To simulate a Daisy Chain Topology in NS2, we need to configure a linear sequence of nodes in which each node is associated to exactly two others, except for the two endpoints. Data flows from one node to another across the chain.
Here’s how to simulate a Daisy Chain Topology in NS2:
Steps to Simulate Daisy Chain Topology Projects in NS2
- Set up NS2 Environment:
Make sure that NS2 is installed and functioning on the system. The simulation will be completed using a TCL script.
- Understanding Daisy Chain Topology:
- In a Daisy Chain Topology, nodes are associated in series, in which the data flows in a straight path, usually from one node to another until it reaches its destination.
- Nodes are associated in a sequence, with each node (except the first and last) having two connections — one to its predecessor and one to its successor.
- Create a TCL Script for Daisy Chain Topology:
Below is an sample of a Daisy Chain Topology simulation in NS2:
# Create a new simulator instance
set ns [new Simulator]
# Open a NAM trace file for visualization
set nf [open out.nam w]
$ns namtrace-all $nf
# Create nodes (forming a chain)
set n0 [$ns node] ;# First node (endpoint)
set n1 [$ns node] ;# Intermediate node 1
set n2 [$ns node] ;# Intermediate node 2
set n3 [$ns node] ;# Intermediate node 3
set n4 [$ns node] ;# Last node (endpoint)
# Create duplex links to form the Daisy Chain
$ns duplex-link $n0 $n1 10Mb 10ms DropTail
$ns duplex-link $n1 $n2 10Mb 10ms DropTail
$ns duplex-link $n2 $n3 10Mb 10ms DropTail
$ns duplex-link $n3 $n4 10Mb 10ms DropTail
# Create a UDP agent and attach it to the first node (n0)
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
# Create a Null agent and attach it to the last node (n4)
set null0 [new Agent/Null]
$ns attach-agent $n4 $null0
# Connect the UDP agent (n0) to the Null agent (n4)
$ns connect $udp0 $null0
# Create a Constant Bit Rate (CBR) traffic generator and attach it to the UDP agent
set cbr0 [new Application/Traffic/CBR]
$cbr0 attach-agent $udp0
$cbr0 set packetSize_ 512 ;# Packet size of 512 bytes
$cbr0 set rate_ 100Kb ;# Data rate of 100Kb
# Schedule the CBR traffic to start and stop
$ns at 1.0 “$cbr0 start” ;# Start traffic at 1 second
$ns at 5.0 “$cbr0 stop” ;# Stop traffic at 5 seconds
# End the simulation at 6 seconds
$ns at 6.0 “finish”
proc finish {} {
global ns nf
$ns flush-trace
close $nf
exec nam out.nam &
exit 0
}
# Run the simulation
$ns run
- Explanation of the Code:
- Nodes: Five nodes are created (n0, n1, n2, n3, and n4) to form the daisy chain. Node n0 is the starting point, and node n4 is the endpoint.
- Links: Duplex links are configures among consecutive nodes to generate the chain, with a bandwidth of 10Mb and a latency of 10ms for each link.
- UDP Traffic: A UDP agent is generated at node n0 (the starting node) to transmit data, and a Null agent is generated at node n4 (the endpoint) to receive the traffic.
- Traffic Generator (CBR): A Constant Bit Rate (CBR) traffic generator transmit packets of 512 bytes at a rate of 100Kb from n0 to n4.
- Scheduling Traffic: The traffic initiate at 1 second and terminate at 5 seconds, and the simulation stops at 6 seconds.
- Run the Simulation:
- Save the script as daisy_chain.tcl.
- Open a terminal and navigate to the folder in which the script is saved.
- Execute the simulation using the following command:
ns daisy_chain.tcl
- The output will create an out.nam file that can be opened using the Network Animator (NAM) tool.
- Visualization in NAM:
- After the simulation executes, we can envision the daisy chain topology using the Network Animator (NAM). The nodes will perform in a linear arrangement, and we will monitor the traffic flowing from n0 to n4 through the intermediate nodes (n1, n2, and n3).
- Customization and Enhancements:
- TCP Traffic: We can replace the UDP agent with a TCP agent to replicate reliable data transmission. For example:
set tcp0 [new Agent/TCP]
$ns attach-agent $n0 $tcp0
set sink0 [new Agent/TCPSink]
$ns attach-agent $n4 $sink0
$ns connect $tcp0 $sink0
- More Nodes: We can expand the daisy chain by incorporating more nodes and duplex links.
- Different Bandwidth/Delay: Adjust the duplex link metrics to test with different network conditions such as higher bandwidth or longer delays.
- Multiple Flows: We can incorporate additional traffic flows, like sending traffic from node n4 back to n0 or among any other pairs of nodes.
- Performance Metrics: We can increase trace files to evaluate parameters such as packet loss, delay, and throughput. For example:
set tracefile [open trace.tr w]
$ns trace-all $tracefile
- Performance Analysis:
To measure the performance of the Daisy Chain Topology, we can:
- Evaluate throughput by measuring the amount of data successfully routed among nodes.
- Evaluate the latency (delay) as data travels from one node to another via the chain.
- Validate for packet loss if the network is congested or the data rate surpasses the link capacity.
This project idea deliver wide range of implementations using the Daisy Chain Topology in NS2, helping you explore numerous contexts of the topology performance in scenarios. We plan to deliver the detailed instructions to these projects to in further manual.
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