1.
  • Per-Node Tracing:
    • You can enable tracing for certain nodes rather than the entire network using $ns attach-agent.

Example of Trace File Output:

Here’s what a typical entry in the trace file looks like:

r 2.500000 0 1 tcp 1040 ——- 1 0.0 1.0 1020 0

s 2.500000 1 2 tcp 1040 ——- 2 0.0 1.0 1020 0

d 2.600000 1 2 tcp 1040 ——- 2 0.0 1.0 1020 0

  • First Field: Event type (r for receive, s for send, d for drop).
  • Second Field: Timestamp of the event (2.500000 seconds).
  • Third and Fourth Fields: Source and destination node IDs (0 to 1, 1 to 2, etc.).
  • Fifth Field: Protocol type (tcp in this case).
  • Sixth Field: Packet size (1040 bytes).
  • Other Fields: Has additional metadata like flow ID, packet ID, and sequence numbers.
  1. Analyzing the Trace File

Once the simulation is done, the trace file (out.tr) can be assessed to extract meaningful data like:

  • Throughput: Measure how much data was successfully transferred over time.
  • Packet Loss: Detect how many packets were dropped and at what points in the network.
  • Delay: Estimate the end-to-end delay by computing the time difference amongst when a packet is sent and received.
  • Queue Behavior: Understand how frequently packets are enqueued, dequeued, or dropped because of buffer overflow.

You can write scripts in Python, Perl, or awk to parse and analyze the trace file.

Example: Calculating Throughput Using awk

You can calculate throughput by counting the packet sizes of all successfully received (r) packets. Here’s an example of an awk script that estimates the total throughput from the trace file:

awk ‘

$1 == “r” && $4 == “tcp” {

total_bytes += $5;

}

END {

throughput = total_bytes / 5.0; # Total time in seconds

print “Throughput: ” throughput ” bytes/sec”;

}

‘ out.tr

  1. Advanced Packet Tracing
  • Per-Flow Tracing: You can filter packets in terms of flow ID or source/destination nodes to concentrate on particular traffic flows.
  • Custom Tracing: You can tailor trace formats by altering the C++ trace code in NS2 to attach more certain packet details (like headers, payload, etc.).

This procedure contains the entire information that needs to know before implementing the Packet Tracing into the network simulation using the ns2 tool. It will guide you set up the network topology and enable the tracing to establish the packet tracing. If needed, we can offer you any extra information regarding this tracing.

Let us know your needs, and we’ll provide you with more assistance. If you need extra help with implementing Packet Tracing in the NS2 tool, feel free to visit ns2project.com for further support. We also offer performance analysis services. Our team specializes in evaluating network performance, packet flow, throughput, delays, and more for your projects, and we can suggest some great project topics as well.