Sending Traffics Through NS2 Links

1. Introduction to wired networks: In a wired network, nodes are connected to each other through physical cables. This network provides high speed and reliability, so that large-scale data transmission can be done without any interruption. NS2 is used to simulate this process.

2. Simulation setup: A simulation setup is required to send data between nodes in a wired network. The simulation setup includes the process of creating nodes, establishing links between them, and connecting traffic agents to the nodes.

3. Creating the simulator and nodes: First, you need to create a simulator object and nodes in NS2:

# Creating the simulator object

set ns [new Simulator]

# Creating the nodes

set node1 [$ns node]

set node2 [$ns node]

set node3 [$ns node]

Here, we have created three nodes (node1, node2, and node3), which we will link together later.

4. Establishing links: Now, it is necessary to create physical links between the nodes. In NS2, you can connect the nodes using the duplex-link command and determine the characteristics of the link, such as bandwidth and latency.

# Creating links between the nodes

$ns duplex-link $node1 $node2 1Mb 10ms DropTail

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

In this:

1Mb represents the bandwidth, i.e., the speed of data transfer.

10ms represents the latency, i.e., the time it takes for data to reach from one node to another.

DropTail is a queue management policy that states that if the queue becomes full, new packets will be dropped.

5. Creating and attaching agents: To send data, we need to connect traffic agents to the nodes. Generally, TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) agents are used. For example, we can use TCP:

# Creating a TCP agent

set tcp0 [new Agent/TCP]

$ns attach-agent $node1 $tcp0

# Connecting the TCP agent to another node

set sink [new Agent/TCPSink]

$ns attach-agent $node2 $sink

In this:

tcp0 is a TCP agent that is attached to node1.

sink is a TCP Sink agent, which is attached to node2 and will receive TCP data.

6. Traffic generation: Now, you need to generate traffic, so that data packets can be exchanged between the nodes. For this, you will need to use a traffic pattern, such as FTP or CBR (Constant Bit Rate). Example:

# Connecting the FTP application to the TCP agent

set ftp [new Application/FTP]

$ftp attach-agent $tcp0

$ns at 1.0 "$ftp start"

$ns at 5.0 "$ftp stop"

In this:

The FTP (File Transfer Protocol) application is connected to the tcp0 agent, which will send data from node1.

The data transfer will start at 1 second of simulation time and stop at 5 seconds.

7. Setting the simulation time and running it: Once all the nodes, agents, and traffic are set, you need to set the simulation time and then run the simulation.

# Simulation end time

$ns at 6.0 "finish"

proc finish {} {

    global ns

    $ns halt

}

# Running the simulation

$ns run

This simulation will run for 6 seconds and then end.

8. Tracing and NAM animation: You can create a trace file to trace the traffic during the simulation, which can be used for analysis later. You can also use NAM (Network Animator) to see the network animation:

# Creating a trace file

set tracefile [open out.tr w]

$ns trace-all $tracefile

# Creating a NAM animation file

set namfile [open out.nam w]

$ns namtrace-all $namfile

9. Analysis of results: After the simulation, the trace file can be analyzed, from which you can see various parameters such as packet transfer, latency, packet loss, and throughput. You can also observe the network activities through a graphical interface by running the NAM file.