How to Simulate Bus Topology Projects Using NS2

To simulate a Bus Topology in NS2, you can follow these steps:

Steps to Simulate Bus Topology Projects in NS2

1. Set up NS2 Environment:

Ensure we have NS2 installed and configured appropriately on system. We can download NS2 from here. Moreover, we need a text editor to compose TCL (Tool Command Language) scripts, which NS2 utilizes for simulations.

2. Understanding Bus Topology:

• In a Bus Topology, all nodes are associated to a single communication line (the bus). Data transmit by one node is received by all other nodes, but only the designed recipient processes the data.
• In NS2, we can replicate this by configured a shared channel among all nodes.

3. Create a TCL Script for the Bus Topology:

Here’s an instance of how to generate a simple Bus Topology using NS2:

# Create a new simulator instance

set ns [new Simulator]

# Define a nam file to visualize the simulation

set nf [open out.nam w]

$ns namtrace-all $nf

# Define a shared channel (this will act as the bus)

set bus [new Channel]

# Define nodes

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

# Attach all nodes to the shared bus (channel)

$ns attach-agent $n0 $bus

$ns attach-agent $n1 $bus

$ns attach-agent $n2 $bus

$ns attach-agent $n3 $bus

# Set up traffic flow using UDP and CBR (constant bit rate)

set udp0 [new Agent/UDP]

$ns attach-agent $n0 $udp0

set cbr0 [new Application/Traffic/CBR]

$cbr0 attach-agent $udp0

$cbr0 set packetSize_ 512

$cbr0 set rate_ 100Kb

set null [new Agent/Null]

$ns attach-agent $n1 $null

# Connect the sender and receiver through the shared channel (bus)

$ns connect $udp0 $null

# Set up traffic generation

$ns at 1.0 “$cbr0 start”

$ns at 5.0 “$cbr0 stop”

# Finish simulation

$ns at 10.0 “finish”

proc finish {} {

global ns nf

$ns flush-trace

close $nf

exec nam out.nam &

exit 0

}

# Start the simulation

$ns run

4. Explanation of the Code:

• Bus Channel: The bus topology is replicated using a shared communication channel ($bus), to which all nodes are connected.
• Nodes: Nodes (n0, n1, n2, n3) are generated and attached to the shared channel.
• UDP Traffic: A UDP agent is utilized to replicate traffic from node 0 to node 1, using a CBR (Constant Bit Rate) traffic generator.
• Traffic Flow: The traffic initiates at time 1.0 seconds and ends at 5.0 seconds.
• Termination: The simulation executes until 10 seconds and is envisioning in the NAM (Network Animator) tool.

5. Run the Simulation:

1. Save the above script in a .tcl file, e.g., bus_topology.tcl.
2. Open a terminal and navigate to the folder containing script.
3. Execute the following command to run the simulation:

ns bus_topology.tcl

1. The simulation output will be saved in the out.nam file that can be opened in NAM for visualization.

We should see the bus topology in which multiple nodes interact over a shared channel.

6. Enhance the Simulation:

• We can incorporate more nodes to the bus topology by generating additional nodes and attaching them to the shared channel.
• We can also adjust traffic patterns, like introducing TCP traffic or testing with diverse data rates and packet sizes.

The given above is the fundamental approach that was illustrated with sample coding for Bus Topology project that were simulated across the ns2 environment. We plan to deliver more information regarding this project in further manual.

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